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


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

-----Original Message-----
From: [email protected] <[email protected]> On Behalf
Of Dave
Sent: Sunday, 15 November 2020 6:49 AM
To: [email protected]
Subject: Re: [homebrewpcbs] Circuits on 2 sides

I was thinking something like that with the multiple jumpers or those 2
position switch banks but that would be overkill (the dip switches). I

wasn't sure how to draw it up. I like good habits though. :) I like the

you presented as I thought it could be done with simple jumpers and the
solder idea makes it even better. Of course wiring it correct in the first

makes it best. I did a little reading on 0 ohm resistors yesterday. Always
something to learn. It never ends. That is the fun part though.

Thanks,

Dave

On 11/14/2020 1:28 PM, Harvey White wrote:

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


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

The classic polarity reversing is usually a motor hooked up to a DPDT
switch, like this:

Replace the switch with a 2x3 header and a couple of jumpers, and you're
good to go.

Tony

-----Original Message-----
From: [email protected] <[email protected]> On Behalf
Of Dave
Sent: Sunday, 15 November 2020 6:49 AM
To: [email protected]
Subject: Re: [homebrewpcbs] Circuits on 2 sides

I was thinking something like that with the multiple jumpers or those 2
position switch banks but that would be overkill (the dip switches). I

just

wasn't sure how to draw it up. I like good habits though. :) I like the

idea that

you presented as I thought it could be done with simple jumpers and the
solder idea makes it even better. Of course wiring it correct in the first

place

makes it best. I did a little reading on 0 ohm resistors yesterday. Always
something to learn. It never ends. That is the fun part though.

Thanks,

Dave

On 11/14/2020 1:28 PM, Harvey White wrote:

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


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

I would still strongly recommend a polarised connector. Somewhere down
the road, someone (it might even be you) will have to look at your PCB;
you wouldn't want them to think, "What was he thinking?" Make it easy
for that person.

I spent most of my life doing programming, rather than
electrical/electronic stuff, though I did plenty of that too, and
encouraged my programmers to remember: you aren't writing code for the
CPU, or the compiler; you are writing code for some poor SOB three years
after you've gone away, who has to figure out why you did what you did.
Any half-decent programmer can read the code and know what it does; what
they need to know is WHY it does what it does! Make it easy for them.

My opinion,
Donald.
--
*Plain Text* email -- it's an accessibility issue
() no proprietary attachments; no html mail
/\ <>

On 2020-11-14 1:18 p.m., 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

Dave,
The easy, foolproof way is to add a diode bridge and it does not matter how
it is plugged in.
The drawback is that you have two extra diode voltage drops.
Bertho

Dave,
The easy, foolproof way is to add a diode bridge and it does not matter how
it is plugged in.
The drawback is that you have two extra diode voltage drops.
Bertho

That takes care of the power supply polarity to the board (you might want to investigate a P Channel FET for a power protection device, it works for reverse polarity as long as you don't exceed a negative input greater than the gate/source rating).

It doesn't help the LED on the board at all.? I'm assuming more on the board than just a resistor and LED, though.

Harvey


On 11/14/2020 7:08 PM, Bertho wrote:

Dave,
The easy, foolproof way is to add a diode bridge and it does not matter how
it is plugged in.
The drawback is that you have two extra diode voltage drops.
Bertho

That takes care of the power supply polarity to the board (you might want to investigate a P Channel FET for a power protection device, it works for reverse polarity as long as you don't exceed a negative input greater than the gate/source rating).

It doesn't help the LED on the board at all.? I'm assuming more on the board than just a resistor and LED, though.

Harvey


On 11/14/2020 7:08 PM, Bertho wrote:

Dave,
The easy, foolproof way is to add a diode bridge and it does not matter how
it is plugged in.
The drawback is that you have two extra diode voltage drops.

-----Original Message-----
From: [email protected] <[email protected]> On Behalf
Of Dave
Sent: Monday, 16 November 2020 2:54 AM
To: [email protected]
Subject: Re: [homebrewpcbs] Circuits on 2 sides

I thought a diode bridge or bridge rectifier was to convert AC to DC. So

diode bridge work on DC?

Thanks,

Dave

On 11/14/2020 6:08 PM, Bertho wrote:

Dave,
The easy, foolproof way is to add a diode bridge and it does not
matter how it is plugged in.
The drawback is that you have two extra diode voltage drops.
Bertho

Helps if you think of AC as DC that keeps getting it's polarity reversed.

