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I was thinking...my next pcb will be simple but will be all SMT components for my first time. I was curious if it is ok to put one circuit on one side of the 2 sided boards, and another on the other side? They would be 2 simple, yet different circuits. Is that something that has been done before? Is that kosher with the pcb makers that will make the board? Or is that cheating? In the end it would be a choice of what side to use by me and only one side would ever be used.
Thanks,
Dave
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The answer is a qualified yes.? Most circuits use top and bottom parts with vias as needed.
However, you need to consider that the two circuits are going to be less than 1/16 of an inch apart, and then consider crosstalk between the two circuits.? If you were doing a 4 layer board, the ground and power planes would tend to act like ground planes, and you'd have less problems.? You don't, though.
The PC board makers don't know, and don't care what you do.? All they care is if (according to their rules) they can manufacture the board.? Shorts?? Overlapping ground planes?? bad labels? reversed connectors?? They don't know, and frankly, they don't care. Cheating for the manufacturers is that the there are two different designs on the? same board, separate (I think) and not connected any way to each other.? (or, I bet, two designs separated by a snap off, if they can do that).
Since you don't use both sides, then I'd do a ground pour on both sides, and that of course, would weld both circuits together. It's the same thing as a construction variant, where you either install a part or not.? They won't care.
Now, if you have a small circuit board, say you can fit more than one on a 100 mm by 100 mm board, you can duplicate the pattern (in EAGLE, one way is to close the board, then copy and paste the board pattern).? Go completely across the board with lines on the milling layer, and you can have multiple designs (same design) on the same produced plate.
Got more LED strips to substitute for backlights than I care to think about.? LED (1206) and resistor (0805) on the other.? About nine LEDS on a side.? Length determined by the 100 mm cheapie limit.
Harvey
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On 11/11/2020 6:07 PM, Dave wrote: I was thinking...my next pcb will be simple but will be all SMT components for my first time. I was curious if it is ok to put one circuit on one side of the 2 sided boards, and another on the other side? They would be 2 simple, yet different circuits. Is that something that has been done before? Is that kosher with the pcb makers that will make the board? Or is that cheating? In the end it would be a choice of what side to use by me and only one side would ever be used.
Thanks,
Dave
|
Thanks for the info Harvey. On 11/11/2020 6:23 PM, Harvey White wrote: The answer is a qualified yes.? Most circuits use top and bottom parts with vias as needed. Great. Even though SMT uses less space and I could do multiple paths on one side, I see the other side a waste of space.
However, you need to consider that the two circuits are going to be less than 1/16 of an inch apart, and then consider crosstalk between the two circuits.? If you were doing a 4 layer board, the ground and power planes would tend to act like ground planes, and you'd have less problems.? You don't, though.
You are correct as this will not affect me.
The PC board makers don't know, and don't care what you do.? All they care is if (according to their rules) they can manufacture the board.? Shorts?? Overlapping ground planes?? bad labels? reversed connectors?? They don't know, and frankly, they don't care. Cheating for the manufacturers is that the there are two different designs on the? same board, separate (I think) and not connected any way to each other.? (or, I bet, two designs separated by a snap off, if they can do that).
You can make boards , like you say, that are panelized but in my case that costs more and in not needed.
Since you don't use both sides, then I'd do a ground pour on both sides, and that of course, would weld both circuits together. It's the same thing as a construction variant, where you either install a part or not.? They won't care.
How would that weld the two circuits together unless I ad a via? Will a thru hole for mounting it to a standoff act as a via?
Now, if you have a small circuit board, say you can fit more than one on a 100 mm by 100 mm board, you can duplicate the pattern (in EAGLE, one way is to close the board, then copy and paste the board pattern).? Go completely across the board with lines on the milling layer, and you can have multiple designs (same design) on the same produced plate.
I have done that with design spark in the past but cut the paper to laminate it to my pcb copper boards (single sided). But now after paying only $18 ( $36 with shipping as I paid for speedier method ) for 200 of my first batch of small simple pcb's, I am going to have them made from now on.
Got more LED strips to substitute for backlights than I care to think about.? LED (1206) and resistor (0805) on the other.? About nine LEDS on a side.? Length determined by the 100 mm cheapie limit.
I am going to start with 1206 resistors. Thanks, Dave
Harvey
On 11/11/2020 6:07 PM, Dave wrote:
I was thinking...my next pcb will be simple but will be all SMT components for my first time. I was curious if it is ok to put one circuit on one side of the 2 sided boards, and another on the other side? They would be 2 simple, yet different circuits. Is that something that has been done before? Is that kosher with the pcb makers that will make the board? Or is that cheating? In the end it would be a choice of what side to use by me and only one side would ever be used.
Thanks,
Dave
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replies interleaved. On 11/12/2020 11:03 AM, Dave wrote: Thanks for the info Harvey.
On 11/11/2020 6:23 PM, Harvey White wrote:
The answer is a qualified yes.? Most circuits use top and bottom parts with vias as needed. Great. Even though SMT uses less space and I could do multiple paths on one side, I see the other side a waste of space.
The other side does not become a waste of space with more complicated circuits.? Nor, if you're doing high frequency digital stuff, is the idea of a ground plane on the back a bad idea.? I *really* use both sides of the board.? If what you're doing is simple enough, then you can successfully route the board using one side only. However, you need to consider that the two circuits are going to be less than 1/16 of an inch apart, and then consider crosstalk between the two circuits.? If you were doing a 4 layer board, the ground and power planes would tend to act like ground planes, and you'd have less problems.? You don't, though. You are correct as this will not affect me.
The PC board makers don't know, and don't care what you do.? All they care is if (according to their rules) they can manufacture the board.? Shorts?? Overlapping ground planes?? bad labels? reversed connectors?? They don't know, and frankly, they don't care. Cheating for the manufacturers is that the there are two different designs on the? same board, separate (I think) and not connected any way to each other.? (or, I bet, two designs separated by a snap off, if they can do that).
You can make boards , like you say, that are panelized but in my case that costs more and in not needed.
I used SeeedStudio fabrication, which goes from EAGLE (they provide a CAM batch job to go to gerbers) almost directly.? Their price is 4.90 for any size HASL board, silk screened both sides, plated through holes up to 100 mm by 100 mm.? By designing the circuit with separate inputs and outputs (sides as appropriate), having a common ground pour, the circuits are essentially the same circuit I'd think, as far as they're concerned.? So for panelization, definitely no penalty.
Since you don't use both sides, then I'd do a ground pour on both sides, and that of course, would weld both circuits together. It's the same thing as a construction variant, where you either install a part or not.? They won't care.
How would that weld the two circuits together unless I ad a via? Will a thru hole for mounting it to a standoff act as a via?
Ground is ground, VCC is VCC, if they're the same it makes your layout easier, perhaps.
Now, if you have a small circuit board, say you can fit more than one on a 100 mm by 100 mm board, you can duplicate the pattern (in EAGLE, one way is to close the board, then copy and paste the board pattern).? Go completely across the board with lines on the milling layer, and you can have multiple designs (same design) on the same produced plate.
I have done that with design spark in the past but cut the paper to laminate it to my pcb copper boards (single sided). But now after paying only $18 ( $36 with shipping as I paid for speedier method ) for 200 of my first batch of small simple pcb's, I am going to have them made from now on.
I can understand that one.? Sadly, the designs I do tend to be a bit more complex.
Got more LED strips to substitute for backlights than I care to think about.? LED (1206) and resistor (0805) on the other. About nine LEDS on a side.? Length determined by the 100 mm cheapie limit.
I am going to start with 1206 resistors.
