bitrex wrote: ==========> > >> Here's the power supply section of a Korg MS2000 synthesizer, I worked > >> on one one time that somebody had plugged an AC adapter of unknown type > >> into, as I recall the list of fucked components was long, some bits like > >> the SMT input filter and diode were rattling around in the enclosure, F1 > >> was done, IC15 was done, FU1 was open, fortunately no damage to the CPU > >> or DSP though. > > > > ** Long time ago, I was sent a Korg analog synth for repair that was the *victim* of a main power accident. > > A faulty ( home made ) extension lead had exploded a 12 inch length of ground track on the PCB along with a cup full of ICs, tantalum caps, diodes etc. Took quite some time, but I eventually fixed it. > > I remember the young owner was grumpy about the fee. > > > > ...... Phil> Sounds like you had to rebuild most of the internal power supply-bits,** IIRC the damage was mostly in the audio output and frequency generation sections. The Korg synth was correctly earthed, the tube amplifier it fed was using the bad AC lead. High 50Hz current flowed to mains safety ground via the Korg's audio output jack and earthed PCB traces. .... Phil
Rail-splitting a wall wart
Started by ●February 3, 2023
Reply by ●February 7, 20232023-02-07
Reply by ●February 7, 20232023-02-07
On Tue, 7 Feb 2023 19:02:58 -0500, bitrex <user@example.net> wrote:>On 2/7/2023 12:35 PM, John Larkin wrote: >> On Tue, 7 Feb 2023 02:48:47 -0500, Phil Hobbs >> <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >>> On 2023-02-06 20:11, whit3rd wrote: >>>> On Monday, February 6, 2023 at 3:38:45 PM UTC-8, John Larkin wrote: >>>>> On Mon, 6 Feb 2023 15:28:31 -0800 (PST), Phil Allison >>>>> <palli...@gmail.com> wrote: >>>> >>>> >>>>>> There is no such thing as " wrong" polarity when DC plugs are fitted to leads. >>>>>> Some are positive tip and the rest negative. >>>>>> Wot planet do you live on ? >>>> >>>>> We buy DC warts that have the inner part of the barrel connector >>>>> positive. Negative would certainly be wrong. >>>> >>>> That's a flawed certainty. >>>> Here is a counterexample; the center is negative, and it isn't just >>>> the label, my multimeter says so too. >>>> >>>> <https://photos.app.goo.gl/7RSyQpJ4NQrKzfgu5> >>>> >>>> What's really spooky, is that I recall an identical manufacturer and part number unit >>>> with center positive (also correctly labelled). >>>> >>> >>> A P-channel FET or a series Schottky diode fixes that. I'd never omit >>> polarity protection from any design--even my hand-wired protos have >>> shunt 1N5819s or 1N5823s. >>> >>> I don't use shunt diodes in products or customer designs--in the >>> low-noise instruments world, it's far from unknown for people to power >>> 24V stuff from two boat batteries in series. >>> >>> Interesting point, though--it might be a good idea to put an NFET in the >>> negative lead as well as a PFET in the positive one, to protect against >>> shorts from V- to ground. It could be a depletion device to guarantee >>> startup behavior. I'll think about that. >>> >>> Cheers >>> >>> Phil Hobbs >> >> I generally use a polyfuse and a big unipolar TVS first thing. That >> handles reverse voltage and some (not all) over-voltage cases. But I'd >> rather have the TVS fail shorted, than blow up everything downstream. >> >> TVS shorted can be blamed on the customer! >> >> Bulletproof startup can be challenging. > > >Sounds like an application for an SPLD with analog comparators and state >machine, e.g. > ><https://www.mouser.com/datasheet/2/698/SLG46537r106_05242017_1141056-2956193.pdf> > >They're about 50 cents in quantity programmed. 8 states seems like >enough to build a little fault tree that could quickly determine the >most common disallowed states (over or under-voltage, reverse polarity, >AC plugged in instead of DC) and respond appropriatelyWhere would it get its power from?
