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Reverse polarity diode circuit
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Jeff Davis
What a wonderful addition to the shack and field. Thank you.
However, please note: The diode from the plus terminal to ground is a great idea for all of us, but there is a problem if the wrong polarity is connected as shown in the diagram. If reverse polarity is applied, and the diode conducts to ground letting out the smoke, the diode is now open but the reversed voltage is still across the transceiver ready to do major damage. What is needed is the proper type and size fuse in series with the incoming power supply before the diode or plus terminal. Now, when the diode conducts, the fuse blows disconnecting the reverse connected supply from the transceiver. The diode should still be ok. ve3coj... Jeff |
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Agreed! One should always fuse anyway. My favorite is the Polyfuse. Self-resetting, cheap, small, and easy to mount. Never be at loss for a replacement. Used them for years. Never lost one, never lost equipment. When they trip, just wait a few moments (just long enough to realize what happened, a quick dope-slap to the forehead, fix the problem and you are ready to roll!) 73, Don, ND6T
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Yup, a Polyfuse works great.
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Can add a resistor and red LED across it as an idiot light so you know when to ?execute the dope-slap. (Can also do that for a fuse) Though Farhan is looking for stuff that's easy to scrounge, doubt a Polyfuse will make it into the next rev. A small diode for both reverse protection and overcurrent protection on the main rig might be the best bet. Jerry, KE7ER On Sun, Dec 10, 2017 at 11:16 am, Don Cantrell wrote:
My favorite is the Polyfuse. |
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Jack Purdum
All: The good news: I just ordered a mega-munch of 3A, 30V polyfuses that I'd be happy to share for $1, including domestic shipping. The bad news: They're coming from China, so will likely be several weeks. I'll make a post here after they've arrived. Jack, W8TEE From: Jerry Gaffke via Groups.Io <jgaffke@...> To: [email protected] Sent: Sunday, December 10, 2017 2:24 PM Subject: Re: [BITX20] Reverse polarity diode circuit Yup, a Polyfuse works great. Can add a resistor and red LED across it as an idiot light so you know when to ?execute the dope-slap. (Can also do that for a fuse) Though Farhan is looking for stuff that's easy to scrounge, doubt a Polyfuse will make it into the next rev. A small diode for both reverse protection and overcurrent protection on the main rig might be the best bet. Jerry, KE7ER On Sun, Dec 10, 2017 at 11:16 am, Don Cantrell wrote: My favorite is the Polyfuse. |
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Vince Vielhaber
The better news, you can get them all day long from Tayda for 16 cents each. But they only have 119,418 of them in stock. To the US, shipping from Tayda is only a week for their slow boat shipping. Tayda's minimum order is $5, so for another $3 and change you can get that replacement nano!
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Vince. On 12/10/2017 02:48 PM, Jack Purdum via Groups.Io wrote:
All: --
Michigan VHF Corp. |
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Jack Purdum
Yeah, I saw that after I ordered them on line. Tayda turns up 0 if you search polyfuse, which is what I searched for. Search "polyswitch" and they pop up. I always check them first as they often ship from the distribution facility in CO. The offer will still stand for anyone who doesn't need extra stuff on the order. Jack, W8TEE From: Vince Vielhaber <vev@...> To: [email protected] Sent: Sunday, December 10, 2017 10:26 PM Subject: Re: [BITX20] Reverse polarity diode circuit The better news, you can get them all day long from Tayda for 16 cents each. But they only have 119,418 of them in stock.? To the US, shipping from Tayda is only a week for their slow boat shipping. Tayda's minimum order is $5, so for another $3 and change you can get that replacement nano! Vince. On 12/10/2017 02:48 PM, Jack Purdum via Groups.Io wrote: > All: > > The good news: I just ordered a mega-munch of 3A, 30V polyfuses that I'd > be happy to share for $1, including domestic shipping. > The bad news: They're coming from China, so will likely be several > weeks. I'll make a post here after they've arrived. > > Jack, W8TEE > > > ------------------------------------------------------------------------ > *From:* Jerry Gaffke via Groups.Io <jgaffke=[email protected]> > *To:* [email protected] > *Sent:* Sunday, December 10, 2017 2:24 PM > *Subject:* Re: [BITX20] Reverse polarity diode circuit > > Yup, a Polyfuse works great. > Can add a resistor and red LED across it as an idiot light so you know > when to? execute the dope-slap. > (Can also do that for a fuse) > > Though Farhan is looking for stuff that's easy to scrounge, doubt a > Polyfuse will make it into the next rev. > A small diode for both reverse protection and overcurrent protection on > the main rig might be the best bet. > > Jerry, KE7ER > > > On Sun, Dec 10, 2017 at 11:16 am, Don Cantrell wrote: > >? ? My favorite is the Polyfuse. > > > > -- ? Michigan VHF Corp.? ? ? ? ? ? ? ? ? ? ? ? ? ? ? |
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In some Yaesu rigs of the 80s the power was switched on by a POLARISED relay. It will not latch if the
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polarity is reverse. This is a possible no voltage loss solution! A diode can be used in series with a regular relay too. Raj At 11/12/2017, you wrote:
The better news, you can get them all day long from Tayda for 16 cents each. But they only have 119,418 of them in stock. To the US, shipping from Tayda is only a week for their slow boat shipping. Tayda's minimum order is $5, so for another $3 and change you can get that replacement nano! |
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Vince Vielhaber
It's also under circuit protection on the left side menu. BTW, the facility in Colorado just receives the completed orders from Thailand, stuffs them into envelopes, boxes, etc. and ships them out. No inventory is kept there. They used to use a facility on the East Coast.