Decent enough, then, as I found, 0805 make for more parts on the board where needed. Harvey Thanks,
Dave
Harvey
On 11/11/2020 6:07 PM, Dave wrote:
I was thinking...my next pcb will be simple but will be all SMT components for my first time. I was curious if it is ok to put one circuit on one side of the 2 sided boards, and another on the other side? They would be 2 simple, yet different circuits. Is that something that has been done before? Is that kosher with the pcb makers that will make the board? Or is that cheating? In the end it would be a choice of what side to use by me and only one side would ever be used.
Thanks,
Dave
|
Harvey,
? I have a related question here after spending some time researching. I already have a bunch of JST XH connectors and plugs, and pins and the crimper. I wanted to design a total SMT pcb and I could solder the power and ground wires to a pad. Then I thought about adding a JST header and use a plug for power and ground. Problem is, the JST parts are all through hole. So now for my question ( I may have a clue but will ask anyhow to verify ), what is the best method on the board design to use through hole and SMT at the same time? Will I still be able to do my planned 2 different circuits on either side of the board? How should I handle the power header? Use it to supply both sides of the board with one header or use 2 headers for power/GND and separate the copper with islands?
Thanks,
Dave
|
Interleaved. On 11/13/2020 1:11 PM, Dave wrote: Harvey,
? I have a related question here after spending some time researching. I already have a bunch of JST XH connectors and plugs, and pins and the crimper. Instead of JST, I use 0.1 inch spacing connectors.? The female/female jumpers can be tweaked to remove the individual shrouds, and can be reinserted in strip connectors to make some decent cables.? JST will work fine, but I've found them tricky to use.? I'd just as soon look for premade cables.? Your luck with the crimper (I hope) will be better than mine. I wanted to design a total SMT pcb and I could solder the power and ground wires to a pad. Then I thought about adding a JST header and use a plug for power and ground. That works. Problem is, the JST parts are all through hole. So now for my question ( I may have a clue but will ask anyhow to verify ), what is the best method on the board design to use through hole and SMT at the same time? I just put them in and let the router do its work.? For your design, you might want to have separate power pins if the supplies are different, say that if you need +5 for the top circuit and +12 for the lower one, have a power connector with separate pins for the two supplies.? That keeps the power supplies from being mixed. Will I still be able to do my planned 2 different circuits on either side of the board? How should I handle the power header? Use it to supply both sides of the board with one header or use 2 headers for power/GND and separate the copper with islands?
?Given a common ground for both circuits (which works), you're running separate supplies from separate pins, so just one connector and wire it appropriately depending on which circuit you're doing.? You can use unused parts of the other side as jumpers.? If you don't want to do that, you can use 0 ohm resistors (1206 works best just because of the size).? it's easier than running wire jumpers. So yes, one power/signal connector can do the job if you think that the inputs/outputs don't make for too large a connector If you have a lot of inputs and outputs, there's two ways to do this: one is to have a separate power connector (and have separate pins for each supply rather than one "power" pin), and then separate connectors for each circuit.? I'd use different size connectors to avoid misconnections. two is to have power and signals on one connector (perhaps few pins for signals) not sharing any pins except ground and identical power supply voltages. Harvey Thanks,
Dave
|
It depends entirely on your needs. If you need to power both circuits
simultaneously, then (obviously) you need to connect power supply and
return (it's not ground unless it is really attached to the safety
ground somewhere) to both simultaneously. If they are always going to be
operating separately but always both populated, then it might be wise to
have two connectors (one for each side.) If only one side of the board
is to be populated (I don't remember the original post) then connecting
to both simultaneously would make sense, unless power routing for one
side would be compromised by this decision.
HTH,
Donald.
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On 2020-11-13 1:11 p.m., Dave wrote: Harvey,
? I have a related question here after spending some time researching. I
already have a bunch of JST XH connectors and plugs, and pins and the
crimper. I wanted to design a total SMT pcb and I could solder the power
and ground wires to a pad. Then I thought about adding a JST header and
use a plug for power and ground. Problem is, the JST parts are all
through hole. So now for my question ( I may have a clue but will ask
anyhow to verify ), what is the best method on the board design to use
through hole and SMT at the same time? Will I still be able to do my
planned 2 different circuits on either side of the board? How should I
handle the power header? Use it to supply both sides of the board with
one header or use 2 headers for power/GND and separate the copper with
islands?
Thanks,
Dave
|
Donald,
? My needs are still simple as I am just getting started with SMT and pcb's at limited times due to too many hobbies and other work. :) Simple led circuits and my last through hole pcb just allowed to make a series or a parallel circuit depending on how I populated it. This worked great. Now with the SMT version I supposed I could do the same trick and populate accordingly but figured the second side would be blank so why not use it. I guess I jest need to learn a few more things and maybe this is where the VIA comes in. Never used one but isn't that just a jumper from side A to B? And back to my circuits...I don't have any JST SMT headers but I have some through hole ones. So with a mix of through hole and SMT I was just concerned about doing it right with the power and ground. Only one side will ever be used and populated with anything. That said, I believe you already answered my question.
Thanks,
Dave
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Show quoted text
On 11/13/2020 12:53 PM, Donald H Locker wrote: It depends entirely on your needs. If you need to power both circuits
simultaneously, then (obviously) you need to connect power supply and
return (it's not ground unless it is really attached to the safety
ground somewhere) to both simultaneously. If they are always going to be
operating separately but always both populated, then it might be wise to
have two connectors (one for each side.) If only one side of the board
is to be populated (I don't remember the original post) then connecting
to both simultaneously would make sense, unless power routing for one
side would be compromised by this decision.
HTH,
Donald.
--
*Plain Text* email -- it's an accessibility issue
() no proprietary attachments; no html mail
/\ <>
On 2020-11-13 1:11 p.m., Dave wrote:
Harvey,
? I have a related question here after spending some time researching. I
already have a bunch of JST XH connectors and plugs, and pins and the
crimper. I wanted to design a total SMT pcb and I could solder the power
and ground wires to a pad. Then I thought about adding a JST header and
use a plug for power and ground. Problem is, the JST parts are all
through hole. So now for my question ( I may have a clue but will ask
anyhow to verify ), what is the best method on the board design to use
through hole and SMT at the same time? Will I still be able to do my
planned 2 different circuits on either side of the board? How should I
handle the power header? Use it to supply both sides of the board with
one header or use 2 headers for power/GND and separate the copper with
islands?
Thanks,
Dave
|
Interleaved some more. On 11/13/2020 12:53 PM, Harvey White wrote: Interleaved.
On 11/13/2020 1:11 PM, Dave wrote:
Harvey,
? I have a related question here after spending some time researching. I already have a bunch of JST XH connectors and plugs, and pins and the crimper. Instead of JST, I use 0.1 inch spacing connectors.? The female/female jumpers can be tweaked to remove the individual shrouds, and can be reinserted in strip connectors to make some decent cables.? JST will work fine, but I've found them tricky to use.? I'd just as soon look for premade cables.? Your luck with the crimper (I hope) will be better than mine. ??????????? The .1 inch (2.54mm) spacing should work ok with the JST 2.5mm spacing, at least for short length stuff. SO I should be good there. I did look at premade cables but noticed nobody bragging about 100% copper and after researching deeper found most use copper clad aluminum. I hate that stuff as I need to cut the cables and solder one end elsewhere. I have had good enough luck with the JST crimping but have another crimper on my list to order.
I wanted to design a total SMT pcb and I could solder the power and ground wires to a pad. Then I thought about adding a JST header and use a plug for power and ground. That works.