Reply by ●February 7, 20232023-02-07
On Tue, 7 Feb 2023 13:23:46 -0500, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>On 2023-02-07 12:35, John Larkin wrote: >> On Tue, 7 Feb 2023 02:48:47 -0500, Phil Hobbs >> <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >>> On 2023-02-06 20:11, whit3rd wrote: >>>> On Monday, February 6, 2023 at 3:38:45 PM UTC-8, John Larkin wrote: >>>>> On Mon, 6 Feb 2023 15:28:31 -0800 (PST), Phil Allison >>>>> <palli...@gmail.com> wrote: >>>> >>>> >>>>>> There is no such thing as " wrong" polarity when DC plugs are fitted to leads. >>>>>> Some are positive tip and the rest negative. >>>>>> Wot planet do you live on ? >>>> >>>>> We buy DC warts that have the inner part of the barrel connector >>>>> positive. Negative would certainly be wrong. >>>> >>>> That's a flawed certainty. >>>> Here is a counterexample; the center is negative, and it isn't just >>>> the label, my multimeter says so too. >>>> >>>> <https://photos.app.goo.gl/7RSyQpJ4NQrKzfgu5> >>>> >>>> What's really spooky, is that I recall an identical manufacturer and part number unit >>>> with center positive (also correctly labelled). >>>> >>> >>> A P-channel FET or a series Schottky diode fixes that. I'd never omit >>> polarity protection from any design--even my hand-wired protos have >>> shunt 1N5819s or 1N5823s. >>> >>> I don't use shunt diodes in products or customer designs--in the >>> low-noise instruments world, it's far from unknown for people to power >>> 24V stuff from two boat batteries in series. >>> >>> Interesting point, though--it might be a good idea to put an NFET in the >>> negative lead as well as a PFET in the positive one, to protect against >>> shorts from V- to ground. It could be a depletion device to guarantee >>> startup behavior. I'll think about that. >>> > >> I generally use a polyfuse and a big unipolar TVS first thing. That >> handles reverse voltage and some (not all) over-voltage cases. But I'd >> rather have the TVS fail shorted, than blow up everything downstream. >> >> TVS shorted can be blamed on the customer! >> >> Bulletproof startup can be challenging. >> >> We hard-ground everything in our boxes and assume that a customer >> might want to power us from their, usually grounded, roughly 24 volt >> DC buss. > >We often do that too, and used to do it more when we could still get >PolyZens, which were a wonderfully complete and compact solution >(*sniff* *sniff*). > >A big TVS can desolder itself and fall off the board if the PCB is >vertical. > >Most of our stuff has switchers and lots of filtering, and so runs fine >off a common power buss. The rail splitter thing is for light-duty use. > >Cheers > >Phil HobbsTake a look at IXYS CPC1540GS. It's a high-voltage bidirectional SSR with current and thermal limiting. I've used it as just a current limiter. This and a TVS might be a nice combination. Drive the LED side with a resistor or a depletion fet. Some clever LED-side driver might do under/overvoltage lockout too.
Reply by ●February 7, 20232023-02-07
On Tue, 7 Feb 2023 20:50:18 +0000, piglet <erichpwagner@hotmail.com> wrote:>On 07/02/2023 6:01 pm, Jan Panteltje wrote: >> On a sunny day (Tue, 07 Feb 2023 09:41:50 -0800) it happened John Larkin >> <jlarkin@highlandSNIPMEtechnology.com> wrote in >> <8v25uh57g2p2il0gcb6chtfc5odrdgvlas@4ax.com>: >> >>> USB-C is great. It's truly universal and can be mated first try in the >>> dark. It's data line compatible with old USB connectors and provides 5 >>> volts if you want it. >> >> USB-C sucks, my smartphone has it and already one time I did not put the connector >> in far enough and it had not charged.Well, don't do that. It seems to gave a pretty good detent feel.>> Its too small for real power, how many times can you put that stuff in? >> I already had an other problem with a normal USB cable just hours ago. >> Oh and again yesterday with a USB hub that had switched off ports.. >> OK it is all intensively used, but even your phone is plugged in >> for charging on a daily bases, so 365 times a year. >> Mechanical wear.. electrical damage / burn in to contacts ..what not >> I was thinking about wireless charging but that sucks too as it causes even more RF ..Wireless phone charger pads are cool. Mine charges about 2x as fast as a USB cable from my PC and is really easy to use. They run at roughly 150 KHz, near-field magnetic coupling, so won't radiate much.>> We really need fusion powered eternal batteries and fusion powered cars. >> >> Wallwarts are OK, I have some big ones for LED strips for room lighting. >> The small ones I have from Reichelt have a switch to select the voltage >> and came with a bunch of adaptors but you can put those in + / - reversed. >> http://panteltje.com/pub/universal_wart_IXIMG_0879.JPG >> So use a bridge rectifier in your gadget, should be OK. >> >> >> > >USB-C has 24 pins on 0.5mm pitch on something that rattles around in >overcoat pockets and handbags. Sure sounds like great recipe for robust >and reliable contact </sarcasm> > >pigletIn my experience, it is robust and reliable.