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Vince. On 12/10/2017 11:17 PM, Jack Purdum via Groups.Io wrote:
Yeah, I saw that /after /I ordered them on line. Tayda turns up 0 if you --
Michigan VHF Corp. |
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Trent Trent
Put a alarm in the case with a diode so if the polarity is wrong it will annoy the crap out of you and everyone else near you? On 11 Dec. 2017 2:26 pm, "Vince Vielhaber" <vev@...> wrote:
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Jack Purdum
I really don't care how they do it, only that it seems to get to me faster; usually less than a week. I really get nervous about ordering from China at this time of the year as economic activity there seems to stop dead in its tracks around the Chinese New Year. I remember waiting 6 weeks last year for an order. Jack, W8TEE From: Vince Vielhaber <vev@...> To: [email protected] Sent: Sunday, December 10, 2017 11:40 PM Subject: Re: [BITX20] Reverse polarity diode circuit It's also under circuit protection on the left side menu.? BTW, the facility in Colorado just receives the completed orders from Thailand, stuffs them into envelopes, boxes, etc. and ships them out.? No inventory is kept there.? They used to use a facility on the East Coast. Vince. On 12/10/2017 11:17 PM, Jack Purdum via Groups.Io wrote: > Yeah, I saw that /after /I ordered them on line. Tayda turns up 0 if you > search polyfuse, which is what I searched for. Search "polyswitch" and > they pop up. I always check them first as they often ship from the > distribution facility in CO. The offer will still stand for anyone who > doesn't need extra stuff on the order. > > Jack, W8TEE > > > ------------------------------------------------------------------------ > *From:* Vince Vielhaber <vev@...> > *To:* [email protected] > *Sent:* Sunday, December 10, 2017 10:26 PM > *Subject:* Re: [BITX20] Reverse polarity diode circuit > > > The better news, you can get them all day long from Tayda for 16 cents > each. But they only have 119,418 of them in stock.? To the US, shipping > from Tayda is only a week for their slow boat shipping. Tayda's minimum > order is $5, so for another $3 and change you can get that replacement nano! > > Vince. > > > > On 12/10/2017 02:48 PM, Jack Purdum via Groups.Io wrote: >> All: >> >> The good news: I just ordered a mega-munch of 3A, 30V polyfuses that I'd >> be happy to share for $1, including domestic shipping. >> The bad news: They're coming from China, so will likely be several >> weeks. I'll make a post here after they've arrived. >> >> Jack, W8TEE >> >> >> ------------------------------------------------------------------------ >> *From:* Jerry Gaffke via Groups.Io <jgaffke=[email protected] > <mailto:[email protected]>> >> *To:* [email protected] <mailto:[email protected]> >> *Sent:* Sunday, December 10, 2017 2:24 PM >> *Subject:* Re: [BITX20] Reverse polarity diode circuit >> >> Yup, a Polyfuse works great. >> Can add a resistor and red LED across it as an idiot light so you know >> when to? execute the dope-slap. >> (Can also do that for a fuse) >> >> Though Farhan is looking for stuff that's easy to scrounge, doubt a >> Polyfuse will make it into the next rev. >> A small diode for both reverse protection and overcurrent protection on >> the main rig might be the best bet. >> >> Jerry, KE7ER >> >> >> On Sun, Dec 10, 2017 at 11:16 am, Don Cantrell wrote: >> >>? ? My favorite is the Polyfuse. >> >> >> >> > > -- >? Michigan VHF Corp.? <> > <> >? ? ? ? ? ? ? ? ? ? ? ? ? > <> > > > > > > -- ? Michigan VHF Corp.? ? ? ? ? ? ? ? ? ? ? ? ? ? ? |
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Vince Vielhaber
I used to be an e-cig dealer. All of my suppliers would send advanced
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warnings of the last days to order before the Chinese New Year in order to get it without the wait. All of our orders came via DHL tho, so China Post and their version of customs weren't involved. DHL handles that themselves. Vince. I really don't care how they do it, only that it seems to get to me --
Michigan VHF Corp. |
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Polyfuses are not difficult to find. Several manufacturers, even Littlefuse. I get mine from Jameco (P/N 199938) for 55 cents each (quan. 10).