??????????? Except I don't have any SMT headers in JST XH and although they are available, they come in a 3 circuit style and a 4 and a 5. I really only wanted a 2 circuit version but I have that in a through hole and its also a 90 degree version to save some space on the enclosure height,.
Problem is, the JST parts are all through hole. So now for my question ( I may have a clue but will ask anyhow to verify ), what is the best method on the board design to use through hole and SMT at the same time? I just put them in and let the router do its work.? For your design, you might want to have separate power pins if the supplies are different, say that if you need +5 for the top circuit and +12 for the lower one, have a power connector with separate pins for the two supplies.? That keeps the power supplies from being mixed.
??????????? I guess I was worried about the power feeding the top side while being soldered to the bottom side. I figured I had to have a jumper from the bottom back to the top but now that I think of it, the holes would be plated thru holes...
Will I still be able to do my planned 2 different circuits on either side of the board? How should I handle the power header? Use it to supply both sides of the board with one header or use 2 headers for power/GND and separate the copper with islands?
?Given a common ground for both circuits (which works), you're running separate supplies from separate pins, so just one connector and wire it appropriately depending on which circuit you're doing.? You can use unused parts of the other side as jumpers.? If you don't want to do that, you can use 0 ohm resistors (1206 works best just because of the size).? it's easier than running wire jumpers.
So yes, one power/signal connector can do the job if you think that the inputs/outputs don't make for too large a connector
If you have a lot of inputs and outputs, there's two ways to do this:
one is to have a separate power connector (and have separate pins for each supply rather than one "power" pin), and then separate connectors for each circuit.? I'd use different size connectors to avoid misconnections.
two is to have power and signals on one connector (perhaps few pins for signals) not sharing any pins except ground and identical power supply voltages.
??????????? I didn't even know they made "0" ohm resistors. But I am starting to understand it now. I guess I will start to design it and then in the software things will become obvious. Thanks, Dave
Harvey
Thanks,
Dave
|
yet more replies..... On 11/13/2020 3:42 PM, Dave wrote: Interleaved some more.
On 11/13/2020 12:53 PM, Harvey White wrote:
Interleaved.
On 11/13/2020 1:11 PM, Dave wrote:
Harvey,
? I have a related question here after spending some time researching. I already have a bunch of JST XH connectors and plugs, and pins and the crimper. Instead of JST, I use 0.1 inch spacing connectors.? The female/female jumpers can be tweaked to remove the individual shrouds, and can be reinserted in strip connectors to make some decent cables.? JST will work fine, but I've found them tricky to use.? I'd just as soon look for premade cables.? Your luck with the crimper (I hope) will be better than mine. ??????????? The .1 inch (2.54mm) spacing should work ok with the JST 2.5mm spacing, at least for short length stuff. SO I should be good there. I did look at premade cables but noticed nobody bragging about 100% copper and after researching deeper found most use copper clad aluminum. I hate that stuff as I need to cut the cables and solder one end elsewhere. I have had good enough luck with the JST crimping but have another crimper on my list to order. It's ok.? You just don't want to mix the 2 mm and 2.54 mm stuff. I generally use 0.1 inch spacing because that's easy to find.? The 2.0 mm(or less) JST I use where someone else used it.
I wanted to design a total SMT pcb and I could solder the power and ground wires to a pad. Then I thought about adding a JST header and use a plug for power and ground. That works.
??????????? Except I don't have any SMT headers in JST XH and although they are available, they come in a 3 circuit style and a 4 and a 5. I really only wanted a 2 circuit version but I have that in a through hole and its also a 90 degree version to save some space on the enclosure height,.
Ok, here's a trick.? I use 5.0 volts as a bulk supply and on each board, typically regulate it to 3.3 volts (this is mostly microprocessor stuff and 3.3 volt modules.? I use 3 pin power connectors (in red) with the inner pin being ground and the outer two pins being +5.? You can't reverse polarity the board except by getting the connector one pin off. I use through hole connectors.? It doesn't do anything bad except to eat up a little board space.? Remember that on a 90 degree connector, you trade off width for height, and it can make a difference. Where possible, I make some of the connections symmetric like that.? It costs extra pins, but saves some problems.
Problem is, the JST parts are all through hole. So now for my question ( I may have a clue but will ask anyhow to verify ), what is the best method on the board design to use through hole and SMT at the same time? I just put them in and let the router do its work.? For your design, you might want to have separate power pins if the supplies are different, say that if you need +5 for the top circuit and +12 for the lower one, have a power connector with separate pins for the two supplies.? That keeps the power supplies from being mixed.
??????????? I guess I was worried about the power feeding the top side while being soldered to the bottom side. I figured I had to have a jumper from the bottom back to the top but now that I think of it, the holes would be plated thru holes...
The holes are plated through holes.? Using EAGLE, for instance, you route on the top layer, then change to the bottom layer, you'll see the trace turn blue and a via put in at the last place the trace stopped.? Continue to route on the bottom of the board, and change layers again to get back to the top layer.? Since you don't mount boards directly on a conductive metal plate, it shouldn't matter if there is live power on the other side of the board.? That would be normal for any board. Using the example where you have absolutely no connections between board sides, if you had a single power connector, the top and bottom grounds and power (if the same voltage) would be connected at the through holes on the connector.
Will I still be able to do my planned 2 different circuits on either side of the board? How should I handle the power header? Use it to supply both sides of the board with one header or use 2 headers for power/GND and separate the copper with islands?
?Given a common ground for both circuits (which works), you're running separate supplies from separate pins, so just one connector and wire it appropriately depending on which circuit you're doing.? You can use unused parts of the other side as jumpers.? If you don't want to do that, you can use 0 ohm resistors (1206 works best just because of the size).? it's easier than running wire jumpers.
So yes, one power/signal connector can do the job if you think that the inputs/outputs don't make for too large a connector
If you have a lot of inputs and outputs, there's two ways to do this:
one is to have a separate power connector (and have separate pins for each supply rather than one "power" pin), and then separate connectors for each circuit.? I'd use different size connectors to avoid misconnections.
two is to have power and signals on one connector (perhaps few pins for signals) not sharing any pins except ground and identical power supply voltages.
??????????? I didn't even know they made "0" ohm resistors. But I am starting to understand it now. I guess I will start to design it and then in the software things will become obvious.
I think so.? EAGLE's autorouter makes assumptions with their standard setups that are good for having the boards manufactured, but not good for things like toner transfer boards (10/10; 10 mil traces and 10 mil spacing between conductors are workable).? If you're making boards, you need one setup.? If you're having boards made, then use their recommended setups and you're fine. This is likely true with any other layout program.? Your PCB layout program will automatically (or should) insert a via when you change layers. Harvey Thanks,
Dave
Harvey
Thanks,
Dave
|
Thanks Harvey. It all makes perfect sense now that I remembered the VIA. One bonus round question. What if you wanted to reverse the polarity and you had a connector ( 2 pin ) that was "keyed" so you couldn't just unplug and re-plug it in the opposite way? Like with a JST XH series. I know with a standard 0.1 header pins that wouldn't be a problem but are there any tricks to make that happen? Just curious because us noobs ask the strangest questions and sometimes they are good ones.
Thanks,
Dave
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On 11/13/2020 4:46 PM, Harvey White wrote: yet more replies.....
On 11/13/2020 3:42 PM, Dave wrote:
Interleaved some more.
On 11/13/2020 12:53 PM, Harvey White wrote:
Interleaved.