Reply by ●February 8, 20232023-02-08
On 2/7/2023 10:29 PM, John Larkin wrote:> On Tue, 7 Feb 2023 19:02:58 -0500, bitrex <user@example.net> wrote: > >> On 2/7/2023 12:35 PM, John Larkin wrote: >>> On Tue, 7 Feb 2023 02:48:47 -0500, Phil Hobbs >>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>> >>>> On 2023-02-06 20:11, whit3rd wrote: >>>>> On Monday, February 6, 2023 at 3:38:45 PM UTC-8, John Larkin wrote: >>>>>> On Mon, 6 Feb 2023 15:28:31 -0800 (PST), Phil Allison >>>>>> <palli...@gmail.com> wrote: >>>>> >>>>> >>>>>>> There is no such thing as " wrong" polarity when DC plugs are fitted to leads. >>>>>>> Some are positive tip and the rest negative. >>>>>>> Wot planet do you live on ? >>>>> >>>>>> We buy DC warts that have the inner part of the barrel connector >>>>>> positive. Negative would certainly be wrong. >>>>> >>>>> That's a flawed certainty. >>>>> Here is a counterexample; the center is negative, and it isn't just >>>>> the label, my multimeter says so too. >>>>> >>>>> <https://photos.app.goo.gl/7RSyQpJ4NQrKzfgu5> >>>>> >>>>> What's really spooky, is that I recall an identical manufacturer and part number unit >>>>> with center positive (also correctly labelled). >>>>> >>>> >>>> A P-channel FET or a series Schottky diode fixes that. I'd never omit >>>> polarity protection from any design--even my hand-wired protos have >>>> shunt 1N5819s or 1N5823s. >>>> >>>> I don't use shunt diodes in products or customer designs--in the >>>> low-noise instruments world, it's far from unknown for people to power >>>> 24V stuff from two boat batteries in series. >>>> >>>> Interesting point, though--it might be a good idea to put an NFET in the >>>> negative lead as well as a PFET in the positive one, to protect against >>>> shorts from V- to ground. It could be a depletion device to guarantee >>>> startup behavior. I'll think about that. >>>> >>>> Cheers >>>> >>>> Phil Hobbs >>> >>> I generally use a polyfuse and a big unipolar TVS first thing. That >>> handles reverse voltage and some (not all) over-voltage cases. But I'd >>> rather have the TVS fail shorted, than blow up everything downstream. >>> >>> TVS shorted can be blamed on the customer! >>> >>> Bulletproof startup can be challenging. >> >> >> Sounds like an application for an SPLD with analog comparators and state >> machine, e.g. >> >> <https://www.mouser.com/datasheet/2/698/SLG46537r106_05242017_1141056-2956193.pdf> >> >> They're about 50 cents in quantity programmed. 8 states seems like >> enough to build a little fault tree that could quickly determine the >> most common disallowed states (over or under-voltage, reverse polarity, >> AC plugged in instead of DC) and respond appropriately > > > Where would it get its power from? >I was thinking something like a 1N00x bridge followed by resistor + zener and float it, connected ahead of a normally-open DPDT relay that's in line with the rest of the circuit. That plus a dual optocoupler and few other parts seems like it should be enough to detect reverse polarity and AC, and then close the relay once that checks out and over/under voltage comparisons also good
Reply by ●February 8, 20232023-02-08
