On Wed, 8 Feb 2023 19:35:19 -0500, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>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 HobbsThis really isn't bad. https://www.dropbox.com/s/fc7l364cw4i64lg/Wart_Limiter_2.jpg?raw=1 A variation would be to make the diode a TVS and trigger the SCR after the over-voltage was there for a while, before the TVS fries.
Rail-splitting a wall wart
Started by ●February 3, 2023
Reply by ●February 8, 20232023-02-08
Reply by ●February 8, 20232023-02-08
On Wed, 08 Feb 2023 19:33:03 -0800, John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:>On Wed, 8 Feb 2023 19:35:19 -0500, Phil Hobbs ><pcdhSpamMeSenseless@electrooptical.net> wrote: > >>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 > >This really isn't bad. > >https://www.dropbox.com/s/fc7l364cw4i64lg/Wart_Limiter_2.jpg?raw=1 > >A variation would be to make the diode a TVS and trigger the SCR after >the over-voltage was there for a while, before the TVS fries. >Or dump the big diode and use a triac.
Reply by ●February 9, 20232023-02-09
On 2023-02-08 22:33, John Larkin wrote:> On Wed, 8 Feb 2023 19:35:19 -0500, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> 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. >>> > This really isn't bad. > > https://www.dropbox.com/s/fc7l364cw4i64lg/Wart_Limiter_2.jpg?raw=1 > > A variation would be to make the diode a TVS and trigger the SCR after > the over-voltage was there for a while, before the TVS fries. >Fun. "Go ahead, wallwart--make my day." ;) 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
Reply by ●February 9, 20232023-02-09
On Wednesday, February 8, 2023 at 7:33:14 PM UTC-8, John Larkin wrote: [about power inlet protection]> This really isn't bad. > > https://www.dropbox.com/s/fc7l364cw4i64lg/Wart_Limiter_2.jpg?raw=1 > > A variation would be to make the diode a TVS and trigger the SCR after > the over-voltage was there for a while, before the TVS fries.Me, I'd stick with two zeners and a resistor. For polarity reversal, and overvoltage, make it a fusible resistor.
Reply by ●February 9, 20232023-02-09
On a sunny day (Wed, 8 Feb 2023 22:23:58 -0800 (PST)) it happened whit3rd <whit3rd@gmail.com> wrote in <5424037b-6d8a-4349-8b2b-d41694619d6en@googlegroups.com>:>On Wednesday, February 8, 2023 at 7:33:14 PM UTC-8, John Larkin wrote: >[about power inlet protection] > >> This really isn't bad. >> >> https://www.dropbox.com/s/fc7l364cw4i64lg/Wart_Limiter_2.jpg?raw=1 >> >> A variation would be to make the diode a TVS and trigger the SCR after >> the over-voltage was there for a while, before the TVS fries. > >Me, I'd stick with two zeners and a resistor. For polarity reversal, and overvoltage, >make it a fusible resistor.Or mybe some indication light 'fuse blown' by using something with 2 LEDs across the fuse Just to inform the poor user.. LED1 / --|>|--- | | --R- | |--- | | --|<|--- \ LED2 mark one 'reverse polarity' ?
Reply by ●February 9, 20232023-02-09
On Wed, 8 Feb 2023 22:23:58 -0800 (PST), whit3rd <whit3rd@gmail.com> wrote:>On Wednesday, February 8, 2023 at 7:33:14 PM UTC-8, John Larkin wrote: >[about power inlet protection] > >> This really isn't bad. >> >> https://www.dropbox.com/s/fc7l364cw4i64lg/Wart_Limiter_2.jpg?raw=1 >> >> A variation would be to make the diode a TVS and trigger the SCR after >> the over-voltage was there for a while, before the TVS fries. > >Me, I'd stick with two zeners and a resistor. For polarity reversal, and overvoltage, >make it a fusible resistor.Then, when a user plugs in the wrong wart, the unit dies hard. That's exactly what we're trying to avoid. A polyfuse and a TVS is pretty good but is not safe in all cases. Seems to me that all resistors are fusible resistors.