On 11/13/2020 1:11 PM, Dave wrote:
Harvey,
? I have a related question here after spending some time researching. I already have a bunch of JST XH connectors and plugs, and pins and the crimper. Instead of JST, I use 0.1 inch spacing connectors.? The female/female jumpers can be tweaked to remove the individual shrouds, and can be reinserted in strip connectors to make some decent cables.? JST will work fine, but I've found them tricky to use.? I'd just as soon look for premade cables. Your luck with the crimper (I hope) will be better than mine. ??????????? The .1 inch (2.54mm) spacing should work ok with the JST 2.5mm spacing, at least for short length stuff. SO I should be good there. I did look at premade cables but noticed nobody bragging about 100% copper and after researching deeper found most use copper clad aluminum. I hate that stuff as I need to cut the cables and solder one end elsewhere. I have had good enough luck with the JST crimping but have another crimper on my list to order. It's ok.? You just don't want to mix the 2 mm and 2.54 mm stuff. I generally use 0.1 inch spacing because that's easy to find.? The 2.0 mm(or less) JST I use where someone else used it.
I wanted to design a total SMT pcb and I could solder the power and ground wires to a pad. Then I thought about adding a JST header and use a plug for power and ground. That works.
??????????? Except I don't have any SMT headers in JST XH and although they are available, they come in a 3 circuit style and a 4 and a 5. I really only wanted a 2 circuit version but I have that in a through hole and its also a 90 degree version to save some space on the enclosure height,.
Ok, here's a trick.? I use 5.0 volts as a bulk supply and on each board, typically regulate it to 3.3 volts (this is mostly microprocessor stuff and 3.3 volt modules.? I use 3 pin power connectors (in red) with the inner pin being ground and the outer two pins being +5.? You can't reverse polarity the board except by getting the connector one pin off.
I use through hole connectors.? It doesn't do anything bad except to eat up a little board space.? Remember that on a 90 degree connector, you trade off width for height, and it can make a difference.
Where possible, I make some of the connections symmetric like that.? It costs extra pins, but saves some problems.
Problem is, the JST parts are all through hole. So now for my question ( I may have a clue but will ask anyhow to verify ), what is the best method on the board design to use through hole and SMT at the same time? I just put them in and let the router do its work.? For your design, you might want to have separate power pins if the supplies are different, say that if you need +5 for the top circuit and +12 for the lower one, have a power connector with separate pins for the two supplies.? That keeps the power supplies from being mixed.
??????????? I guess I was worried about the power feeding the top side while being soldered to the bottom side. I figured I had to have a jumper from the bottom back to the top but now that I think of it, the holes would be plated thru holes...
The holes are plated through holes.? Using EAGLE, for instance, you route on the top layer, then change to the bottom layer, you'll see the trace turn blue and a via put in at the last place the trace stopped.? Continue to route on the bottom of the board, and change layers again to get back to the top layer.? Since you don't mount boards directly on a conductive metal plate, it shouldn't matter if there is live power on the other side of the board.? That would be normal for any board.
Using the example where you have absolutely no connections between board sides, if you had a single power connector, the top and bottom grounds and power (if the same voltage) would be connected at the through holes on the connector.
Will I still be able to do my planned 2 different circuits on either side of the board? How should I handle the power header? Use it to supply both sides of the board with one header or use 2 headers for power/GND and separate the copper with islands?
?Given a common ground for both circuits (which works), you're running separate supplies from separate pins, so just one connector and wire it appropriately depending on which circuit you're doing.? You can use unused parts of the other side as jumpers.? If you don't want to do that, you can use 0 ohm resistors (1206 works best just because of the size).? it's easier than running wire jumpers.
So yes, one power/signal connector can do the job if you think that the inputs/outputs don't make for too large a connector
If you have a lot of inputs and outputs, there's two ways to do this:
one is to have a separate power connector (and have separate pins for each supply rather than one "power" pin), and then separate connectors for each circuit.? I'd use different size connectors to avoid misconnections.
two is to have power and signals on one connector (perhaps few pins for signals) not sharing any pins except ground and identical power supply voltages.
??????????? I didn't even know they made "0" ohm resistors. But I am starting to understand it now. I guess I will start to design it and then in the software things will become obvious.
I think so.? EAGLE's autorouter makes assumptions with their standard setups that are good for having the boards manufactured, but not good for things like toner transfer boards (10/10; 10 mil traces and 10 mil spacing between conductors are workable).? If you're making boards, you need one setup.? If you're having boards made, then use their recommended setups and you're fine.
This is likely true with any other layout program.? Your PCB layout program will automatically (or should) insert a via when you change layers.
Harvey
Thanks,
Dave
Harvey
Thanks,
Dave
|
If the connector is keyed, and you really can't plug it in backwards, then you don't need symmetric pins.? Some connectors can be forced in backwards.
There are keys that fit into the connector in place of a socket. The mating pin needs to be removed.? I might try to 3D print some of them, but the best solution might be to go to a hobby shop and get some very thin plastic that could fit into the connector from the back to block the pin being inserted.
I've tried finding them, but they seem to be rather expensive, where they are available.
So for connectors where the body is not keyed, you need to key the pins if it's important.? Another method would be to put power and ground in such locations that plugging the connector in backwards doesn't connect nasty signals (like outputs to outputs), power to ground, etc.? This takes some careful work and may not always be possible.
The symmetric method is workable, and you may end up thinking of 3D printing your own shrouds for the on board pins to keep the plug from being inserted off by a pin (or just key it).
Harvey
toggle quoted message
Show quoted text
On 11/13/2020 6:18 PM, Dave wrote: Thanks Harvey. It all makes perfect sense now that I remembered the VIA. One bonus round question. What if you wanted to reverse the polarity and you had a connector ( 2 pin ) that was "keyed" so you couldn't just unplug and re-plug it in the opposite way? Like with a JST XH series. I know with a standard 0.1 header pins that wouldn't be a problem but are there any tricks to make that happen? Just curious because us noobs ask the strangest questions and sometimes they are good ones.
Thanks,
Dave
On 11/13/2020 4:46 PM, Harvey White wrote:
yet more replies.....
On 11/13/2020 3:42 PM, Dave wrote:
Interleaved some more.
On 11/13/2020 12:53 PM, Harvey White wrote:
Interleaved.
On 11/13/2020 1:11 PM, Dave wrote:
Harvey,
? I have a related question here after spending some time researching. I already have a bunch of JST XH connectors and plugs, and pins and the crimper. Instead of JST, I use 0.1 inch spacing connectors.? The female/female jumpers can be tweaked to remove the individual shrouds, and can be reinserted in strip connectors to make some decent cables.? JST will work fine, but I've found them tricky to use.? I'd just as soon look for premade cables. Your luck with the crimper (I hope) will be better than mine. ??????????? The .1 inch (2.54mm) spacing should work ok with the JST 2.5mm spacing, at least for short length stuff. SO I should be good there. I did look at premade cables but noticed nobody bragging about 100% copper and after researching deeper found most use copper clad aluminum. I hate that stuff as I need to cut the cables and solder one end elsewhere. I have had good enough luck with the JST crimping but have another crimper on my list to order. It's ok.? You just don't want to mix the 2 mm and 2.54 mm stuff. I generally use 0.1 inch spacing because that's easy to find. The 2.0 mm(or less) JST I use where someone else used it.
I wanted to design a total SMT pcb and I could solder the power and ground wires to a pad. Then I thought about adding a JST header and use a plug for power and ground. That works.
??????????? Except I don't have any SMT headers in JST XH and although they are available, they come in a 3 circuit style and a 4 and a 5. I really only wanted a 2 circuit version but I have that in a through hole and its also a 90 degree version to save some space on the enclosure height,.
Ok, here's a trick.? I use 5.0 volts as a bulk supply and on each board, typically regulate it to 3.3 volts (this is mostly microprocessor stuff and 3.3 volt modules.? I use 3 pin power connectors (in red) with the inner pin being ground and the outer two pins being +5.? You can't reverse polarity the board except by getting the connector one pin off.