On Wed, 8 Feb 2023 00:40:26 -0500, bitrex <user@example.net> wrote:>On 2/7/2023 10:29 PM, John Larkin wrote: >> On Tue, 7 Feb 2023 19:02:58 -0500, bitrex <user@example.net> wrote: >> >>> On 2/7/2023 12:35 PM, John Larkin wrote: >>>> On Tue, 7 Feb 2023 02:48:47 -0500, Phil Hobbs >>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>> >>>>> On 2023-02-06 20:11, whit3rd wrote: >>>>>> On Monday, February 6, 2023 at 3:38:45 PM UTC-8, John Larkin wrote: >>>>>>> On Mon, 6 Feb 2023 15:28:31 -0800 (PST), Phil Allison >>>>>>> <palli...@gmail.com> wrote: >>>>>> >>>>>> >>>>>>>> There is no such thing as " wrong" polarity when DC plugs are fitted to leads. >>>>>>>> Some are positive tip and the rest negative. >>>>>>>> Wot planet do you live on ? >>>>>> >>>>>>> We buy DC warts that have the inner part of the barrel connector >>>>>>> positive. Negative would certainly be wrong. >>>>>> >>>>>> That's a flawed certainty. >>>>>> Here is a counterexample; the center is negative, and it isn't just >>>>>> the label, my multimeter says so too. >>>>>> >>>>>> <https://photos.app.goo.gl/7RSyQpJ4NQrKzfgu5> >>>>>> >>>>>> What's really spooky, is that I recall an identical manufacturer and part number unit >>>>>> with center positive (also correctly labelled). >>>>>> >>>>> >>>>> A P-channel FET or a series Schottky diode fixes that. I'd never omit >>>>> polarity protection from any design--even my hand-wired protos have >>>>> shunt 1N5819s or 1N5823s. >>>>> >>>>> I don't use shunt diodes in products or customer designs--in the >>>>> low-noise instruments world, it's far from unknown for people to power >>>>> 24V stuff from two boat batteries in series. >>>>> >>>>> Interesting point, though--it might be a good idea to put an NFET in the >>>>> negative lead as well as a PFET in the positive one, to protect against >>>>> shorts from V- to ground. It could be a depletion device to guarantee >>>>> startup behavior. I'll think about that. >>>>> >>>>> Cheers >>>>> >>>>> Phil Hobbs >>>> >>>> I generally use a polyfuse and a big unipolar TVS first thing. That >>>> handles reverse voltage and some (not all) over-voltage cases. But I'd >>>> rather have the TVS fail shorted, than blow up everything downstream. >>>> >>>> TVS shorted can be blamed on the customer! >>>> >>>> Bulletproof startup can be challenging. >>> >>> >>> Sounds like an application for an SPLD with analog comparators and state >>> machine, e.g. >>> >>> <https://www.mouser.com/datasheet/2/698/SLG46537r106_05242017_1141056-2956193.pdf> >>> >>> They're about 50 cents in quantity programmed. 8 states seems like >>> enough to build a little fault tree that could quickly determine the >>> most common disallowed states (over or under-voltage, reverse polarity, >>> AC plugged in instead of DC) and respond appropriately >> >> >> Where would it get its power from? >> > > >I was thinking something like a 1N00x bridge followed by resistor + >zener and float it, connected ahead of a normally-open DPDT relay that's >in line with the rest of the circuit. > >That plus a dual optocoupler and few other parts seems like it should be >enough to detect reverse polarity and AC, and then close the relay once >that checks out and over/under voltage comparisons also goodThat could work if all the details were right and it wasn't too complex. The uP power need not be floating if reverse polarity were handled right, like a series diode or equivalent... pfet maybe. It could be a product, a universal over/under/reverse/overcurrent protector. It may as well do the powerup reset function, which is hard to do right. I'll do the circuit design if you'll program it. You could sell them. One could sell the cpu alone or a little pc board with everything. I might buy some. That could be a new market, power inlet boards that solve all the problems. One version could include USB-C connector and negotiation. A version might make +3.3 or +-10 or something like that. It's shocking that nothing like this seems to exist.