Mouser and Digikey have them in surface mount, too. Not only good for reverse polarity protection (with diode), but for the occasional short circuit, too. 73, Don,ND6T |
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I also recommend a P-Mosfet in the positive line. Acts like a diode, but with much, much lower voltage drop.
Mike Y, KM5Z Dallas, Texas On Mon, Dec 11, 2017 at 08:17 am, Don Cantrell wrote:
Polyfuses are not difficult to find. Several manufacturers, even Littlefuse. I get mine from Jameco (P/N 199938) for 55 cents each (quan. 10). |
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one can make as complicated or simple a fix for this as possible. i know that several guys blew up their rigs by connecting the power in reverse. we needed a simple, cheap and easy to do fix. the diode is the fuse. it costs a few pennies. i have no fuses in my junk box, i have many diodes. if i blow one up, i can replace it with another diode. ? my target builder is actually not the kit builder, but someone who is building from her junkbox. so, i go by what a junkbox might have.? btw, talking of the chinese suppliers, i have recently bought two linear 0-30v variable voltage, variable current supplies. each for about $100. they are used to test the uBITX and BITX boards. for my own work, i have a linear power supply made out of a 5 A battery charger transformer and a hefty 78H12. it has been around for more than a decade now. - f On Tue, Dec 12, 2017 at 10:02 PM, Mike Yancey <mikeyancey@...> wrote:
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If the diode were in series with the incoming power supply, it might serve as a fuse.
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Unfortunately, that is not the case if implemented as shown here: ? with the diode placed as a reverse shunt across the power supply connector of the uBitx. If you are lucky, the supply you happen to be using will be fused with something around 3 Amps,? the 1n4007 will conduct if you reverse the power supply leads, and that will blow the fuse. And the current through the 1n4007 will never be high enough that the 1n4007's V-forward might blow an IC. If you are unlucky, your supply might have a 30A fuse, or perhaps none at all. The 1n4007 will quickly turn into a puff of smoke, and the full reversed supply will be fed to your precious *Bitx*. Here's a couple posts in an older thread that I am reasonably happy with: ? ??/g/BITX20/message/35421 ? ??/g/BITX20/message/35434 The entire thread is worth reading, there are plenty of ways to provide reverse protection. A series Schottky diode would be more reliable than any of the relay based solutions. Whatever you do, a fuse or polyswitch is highly recommended, maybe 0.5A to the main rig and 3A for the IRF510's. ? ?? The PFET is often a good solution, particularly on a small battery powered QRP rig with a common 12v line to everything including the finals where you don't want to lose the 0.3v ?V-forward of a Schottky diode. If that's what you plan to do with your *Bitx*, the PFET may be the way to go. Jerry, KE7ER On Tue, Dec 12, 2017 at 08:59 am, Ashhar Farhan wrote:
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Purpose of this "reverse voltage discussion" has been to occupy minds and keyboards while waiting for uBITX to ship.??? 8-) _._ On Tue, Dec 12, 2017 at 9:59 AM, Ashhar Farhan <farhanbox@...> wrote:
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Weird there would be so many opinions on how best to solve such a simple problem.
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I've got a half dozen more really good solutions ready to go. Lots of other stuff to figure out, but this one involves a much lower thinking/typing ratio. Jerry, KE7ER On Tue, Dec 12, 2017 at 10:00 am, Arv Evans wrote:
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philip yates
What happened to the idea of putting a 4 pin rectifier in the incoming wiring. Phil - G7BZD On Tue, Dec 12, 2017 at 6:11 PM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote: Weird there would be so many opinions on how best to solve such a simple problem. |
Don, ND6T
Raj vu2zap
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