I use through hole connectors.? It doesn't do anything bad except to eat up a little board space.? Remember that on a 90 degree connector, you trade off width for height, and it can make a difference.
Where possible, I make some of the connections symmetric like that.? It costs extra pins, but saves some problems.
Problem is, the JST parts are all through hole. So now for my question ( I may have a clue but will ask anyhow to verify ), what is the best method on the board design to use through hole and SMT at the same time? I just put them in and let the router do its work.? For your design, you might want to have separate power pins if the supplies are different, say that if you need +5 for the top circuit and +12 for the lower one, have a power connector with separate pins for the two supplies.? That keeps the power supplies from being mixed.
??????????? I guess I was worried about the power feeding the top side while being soldered to the bottom side. I figured I had to have a jumper from the bottom back to the top but now that I think of it, the holes would be plated thru holes...
The holes are plated through holes.? Using EAGLE, for instance, you route on the top layer, then change to the bottom layer, you'll see the trace turn blue and a via put in at the last place the trace stopped.? Continue to route on the bottom of the board, and change layers again to get back to the top layer. Since you don't mount boards directly on a conductive metal plate, it shouldn't matter if there is live power on the other side of the board.? That would be normal for any board.
Using the example where you have absolutely no connections between board sides, if you had a single power connector, the top and bottom grounds and power (if the same voltage) would be connected at the through holes on the connector.
Will I still be able to do my planned 2 different circuits on either side of the board? How should I handle the power header? Use it to supply both sides of the board with one header or use 2 headers for power/GND and separate the copper with islands?
?Given a common ground for both circuits (which works), you're running separate supplies from separate pins, so just one connector and wire it appropriately depending on which circuit you're doing.? You can use unused parts of the other side as jumpers.? If you don't want to do that, you can use 0 ohm resistors (1206 works best just because of the size). it's easier than running wire jumpers.
So yes, one power/signal connector can do the job if you think that the inputs/outputs don't make for too large a connector
If you have a lot of inputs and outputs, there's two ways to do this:
one is to have a separate power connector (and have separate pins for each supply rather than one "power" pin), and then separate connectors for each circuit.? I'd use different size connectors to avoid misconnections.
two is to have power and signals on one connector (perhaps few pins for signals) not sharing any pins except ground and identical power supply voltages.
??????????? I didn't even know they made "0" ohm resistors. But I am starting to understand it now. I guess I will start to design it and then in the software things will become obvious.
I think so.? EAGLE's autorouter makes assumptions with their standard setups that are good for having the boards manufactured, but not good for things like toner transfer boards (10/10; 10 mil traces and 10 mil spacing between conductors are workable).? If you're making boards, you need one setup.? If you're having boards made, then use their recommended setups and you're fine.
This is likely true with any other layout program.? Your PCB layout program will automatically (or should) insert a via when you change layers.
Harvey
Thanks,
Dave
Harvey
Thanks,
Dave
|
Ok, thanks for the info. I was just making sure a device doesn't exist like a special switch that could do the same. But I can make it work if I need to. Using single wires to plug power and ground works the easiest but my supplier has 0 JST single plug housings as they are on back order. No rush, I will possibly just back order some for future reference.
Dave
toggle quoted message
Show quoted text
On 11/13/2020 6:14 PM, Harvey White wrote: If the connector is keyed, and you really can't plug it in backwards, then you don't need symmetric pins.? Some connectors can be forced in backwards.
There are keys that fit into the connector in place of a socket. The mating pin needs to be removed.? I might try to 3D print some of them, but the best solution might be to go to a hobby shop and get some very thin plastic that could fit into the connector from the back to block the pin being inserted.
I've tried finding them, but they seem to be rather expensive, where they are available.
So for connectors where the body is not keyed, you need to key the pins if it's important.? Another method would be to put power and ground in such locations that plugging the connector in backwards doesn't connect nasty signals (like outputs to outputs), power to ground, etc.? This takes some careful work and may not always be possible.
The symmetric method is workable, and you may end up thinking of 3D printing your own shrouds for the on board pins to keep the plug from being inserted off by a pin (or just key it).
Harvey
On 11/13/2020 6:18 PM, Dave wrote:
Thanks Harvey. It all makes perfect sense now that I remembered the VIA. One bonus round question. What if you wanted to reverse the polarity and you had a connector ( 2 pin ) that was "keyed" so you couldn't just unplug and re-plug it in the opposite way? Like with a JST XH series. I know with a standard 0.1 header pins that wouldn't be a problem but are there any tricks to make that happen? Just curious because us noobs ask the strangest questions and sometimes they are good ones.
Thanks,
Dave
On 11/13/2020 4:46 PM, Harvey White wrote:
yet more replies.....
On 11/13/2020 3:42 PM, Dave wrote:
Interleaved some more.
On 11/13/2020 12:53 PM, Harvey White wrote:
Interleaved.
On 11/13/2020 1:11 PM, Dave wrote:
Harvey,
? I have a related question here after spending some time researching. I already have a bunch of JST XH connectors and plugs, and pins and the crimper. Instead of JST, I use 0.1 inch spacing connectors.? The female/female jumpers can be tweaked to remove the individual shrouds, and can be reinserted in strip connectors to make some decent cables.? JST will work fine, but I've found them tricky to use.? I'd just as soon look for premade cables. Your luck with the crimper (I hope) will be better than mine. ??????????? The .1 inch (2.54mm) spacing should work ok with the JST 2.5mm spacing, at least for short length stuff. SO I should be good there. I did look at premade cables but noticed nobody bragging about 100% copper and after researching deeper found most use copper clad aluminum. I hate that stuff as I need to cut the cables and solder one end elsewhere. I have had good enough luck with the JST crimping but have another crimper on my list to order. It's ok.? You just don't want to mix the 2 mm and 2.54 mm stuff. I generally use 0.1 inch spacing because that's easy to find. The 2.0 mm(or less) JST I use where someone else used it.
I wanted to design a total SMT pcb and I could solder the power and ground wires to a pad. Then I thought about adding a JST header and use a plug for power and ground. That works.
??????????? Except I don't have any SMT headers in JST XH and although they are available, they come in a 3 circuit style and a 4 and a 5. I really only wanted a 2 circuit version but I have that in a through hole and its also a 90 degree version to save some space on the enclosure height,.
Ok, here's a trick.? I use 5.0 volts as a bulk supply and on each board, typically regulate it to 3.3 volts (this is mostly microprocessor stuff and 3.3 volt modules.? I use 3 pin power connectors (in red) with the inner pin being ground and the outer two pins being +5.? You can't reverse polarity the board except by getting the connector one pin off.
I use through hole connectors.? It doesn't do anything bad except to eat up a little board space.? Remember that on a 90 degree connector, you trade off width for height, and it can make a difference.
Where possible, I make some of the connections symmetric like that.? It costs extra pins, but saves some problems.
Problem is, the JST parts are all through hole. So now for my question ( I may have a clue but will ask anyhow to verify ), what is the best method on the board design to use through hole and SMT at the same time? I just put them in and let the router do its work.? For your design, you might want to have separate power pins if the supplies are different, say that if you need +5 for the top circuit and +12 for the lower one, have a power connector with separate pins for the two supplies.? That keeps the power supplies from being mixed.
??????????? I guess I was worried about the power feeding the top side while being soldered to the bottom side. I figured I had to have a jumper from the bottom back to the top but now that I think of it, the holes would be plated thru holes...