Reply by ●February 8, 20232023-02-08
On 2023-02-07 22:34, John Larkin wrote:> On Tue, 7 Feb 2023 13:23:46 -0500, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> On 2023-02-07 12:35, John Larkin wrote: >>> On Tue, 7 Feb 2023 02:48:47 -0500, Phil Hobbs >>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>> >>>> On 2023-02-06 20:11, whit3rd wrote: >>>>> On Monday, February 6, 2023 at 3:38:45 PM UTC-8, John Larkin wrote: >>>>>> On Mon, 6 Feb 2023 15:28:31 -0800 (PST), Phil Allison >>>>>> <palli...@gmail.com> wrote: >>>>> >>>>> >>>>>>> There is no such thing as " wrong" polarity when DC plugs are fitted to leads. >>>>>>> Some are positive tip and the rest negative. >>>>>>> Wot planet do you live on ? >>>>> >>>>>> We buy DC warts that have the inner part of the barrel connector >>>>>> positive. Negative would certainly be wrong. >>>>> >>>>> That's a flawed certainty. >>>>> Here is a counterexample; the center is negative, and it isn't just >>>>> the label, my multimeter says so too. >>>>> >>>>> <https://photos.app.goo.gl/7RSyQpJ4NQrKzfgu5> >>>>> >>>>> What's really spooky, is that I recall an identical manufacturer and part number unit >>>>> with center positive (also correctly labelled). >>>>> >>>> >>>> A P-channel FET or a series Schottky diode fixes that. I'd never omit >>>> polarity protection from any design--even my hand-wired protos have >>>> shunt 1N5819s or 1N5823s. >>>> >>>> I don't use shunt diodes in products or customer designs--in the >>>> low-noise instruments world, it's far from unknown for people to power >>>> 24V stuff from two boat batteries in series. >>>> >>>> Interesting point, though--it might be a good idea to put an NFET in the >>>> negative lead as well as a PFET in the positive one, to protect against >>>> shorts from V- to ground. It could be a depletion device to guarantee >>>> startup behavior. I'll think about that. >>>> >> >>> I generally use a polyfuse and a big unipolar TVS first thing. That >>> handles reverse voltage and some (not all) over-voltage cases. But I'd >>> rather have the TVS fail shorted, than blow up everything downstream. >>> >>> TVS shorted can be blamed on the customer! >>> >>> Bulletproof startup can be challenging. >>> >>> We hard-ground everything in our boxes and assume that a customer >>> might want to power us from their, usually grounded, roughly 24 volt >>> DC buss. >> >> We often do that too, and used to do it more when we could still get >> PolyZens, which were a wonderfully complete and compact solution >> (*sniff* *sniff*). >> >> A big TVS can desolder itself and fall off the board if the PCB is >> vertical. >> >> Most of our stuff has switchers and lots of filtering, and so runs fine >> off a common power buss. The rail splitter thing is for light-duty use. >> >> Cheers >> >> Phil Hobbs > > Take a look at IXYS CPC1540GS. > > It's a high-voltage bidirectional SSR with current and thermal > limiting. > > I've used it as just a current limiter. This and a TVS might be a nice > combination. Drive the LED side with a resistor or a depletion fet. > > Some clever LED-side driver might do under/overvoltage lockout too. >Nice part, but its maximum Ron of 25 ohms is on the high side. Thanks Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Reply by ●February 8, 20232023-02-08
On Wed, 8 Feb 2023 13:57:10 -0500, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>On 2023-02-07 22:34, John Larkin wrote: >> On Tue, 7 Feb 2023 13:23:46 -0500, Phil Hobbs >> <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >>> On 2023-02-07 12:35, John Larkin wrote: >>>> On Tue, 7 Feb 2023 02:48:47 -0500, Phil Hobbs >>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>> >>>>> On 2023-02-06 20:11, whit3rd wrote: >>>>>> On Monday, February 6, 2023 at 3:38:45 PM UTC-8, John Larkin wrote: >>>>>>> On Mon, 6 Feb 2023 15:28:31 -0800 (PST), Phil Allison >>>>>>> <palli...