Reply by ●February 9, 20232023-02-09
On Thu, 09 Feb 2023 07:30:42 GMT, Jan Panteltje <alien@comet.invalid> wrote:>On a sunny day (Wed, 8 Feb 2023 22:23:58 -0800 (PST)) it happened whit3rd ><whit3rd@gmail.com> wrote in ><5424037b-6d8a-4349-8b2b-d41694619d6en@googlegroups.com>: > >>On Wednesday, February 8, 2023 at 7:33:14 PM UTC-8, John Larkin wrote: >>[about power inlet protection] >> >>> This really isn't bad. >>> >>> https://www.dropbox.com/s/fc7l364cw4i64lg/Wart_Limiter_2.jpg?raw=1 >>> >>> A variation would be to make the diode a TVS and trigger the SCR after >>> the over-voltage was there for a while, before the TVS fries. >> >>Me, I'd stick with two zeners and a resistor. For polarity reversal, and overvoltage, >>make it a fusible resistor. > >Or mybe some indication light 'fuse blown' >by using something with 2 LEDs across the fuse >Just to inform the poor user.. > > LED1 > / > --|>|--- > | | >--R- | |--- > | | > --|<|--- > \ > LED2 > mark one 'reverse polarity' ?No, mark the LEDs on the outside of the box WARRANTY VOID + and WARRANTY VOID - Users will appreciate that.
Reply by ●February 9, 20232023-02-09
On Mon, 6 Feb 2023 13:30:00 -0000 (UTC), "Don" <g@crcomp.net> wrote:>whit3rd wrote: >> upsid...@downunder.com wrote: >> >>> Using an AC wall wart 50/60 Hz iron core transformer with special >>> connector will discourage many experimenters and their devices will >>> not work with AC, possibly releasing some smoke :-) >> >> An AC connector can be unpolarized, but no DC connector commonly is. >> So, you can fit an AC wart with reversible plug, and no DC wallwart is >> likely to be compatible. >> I've got a subwoofer that takes AC/DC input, it has a DC-like connector >> and full wave bridge... can't get the polarity wrong either. > >Even when the voltage and power matches, it can be difficult to find a >compatible connector. This thirty-four assortment of different sizes and >shapes to connect a nominal 19.5VDC adapter to a laptop fails to cover >all possible variances: > ><https://www.ebay.com/itm/314035139187> > >Danke,The obvious response is USB-C.
Reply by ●February 9, 20232023-02-09
John Larkin wrote:> Don wrote: >>whit3rd wrote: >>> upsid...@downunder.com wrote: >>> >>>> Using an AC wall wart 50/60 Hz iron core transformer with special >>>> connector will discourage many experimenters and their devices will >>>> not work with AC, possibly releasing some smoke :-) >>> >>> An AC connector can be unpolarized, but no DC connector commonly is. >>> So, you can fit an AC wart with reversible plug, and no DC wallwart is >>> likely to be compatible. >>> I've got a subwoofer that takes AC/DC input, it has a DC-like connector >>> and full wave bridge... can't get the polarity wrong either. >> >>Even when the voltage and power matches, it can be difficult to find a >>compatible connector. This thirty-four assortment of different sizes and >>shapes to connect a nominal 19.5VDC adapter to a laptop fails to cover >>all possible variances: >> >><https://www.ebay.com/itm/314035139187> > > The obvious response is USB-C.Your followup in turn leads to the intuitively obvious question: does USB-C supply 3.25A @ 19.5VDC? Hint: the assortment above pertains to laptop power adapters. Danke, -- Don, KB7RPU, https://www.qsl.net/kb7rpu There was a young lady named Bright Whose speed was far faster than light; She set out one day In a relative way And returned on the previous night.
Reply by ●February 9, 20232023-02-09
On 09/02/2023 15:10, Don wrote:> John Larkin wrote: >> Don wrote: >>> whit3rd wrote: >>>> upsid...@downunder.com wrote: >>>> >>>>> Using an AC wall wart 50/60 Hz iron core transformer with special >>>>> connector will discourage many experimenters and their devices will >>>>> not work with AC, possibly releasing some smoke :-) >>>> >>>> An AC connector can be unpolarized, but no DC connector commonly is. >>>> So, you can fit an AC wart with reversible plug, and no DC wallwart is >>>> likely to be compatible. >>>> I've got a subwoofer that takes AC/DC input, it has a DC-like connector >>>> and full wave bridge... can't get the polarity wrong either. >>> >>> Even when the voltage and power matches, it can be difficult to find a >>> compatible connector. This thirty-four assortment of different sizes and >>> shapes to connect a nominal 19.5VDC adapter to a laptop fails to cover >>> all possible variances: >>> >>> <https://www.ebay.com/itm/314035139187> >> >> The obvious response is USB-C. > > Your followup in turn leads to the intuitively obvious question: does > USB-C supply 3.25A @ 19.5VDC? > > Hint: the assortment above pertains to laptop power adapters. > > Danke, >Yep, potentially USB-C can negotiate up to 5A at 20V. However it could be as little as 5V 0.5A if for example an original USB-A supply is used with an adapter cable. piglet