The holes are plated through holes.? Using EAGLE, for instance, you route on the top layer, then change to the bottom layer, you'll see the trace turn blue and a via put in at the last place the trace stopped.? Continue to route on the bottom of the board, and change layers again to get back to the top layer. Since you don't mount boards directly on a conductive metal plate, it shouldn't matter if there is live power on the other side of the board.? That would be normal for any board.
Using the example where you have absolutely no connections between board sides, if you had a single power connector, the top and bottom grounds and power (if the same voltage) would be connected at the through holes on the connector.
Will I still be able to do my planned 2 different circuits on either side of the board? How should I handle the power header? Use it to supply both sides of the board with one header or use 2 headers for power/GND and separate the copper with islands?
?Given a common ground for both circuits (which works), you're running separate supplies from separate pins, so just one connector and wire it appropriately depending on which circuit you're doing.? You can use unused parts of the other side as jumpers.? If you don't want to do that, you can use 0 ohm resistors (1206 works best just because of the size). it's easier than running wire jumpers.
So yes, one power/signal connector can do the job if you think that the inputs/outputs don't make for too large a connector
If you have a lot of inputs and outputs, there's two ways to do this:
one is to have a separate power connector (and have separate pins for each supply rather than one "power" pin), and then separate connectors for each circuit.? I'd use different size connectors to avoid misconnections.
two is to have power and signals on one connector (perhaps few pins for signals) not sharing any pins except ground and identical power supply voltages.
??????????? I didn't even know they made "0" ohm resistors. But I am starting to understand it now. I guess I will start to design it and then in the software things will become obvious.
I think so.? EAGLE's autorouter makes assumptions with their standard setups that are good for having the boards manufactured, but not good for things like toner transfer boards (10/10; 10 mil traces and 10 mil spacing between conductors are workable).? If you're making boards, you need one setup.? If you're having boards made, then use their recommended setups and you're fine.
This is likely true with any other layout program.? Your PCB layout program will automatically (or should) insert a via when you change layers.
Harvey
Thanks,
Dave
Harvey
Thanks,
Dave
|
Try amazon and connector assortments.? You'd be surprised how many there are, and how many don't have what you want.? I always (if possible) go for amazon shipping because the "sold by amazon" has a certain guarantee, and the shipping by amazon (free, of course) is annoying as #$%#$%##!!! but is.... free......
If it's not like that, it's mailed from China, you can tell by the delivery dates.
Amazon seems to be good at returns.? I got one thing that was a bunch of stepup converters in a box, no padding.? Some were broken, so back it went.? I got an "amazon renewed" hot air desoldering system with a clearly burned out heating element. Back it went.? No problems in either case.
Harvey
toggle quoted message
Show quoted text
On 11/13/2020 7:23 PM, Dave wrote: Ok, thanks for the info. I was just making sure a device doesn't exist like a special switch that could do the same. But I can make it work if I need to. Using single wires to plug power and ground works the easiest but my supplier has 0 JST single plug housings as they are on back order. No rush, I will possibly just back order some for future reference.
Dave
On 11/13/2020 6:14 PM, Harvey White wrote:
If the connector is keyed, and you really can't plug it in backwards, then you don't need symmetric pins. Some connectors can be forced in backwards.
There are keys that fit into the connector in place of a socket. The mating pin needs to be removed.? I might try to 3D print some of them, but the best solution might be to go to a hobby shop and get some very thin plastic that could fit into the connector from the back to block the pin being inserted.
I've tried finding them, but they seem to be rather expensive, where they are available.
So for connectors where the body is not keyed, you need to key the pins if it's important.? Another method would be to put power and ground in such locations that plugging the connector in backwards doesn't connect nasty signals (like outputs to outputs), power to ground, etc.? This takes some careful work and may not always be possible.
The symmetric method is workable, and you may end up thinking of 3D printing your own shrouds for the on board pins to keep the plug from being inserted off by a pin (or just key it).
Harvey
On 11/13/2020 6:18 PM, Dave wrote:
Thanks Harvey. It all makes perfect sense now that I remembered the VIA. One bonus round question. What if you wanted to reverse the polarity and you had a connector ( 2 pin ) that was "keyed" so you couldn't just unplug and re-plug it in the opposite way? Like with a JST XH series. I know with a standard 0.1 header pins that wouldn't be a problem but are there any tricks to make that happen? Just curious because us noobs ask the strangest questions and sometimes they are good ones.
Thanks,
Dave
On 11/13/2020 4:46 PM, Harvey White wrote:
yet more replies.....
On 11/13/2020 3:42 PM, Dave wrote:
Interleaved some more.
On 11/13/2020 12:53 PM, Harvey White wrote:
Interleaved.
On 11/13/2020 1:11 PM, Dave wrote:
Harvey,
? I have a related question here after spending some time researching. I already have a bunch of JST XH connectors and plugs, and pins and the crimper. Instead of JST, I use 0.1 inch spacing connectors.? The female/female jumpers can be tweaked to remove the individual shrouds, and can be reinserted in strip connectors to make some decent cables.? JST will work fine, but I've found them tricky to use.? I'd just as soon look for premade cables. Your luck with the crimper (I hope) will be better than mine. ??????????? The .1 inch (2.54mm) spacing should work ok with the JST 2.5mm spacing, at least for short length stuff. SO I should be good there. I did look at premade cables but noticed nobody bragging about 100% copper and after researching deeper found most use copper clad aluminum. I hate that stuff as I need to cut the cables and solder one end elsewhere. I have had good enough luck with the JST crimping but have another crimper on my list to order. It's ok.? You just don't want to mix the 2 mm and 2.54 mm stuff. I generally use 0.1 inch spacing because that's easy to find. The 2.0 mm(or less) JST I use where someone else used it.
I wanted to design a total SMT pcb and I could solder the power and ground wires to a pad. Then I thought about adding a JST header and use a plug for power and ground. That works.
??????????? Except I don't have any SMT headers in JST XH and although they are available, they come in a 3 circuit style and a 4 and a 5. I really only wanted a 2 circuit version but I have that in a through hole and its also a 90 degree version to save some space on the enclosure height,.
Ok, here's a trick.? I use 5.0 volts as a bulk supply and on each board, typically regulate it to 3.3 volts (this is mostly microprocessor stuff and 3.3 volt modules.? I use 3 pin power connectors (in red) with the inner pin being ground and the outer two pins being +5.? You can't reverse polarity the board except by getting the connector one pin off.
I use through hole connectors.? It doesn't do anything bad except to eat up a little board space.? Remember that on a 90 degree connector, you trade off width for height, and it can make a difference.
Where possible, I make some of the connections symmetric like that.? It costs extra pins, but saves some problems.
Problem is, the JST parts are all through hole. So now for my question ( I may have a clue but will ask anyhow to verify ), what is the best method on the board design to use through hole and SMT at the same time? I just put them in and let the router do its work.? For your design, you might want to have separate power pins if the supplies are different, say that if you need +5 for the top circuit and +12 for the lower one, have a power connector with separate pins for the two supplies.? That keeps the power supplies from being mixed.
??????????? I guess I was worried about the power feeding the top side while being soldered to the bottom side. I figured I had to have a jumper from the bottom back to the top but now that I think of it, the holes would be plated thru holes...
The holes are plated through holes.? Using EAGLE, for instance, you route on the top layer, then change to the bottom layer, you'll see the trace turn blue and a via put in at the last place the trace stopped.? Continue to route on the bottom of the board, and change layers again to get back to the top layer. Since you don't mount boards directly on a conductive metal plate, it shouldn't matter if there is live power on the other side of the board.? That would be normal for any board.
Using the example where you have absolutely no connections between board sides, if you had a single power connector, the top and bottom grounds and power (if the same voltage) would be connected at the through holes on the connector.