@gmail.com> wrote: >>>>>> >>>>>> >>>>>>>> There is no such thing as " wrong" polarity when DC plugs are fitted to leads. >>>>>>>> Some are positive tip and the rest negative. >>>>>>>> Wot planet do you live on ? >>>>>> >>>>>>> We buy DC warts that have the inner part of the barrel connector >>>>>>> positive. Negative would certainly be wrong. >>>>>> >>>>>> That's a flawed certainty. >>>>>> Here is a counterexample; the center is negative, and it isn't just >>>>>> the label, my multimeter says so too. >>>>>> >>>>>> <https://photos.app.goo.gl/7RSyQpJ4NQrKzfgu5> >>>>>> >>>>>> What's really spooky, is that I recall an identical manufacturer and part number unit >>>>>> with center positive (also correctly labelled). >>>>>> >>>>> >>>>> A P-channel FET or a series Schottky diode fixes that. I'd never omit >>>>> polarity protection from any design--even my hand-wired protos have >>>>> shunt 1N5819s or 1N5823s. >>>>> >>>>> I don't use shunt diodes in products or customer designs--in the >>>>> low-noise instruments world, it's far from unknown for people to power >>>>> 24V stuff from two boat batteries in series. >>>>> >>>>> Interesting point, though--it might be a good idea to put an NFET in the >>>>> negative lead as well as a PFET in the positive one, to protect against >>>>> shorts from V- to ground. It could be a depletion device to guarantee >>>>> startup behavior. I'll think about that. >>>>> >>> >>>> I generally use a polyfuse and a big unipolar TVS first thing. That >>>> handles reverse voltage and some (not all) over-voltage cases. But I'd >>>> rather have the TVS fail shorted, than blow up everything downstream. >>>> >>>> TVS shorted can be blamed on the customer! >>>> >>>> Bulletproof startup can be challenging. >>>> >>>> We hard-ground everything in our boxes and assume that a customer >>>> might want to power us from their, usually grounded, roughly 24 volt >>>> DC buss. >>> >>> We often do that too, and used to do it more when we could still get >>> PolyZens, which were a wonderfully complete and compact solution >>> (*sniff* *sniff*). >>> >>> A big TVS can desolder itself and fall off the board if the PCB is >>> vertical. >>> >>> Most of our stuff has switchers and lots of filtering, and so runs fine >>> off a common power buss. The rail splitter thing is for light-duty use. >>> >>> Cheers >>> >>> Phil Hobbs >> >> Take a look at IXYS CPC1540GS. >> >> It's a high-voltage bidirectional SSR with current and thermal >> limiting. >> >> I've used it as just a current limiter. This and a TVS might be a nice >> combination. Drive the LED side with a resistor or a depletion fet. >> >> Some clever LED-side driver might do under/overvoltage lockout too. >> > >Nice part, but its maximum Ron of 25 ohms is on the high side. > >Thanks > >Phil HobbsIt's 4 ohms in unipolar mode, which is better but doesn't do reverse protection the obvious way. I want a higher-power version. Consider, maybe, a biggish SSR and a small ssr or optocoupler to measure the ON voltage drop for shutdown.
Reply by ●February 8, 20232023-02-08
On 2/8/2023 10:34 AM, John Larkin wrote:> On Wed, 8 Feb 2023 00:40:26 -0500, bitrex <user@example.net> wrote: > >> On 2/7/2023 10:29 PM, John Larkin wrote: >>> On Tue, 7 Feb 2023 19:02:58 -0500, bitrex <user@example.net> wrote: >>> >>>> On 2/7/2023 12:35 PM, John Larkin wrote: >>>>> On Tue, 7 Feb 2023 02:48:47 -0500, Phil Hobbs >>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>>> >>>>>> On 2023-02-06 20:11, whit3rd wrote: >>>>>>> On Monday, February 6, 2023 at 3:38:45 PM UTC-8, John Larkin wrote: >>>>>>>> On Mon, 6 Feb 2023 15:28:31 -0800 (PST), Phil Allison >>>>>>>> <palli...