So yes, a diode bridge will let DC through, but one polarity will get
flipped.

Tony

-----Original Message-----
From: [email protected] <[email protected]> On Behalf
Of Dave
Sent: Monday, 16 November 2020 2:54 AM
To: [email protected]
Subject: Re: [homebrewpcbs] Circuits on 2 sides

I thought a diode bridge or bridge rectifier was to convert AC to DC. So

does a

diode bridge work on DC?

Thanks,

Dave

On 11/14/2020 6:08 PM, Bertho wrote:

Dave,
The easy, foolproof way is to add a diode bridge and it does not
matter how it is plugged in.
The drawback is that you have two extra diode voltage drops.
Bertho

People call it polarity independent powering?

On Sun, 15 Nov 2020, 9:24 pm Dave, <theschemer@...> wrote:

I thought a diode bridge or bridge rectifier was to convert AC to DC. So
does a diode bridge work on DC?

Thanks,

Dave

On 11/14/2020 6:08 PM, Bertho wrote:
> Dave,
> The easy, foolproof way is to add a diode bridge and it does not matter how
> it is plugged in.
> The drawback is that you have two extra diode voltage drops.
> Bertho
>

I thought a diode bridge or bridge rectifier was to convert AC to DC. So does a diode bridge work on DC?

Thanks,

Dave

On 11/14/2020 6:08 PM, Bertho wrote:

Dave,
The easy, foolproof way is to add a diode bridge and it does not matter how
it is plugged in.
The drawback is that you have two extra diode voltage drops.
Bertho

That sounds like it needs me to go do some research on that one. :) I
use a PTC fues for protection on the USB powered version but my other
boards use battery power from 2.4 to whatever voltage but usually 3v
max. And like I asked Bertho, does a diode bridge even work with DC?

Thanks,

Dave

On 11/14/2020 7:36 PM, Harvey White wrote:

That takes care of the power supply polarity to the board (you might
want to investigate a P Channel FET for a power protection device, it
works for reverse polarity as long as you don't exceed a negative
input greater than the gate/source rating).

It doesn't help the LED on the board at all.? I'm assuming more on the
board than just a resistor and LED, though.

Harvey


On 11/14/2020 7:08 PM, Bertho wrote:

Dave,
The easy, foolproof way is to add a diode bridge and it does not
matter how
it is plugged in.
The drawback is that you have two extra diode voltage drops.
Bertho

That sounds like it needs me to go do some research on that one. :) I use a PTC fues for protection on the USB powered version but my other boards use battery power from 2.4 to whatever voltage but usually 3v max. And like I asked Bertho, does a diode bridge even work with DC?

Thanks,

Dave

On 11/14/2020 7:36 PM, Harvey White wrote:

That takes care of the power supply polarity to the board (you might want to investigate a P Channel FET for a power protection device, it works for reverse polarity as long as you don't exceed a negative input greater than the gate/source rating).

It doesn't help the LED on the board at all.? I'm assuming more on the board than just a resistor and LED, though.

Harvey


On 11/14/2020 7:08 PM, Bertho wrote:

Dave,
The easy, foolproof way is to add a diode bridge and it does not matter how
it is plugged in.
The drawback is that you have two extra diode voltage drops.
Bertho

Have a look at


There are many sites with similar/identical circuits for reverse voltage
protection.

Donald.
--
*Plain Text* email -- it's an accessibility issue
() no proprietary attachments; no html mail
/\ <>

On 2020-11-15 10:57 a.m., Dave wrote:

That sounds like it needs me to go do some research on that one. :) I
use a PTC fues for protection on the USB powered version but my other
boards use battery power from 2.4 to whatever voltage but usually 3v
max. And like I asked Bertho, does a diode bridge even work with DC?

Thanks,

Dave

On 11/14/2020 7:36 PM, Harvey White wrote:

That takes care of the power supply polarity to the board (you might
want to investigate a P Channel FET for a power protection device, it
works for reverse polarity as long as you don't exceed a negative
input greater than the gate/source rating).

It doesn't help the LED on the board at all.? I'm assuming more on the
board than just a resistor and LED, though.

Harvey


On 11/14/2020 7:08 PM, Bertho wrote:

Dave,
The easy, foolproof way is to add a diode bridge and it does not
matter how
it is plugged in.
The drawback is that you have two extra diode voltage drops.
Bertho