Will I still be able to do my planned 2 different circuits on either side of the board? How should I handle the power header? Use it to supply both sides of the board with one header or use 2 headers for power/GND and separate the copper with islands?
?Given a common ground for both circuits (which works), you're running separate supplies from separate pins, so just one connector and wire it appropriately depending on which circuit you're doing.? You can use unused parts of the other side as jumpers.? If you don't want to do that, you can use 0 ohm resistors (1206 works best just because of the size). it's easier than running wire jumpers.
So yes, one power/signal connector can do the job if you think that the inputs/outputs don't make for too large a connector
If you have a lot of inputs and outputs, there's two ways to do this:
one is to have a separate power connector (and have separate pins for each supply rather than one "power" pin), and then separate connectors for each circuit. I'd use different size connectors to avoid misconnections.
two is to have power and signals on one connector (perhaps few pins for signals) not sharing any pins except ground and identical power supply voltages.
??????????? I didn't even know they made "0" ohm resistors. But I am starting to understand it now. I guess I will start to design it and then in the software things will become obvious.
I think so.? EAGLE's autorouter makes assumptions with their standard setups that are good for having the boards manufactured, but not good for things like toner transfer boards (10/10; 10 mil traces and 10 mil spacing between conductors are workable).? If you're making boards, you need one setup.? If you're having boards made, then use their recommended setups and you're fine.
This is likely true with any other layout program.? Your PCB layout program will automatically (or should) insert a via when you change layers.
Harvey
Thanks,
Dave
Harvey
Thanks,
Dave
|
One trick is if you have a three pin connector is to use the center pin for
positive and the two outside pins connected to ground. Then polarity does
not matter.
Another common thing on multipin strip connectors is to remove a male pin
and insert a dummy plug in the matching female location. If reversed, it
will not plug in.
That reminds me. A very long time ago we were manufacturing a product with
a 12 pin in line connector with a missing pin. It turns out that a square
toothpick fit perfectly as a plug for the female connector: Just push it
all the way in and cut it off flush.
We had an angry customer calling about our terrible quality: He said there
was even a piece of wood stuck in the connector and it took him a long time
to remove it. Then even worse he said, when he finally plugged it in there
was smoke coming from the PCB and it did not work. Of course he had plugged
it in backwards.
Bertho
|
Harvey,
? I buy from Amazon a lot but I also price check them a lot too. I have had pretty good luck with them and if something goes awry, they fix it no problem.
Dave
toggle quoted message
Show quoted text
On 11/13/2020 7:04 PM, Harvey White wrote: Try amazon and connector assortments.? You'd be surprised how many there are, and how many don't have what you want.? I always (if possible) go for amazon shipping because the "sold by amazon" has a certain guarantee, and the shipping by amazon (free, of course) is annoying as #$%#$%##!!! but is.... free......
If it's not like that, it's mailed from China, you can tell by the delivery dates.
Amazon seems to be good at returns.? I got one thing that was a bunch of stepup converters in a box, no padding.? Some were broken, so back it went.? I got an "amazon renewed" hot air desoldering system with a clearly burned out heating element. Back it went.? No problems in either case.
Harvey
|
Bertho,
? Funny story. :) But in my case I was hoping and also using my JST connectors, there was a way to reverse polarity. Of course putting together the project correct would be ideal, but in the past not all LED's are properly configured as far as polarity. Once the project is soldered up I have (only once or twice) had the polarity backwards. The easy fix would be to unplug a connector and re-plug it in opposite for the power feed. So far everything I have done has been soldered so it makes it a little harder to fix but not really that hard. But when I switch to plugs using JST connectors I was just curious if there was a trick for future use just in case. Like a few jumpers that could be swapped around. In the end I will just pay attention and color code with wire colors etc.
Dave
toggle quoted message
Show quoted text
On 11/13/2020 10:35 PM, Bertho wrote: One trick is if you have a three pin connector is to use the center pin for
positive and the two outside pins connected to ground. Then polarity does
not matter.
Another common thing on multipin strip connectors is to remove a male pin
and insert a dummy plug in the matching female location. If reversed, it
will not plug in.
That reminds me. A very long time ago we were manufacturing a product with
a 12 pin in line connector with a missing pin. It turns out that a square
toothpick fit perfectly as a plug for the female connector: Just push it
all the way in and cut it off flush.
We had an angry customer calling about our terrible quality: He said there
was even a piece of wood stuck in the connector and it took him a long time
to remove it. Then even worse he said, when he finally plugged it in there
was smoke coming from the PCB and it did not work. Of course he had plugged
it in backwards.
Bertho
|
I would not use reversing a connector for the fix of an LED installed backwards.? I'd be very tempted to check them first. Most of what I use has an index mark on it indicating the cathode.
If you have a board where you can plug in the power backwards, then you have to think about how to plug in the power every time. Thinking is a quantity noticeably absent as the hour for late night debugging goes past 12 midnight.
One group of college students was in a robot competition, powering their project with a high power lithium ion battery. They didn't key the connector (for whatever reason), nor did they install any sort of polarity protection, not even a fuse and a reverse biased diode.
Three hours from home on a Sunday and before the competition, they plugged in the battery backwards and blew every power module in the robot.? Even an early morning run for spare parts made no difference to the outcome.
And that is why George always wear hat when visiting Tooki-Tooki bird friends.
One of the tweezer probes with banana plugs and one of the parts checkers (transistor/diode/LED/capacitor) can be used to identify an LED before you put it in.? Since they run off 5 volts (regulated from a 9 volt battery), you have enough voltage for blue and white LEDS.? You can also get them with a PC board pattern that allows directly putting SMT chips on the tester.
Harvey
toggle quoted message
Show quoted text
On 11/14/2020 11:34 AM, Dave wrote: Bertho,
? Funny story. :) But in my case I was hoping and also using my JST connectors, there was a way to reverse polarity. Of course putting together the project correct would be ideal, but in the past not all LED's are properly configured as far as polarity. Once the project is soldered up I have (only once or twice) had the polarity backwards. The easy fix would be to unplug a connector and re-plug it in opposite for the power feed. So far everything I have done has been soldered so it makes it a little harder to fix but not really that hard. But when I switch to plugs using JST connectors I was just curious if there was a trick for future use just in case. Like a few jumpers that could be swapped around. In the end I will just pay attention and color code with wire colors etc.
Dave
On 11/13/2020 10:35 PM, Bertho wrote:
One trick is if you have a three pin connector is to use the center pin for
positive and the two outside pins connected to ground.? Then polarity does
not matter.
Another common thing on multipin strip connectors is to remove a male pin
and insert a dummy plug in the matching female location.? If reversed, it
will not plug in.
That reminds me.? A very long time ago we were manufacturing a product with
a 12 pin in line connector with a missing pin.? It turns out that a square
toothpick fit perfectly as a plug for the female connector: Just push it
all the way in and cut it off flush.
We had an angry customer calling about our terrible quality:? He said there
was even a piece of wood stuck in the connector and it took him a long time
to remove it.? Then even worse he said, when he finally plugged it in there
was smoke coming from the PCB and it did not work.? Of course he had plugged
it in backwards.
Bertho
|
Harvey,
? In my case the circuit is so simple no harm can be done but I do get your point. From the batteries to a jack with a female plug. Inside the box the jack is hardwired to the pcb. The only time it has to be swapped is on assembly and is covered after that. What got me in the beginning is that the IR led's I use have the anode and cathode reversed so the flat on the LED is not the cathode or the negative like 99% of the other led's out there. I always test them on the breadboard but being my mind always thinks the negative is the short lead, I have solder the red and black wires onto the led incorrectly. Then as assembly continues it ends up backwards. It is not a big deal though as now I have ordered some Dupont female pins and housings to solve that issue if it ever comes up again. For the most part I likely won't ever make the mistake again but was curious if a polarity switcher was possible a device because they seem to make everything.