@gmail.com> wrote: >>>>>>> >>>>>>> >>>>>>>>> There is no such thing as " wrong" polarity when DC plugs are fitted to leads. >>>>>>>>> Some are positive tip and the rest negative. >>>>>>>>> Wot planet do you live on ? >>>>>>> >>>>>>>> We buy DC warts that have the inner part of the barrel connector >>>>>>>> positive. Negative would certainly be wrong. >>>>>>> >>>>>>> That's a flawed certainty. >>>>>>> Here is a counterexample; the center is negative, and it isn't just >>>>>>> the label, my multimeter says so too. >>>>>>> >>>>>>> <https://photos.app.goo.gl/7RSyQpJ4NQrKzfgu5> >>>>>>> >>>>>>> What's really spooky, is that I recall an identical manufacturer and part number unit >>>>>>> with center positive (also correctly labelled). >>>>>>> >>>>>> >>>>>> A P-channel FET or a series Schottky diode fixes that. I'd never omit >>>>>> polarity protection from any design--even my hand-wired protos have >>>>>> shunt 1N5819s or 1N5823s. >>>>>> >>>>>> I don't use shunt diodes in products or customer designs--in the >>>>>> low-noise instruments world, it's far from unknown for people to power >>>>>> 24V stuff from two boat batteries in series. >>>>>> >>>>>> Interesting point, though--it might be a good idea to put an NFET in the >>>>>> negative lead as well as a PFET in the positive one, to protect against >>>>>> shorts from V- to ground. It could be a depletion device to guarantee >>>>>> startup behavior. I'll think about that. >>>>>> >>>>>> Cheers >>>>>> >>>>>> Phil Hobbs >>>>> >>>>> I generally use a polyfuse and a big unipolar TVS first thing. That >>>>> handles reverse voltage and some (not all) over-voltage cases. But I'd >>>>> rather have the TVS fail shorted, than blow up everything downstream. >>>>> >>>>> TVS shorted can be blamed on the customer! >>>>> >>>>> Bulletproof startup can be challenging. >>>> >>>> >>>> Sounds like an application for an SPLD with analog comparators and state >>>> machine, e.g. >>>> >>>> <https://www.mouser.com/datasheet/2/698/SLG46537r106_05242017_1141056-2956193.pdf> >>>> >>>> They're about 50 cents in quantity programmed. 8 states seems like >>>> enough to build a little fault tree that could quickly determine the >>>> most common disallowed states (over or under-voltage, reverse polarity, >>>> AC plugged in instead of DC) and respond appropriately >>> >>> >>> Where would it get its power from? >>> >> >> >> I was thinking something like a 1N00x bridge followed by resistor + >> zener and float it, connected ahead of a normally-open DPDT relay that's >> in line with the rest of the circuit. >> >> That plus a dual optocoupler and few other parts seems like it should be >> enough to detect reverse polarity and AC, and then close the relay once >> that checks out and over/under voltage comparisons also good > > That could work if all the details were right and it wasn't too > complex. The uP power need not be floating if reverse polarity were > handled right, like a series diode or equivalent... pfet maybe. > > It could be a product, a universal over/under/reverse/overcurrent > protector. It may as well do the powerup reset function, which is hard > to do right. > > I'll do the circuit design if you'll program it. You could sell them. > One could sell the cpu alone or a little pc board with everything. I > might buy some. > > That could be a new market, power inlet boards that solve all the > problems. One version could include USB-C connector and negotiation. A > version might make +3.3 or +-10 or something like that.Not the kind of mission-critical product I think I'd want to personally take responsibility for selling as some kind of black box-ish module at this time given, as you say, the details need to be right. I think such a design (even just the "code" part) would need more than just my eyes on it to ensure that, and more time testing than I'm willing to commit ATM. But if you have ideas of what an implementation might look like on the analog side I can post a "code" sketch this month, and people could make closed-source derivatives if they like. Honestly the Greenpak Designer is very straightforward to get a handle on, and as its mixed-signal designs simulate more like SPICE than an FPGA sim.> It's shocking that nothing like this seems to exist.There are a bunch of overvoltage/reverse polarity protection ICs availabe; most seem geared to automotive applications where the hazards are mainly load dumps and someone connecting the 12 volt battery backwards, relays obviously aren't helpful to defend against the type of over/under voltage conditions caused by load dump transients.
Reply by ●February 8, 20232023-02-08
On 2023-02-08 15:05, John Larkin wrote:> On Wed, 8 Feb 2023 13:57:10 -0500, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> On 2023-02-07 22:34, John Larkin wrote: >>> On Tue, 7 Feb 2023 13:23:46 -0500, Phil Hobbs >>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>> >>>> On 2023-02-07 12:35, John Larkin wrote: >>>>> On Tue, 7 Feb 2023 02:48:47 -0500, Phil Hobbs >>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>>> >>>>>> On 2023-02-06 20:11, whit3rd wrote: >>>>>>> On Monday, February 6, 2023 at 3:38:45 PM UTC-8, John Larkin wrote: >>>>>>>> On Mon, 6 Feb 2023 15:28:31 -0800 (PST), Phil Allison >>>>>>>> <palli...@gmail.com> wrote: >>>>>>> >>>>>>> >>>>>>>>> There is no such thing as " wrong" polarity when DC plugs are fitted to leads. >>>>>>>>> Some are positive tip and the rest negative. >>>>>>>>> Wot planet do you live on ? >>>>>>> >>>>>>>> We buy DC warts that have the inner part of the barrel connector >>>>>>>> positive. Negative would certainly be wrong. >>>>>>> >>>>>>> That's a flawed certainty. >>>>>>> Here is a counterexample; the center is negative, and it isn't just >>>>>>> the label, my multimeter says so too. >>>>>>> >>>>>>> <https://photos.app.goo.gl/7RSyQpJ4NQrKzfgu5> >>>>>>> >>>>>>> What's really spooky, is that I recall an identical manufacturer and part number unit >>>>>>> with center positive (also correctly labelled). >>>>>>> >>>>>> >>>>>> A P-channel FET or a series Schottky diode fixes that. I'd never omit >>>>>> polarity protection from any design--even my hand-wired protos have >>>>>> shunt 1N5819s or 1N5823s. >>>>>> >>>>>> I don't use shunt diodes in products or customer designs--in the >>>>>> low-noise instruments world, it's far from unknown for people to power >>>>>> 24V stuff from two boat batteries in series. >>>>>> >>>>>> Interesting point, though--it might be a good idea to put an NFET in the >>>>>> negative lead as well as a PFET in the positive one, to protect against >>>>>> shorts from V- to ground. It could be a depletion device to guarantee >>>>>> startup behavior. I'll think about that. >>>>>> >>>> >>>>> I generally use a polyfuse and a big unipolar TVS first thing. That >>>>> handles reverse voltage and some (not all) over-voltage cases. But I'd >>>>> rather have the TVS fail shorted, than blow up everything downstream. >>>>> >>>>> TVS shorted can be blamed on the customer! >>>>> >>>>> Bulletproof startup can be challenging. >>>>> >>>>> We hard-ground everything in our boxes and assume that a customer >>>>> might want to power us from their, usually grounded, roughly 24 volt >>>>> DC buss. >>>> >>>> We often do that too, and used to do it more when we could still get >>>> PolyZens, which were a wonderfully complete and compact solution >>>> (*sniff* *sniff*). >>>> >>>> A big TVS can desolder itself and fall off the board if the PCB is >>>> vertical. >>>> >>>> Most of our stuff has switchers and lots of filtering, and so runs fine >>>> off a common power buss. The rail splitter thing is for light-duty use. >>>> >>>> Cheers >>>> >>>> Phil Hobbs >>> >>> Take a look at IXYS CPC1540GS. >>> >>> It's a high-voltage bidirectional SSR with current and thermal >>> limiting. >>> >>> I've used it as just a current limiter. This and a TVS might be a nice >>> combination. Drive the LED side with a resistor or a depletion fet. >>> >>> Some clever LED-side driver might do under/overvoltage lockout too. >>> >> >> Nice part, but its maximum Ron of 25 ohms is on the high side.> > It's 4 ohms in unipolar mode, which is better but doesn't do reverse > protection the obvious way. > > I want a higher-power version. > > Consider, maybe, a biggish SSR and a small ssr or optocoupler to > measure the ON voltage drop for shutdown. >Nah, I'll stick with 70 cents worth of small FETs and a resistor pack for the grounded-wart fault condition, and let the polyfuse look after overcurrent. The TCA0372 will be pretty much loafing at current levels I care about for this use. The FETs would be cheaper still except that I need >24 V_GSmax--for PFETs, I wound up with DMP3056es for all three, and for NFETs, DMG3406L pass devices and a MCC 2N7002A driver. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