Thanks,
Dave
toggle quoted message
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On 11/14/2020 11:59 AM, Harvey White wrote: I would not use reversing a connector for the fix of an LED installed backwards.? I'd be very tempted to check them first. Most of what I use has an index mark on it indicating the cathode.
If you have a board where you can plug in the power backwards, then you have to think about how to plug in the power every time. Thinking is a quantity noticeably absent as the hour for late night debugging goes past 12 midnight.
One group of college students was in a robot competition, powering their project with a high power lithium ion battery. They didn't key the connector (for whatever reason), nor did they install any sort of polarity protection, not even a fuse and a reverse biased diode.
Three hours from home on a Sunday and before the competition, they plugged in the battery backwards and blew every power module in the robot.? Even an early morning run for spare parts made no difference to the outcome.
And that is why George always wear hat when visiting Tooki-Tooki bird friends.
One of the tweezer probes with banana plugs and one of the parts checkers (transistor/diode/LED/capacitor) can be used to identify an LED before you put it in.? Since they run off 5 volts (regulated from a 9 volt battery), you have enough voltage for blue and white LEDS.? You can also get them with a PC board pattern that allows directly putting SMT chips on the tester.
Harvey
On 11/14/2020 11:34 AM, Dave wrote:
Bertho,
? Funny story. :) But in my case I was hoping and also using my JST connectors, there was a way to reverse polarity. Of course putting together the project correct would be ideal, but in the past not all LED's are properly configured as far as polarity. Once the project is soldered up I have (only once or twice) had the polarity backwards. The easy fix would be to unplug a connector and re-plug it in opposite for the power feed. So far everything I have done has been soldered so it makes it a little harder to fix but not really that hard. But when I switch to plugs using JST connectors I was just curious if there was a trick for future use just in case. Like a few jumpers that could be swapped around. In the end I will just pay attention and color code with wire colors etc.
Dave
On 11/13/2020 10:35 PM, Bertho wrote:
One trick is if you have a three pin connector is to use the center pin for
positive and the two outside pins connected to ground.? Then polarity does
not matter.
Another common thing on multipin strip connectors is to remove a male pin
and insert a dummy plug in the matching female location.? If reversed, it
will not plug in.
That reminds me.? A very long time ago we were manufacturing a product with
a 12 pin in line connector with a missing pin.? It turns out that a square
toothpick fit perfectly as a plug for the female connector: Just push it
all the way in and cut it off flush.
We had an angry customer calling about our terrible quality: He said there
was even a piece of wood stuck in the connector and it took him a long time
to remove it.? Then even worse he said, when he finally plugged it in there
was smoke coming from the PCB and it did not work.? Of course he had plugged
it in backwards.
Bertho
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Ok, just trying to encourage good habits.? You might want to consider putting a silk screen outline of the part (you draw it) on the board, or add two spdt style (middle with two ends) jumper pads hooked up to reverse the polarity if both are shorted in one position, and not reverse the polarity if both are shorted in the other position.? This, of course, goes to the diode and will allow you to use normal LEDS as well as the reversed one.? It does add an extra step, but allows more of a "just make it like the drawing" assembly, which is very frequently a good thing.
The same technique can be used to control the state of address pins, write enable pins, and the like *if* the pins can tolerate a direct connection to vcc.? If not (TTL would be an example where you'd want a 1K series resistor, old design practice here), then put in the appropriate resistors. You could also just wire pullups to the pin and use an SPST jumper to ground the pin when needed.
The jumpers look like resistor pads, but closer together. They're designed to be shorted together with a solder blob.? I'd rather use them than 0 ohm resistors because the resistors are an extra step.? You use the 0 ohm resistors if you want to run traces between the pads.? Some manufacturers use 0 ohm resistors for configuration since they use pick and place machines to put parts on the board.? Since you're doing things by hand, that's not needed.
The closest I can come to a polarity switcher is the set of jumpers above.
Harvey
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On 11/14/2020 1:18 PM, Dave wrote: Harvey,
? In my case the circuit is so simple no harm can be done but I do get your point. From the batteries to a jack with a female plug. Inside the box the jack is hardwired to the pcb. The only time it has to be swapped is on assembly and is covered after that. What got me in the beginning is that the IR led's I use have the anode and cathode reversed so the flat on the LED is not the cathode or the negative like 99% of the other led's out there. I always test them on the breadboard but being my mind always thinks the negative is the short lead, I have solder the red and black wires onto the led incorrectly. Then as assembly continues it ends up backwards. It is not a big deal though as now I have ordered some Dupont female pins and housings to solve that issue if it ever comes up again. For the most part I likely won't ever make the mistake again but was curious if a polarity switcher was possible a device because they seem to make everything.
Thanks,
Dave
On 11/14/2020 11:59 AM, Harvey White wrote:
I would not use reversing a connector for the fix of an LED installed backwards.? I'd be very tempted to check them first. Most of what I use has an index mark on it indicating the cathode.
If you have a board where you can plug in the power backwards, then you have to think about how to plug in the power every time. Thinking is a quantity noticeably absent as the hour for late night debugging goes past 12 midnight.
One group of college students was in a robot competition, powering their project with a high power lithium ion battery. They didn't key the connector (for whatever reason), nor did they install any sort of polarity protection, not even a fuse and a reverse biased diode.
Three hours from home on a Sunday and before the competition, they plugged in the battery backwards and blew every power module in the robot.? Even an early morning run for spare parts made no difference to the outcome.
And that is why George always wear hat when visiting Tooki-Tooki bird friends.
One of the tweezer probes with banana plugs and one of the parts checkers (transistor/diode/LED/capacitor) can be used to identify an LED before you put it in.? Since they run off 5 volts (regulated from a 9 volt battery), you have enough voltage for blue and white LEDS.? You can also get them with a PC board pattern that allows directly putting SMT chips on the tester.
Harvey
On 11/14/2020 11:34 AM, Dave wrote:
Bertho,
? Funny story. :) But in my case I was hoping and also using my JST connectors, there was a way to reverse polarity. Of course putting together the project correct would be ideal, but in the past not all LED's are properly configured as far as polarity. Once the project is soldered up I have (only once or twice) had the polarity backwards. The easy fix would be to unplug a connector and re-plug it in opposite for the power feed. So far everything I have done has been soldered so it makes it a little harder to fix but not really that hard. But when I switch to plugs using JST connectors I was just curious if there was a trick for future use just in case. Like a few jumpers that could be swapped around. In the end I will just pay attention and color code with wire colors etc.
Dave
On 11/13/2020 10:35 PM, Bertho wrote:
One trick is if you have a three pin connector is to use the center pin for
positive and the two outside pins connected to ground.? Then polarity does
not matter.
Another common thing on multipin strip connectors is to remove a male pin
and insert a dummy plug in the matching female location.? If reversed, it
will not plug in.
That reminds me.? A very long time ago we were manufacturing a product with
a 12 pin in line connector with a missing pin.? It turns out that a square
toothpick fit perfectly as a plug for the female connector: Just push it
all the way in and cut it off flush.
We had an angry customer calling about our terrible quality: He said there
was even a piece of wood stuck in the connector and it took him a long time
to remove it.? Then even worse he said, when he finally plugged it in there
was smoke coming from the PCB and it did not work.? Of course he had plugged
it in backwards.
Bertho
|
Bertho