On Tue, 24 May 2022 10:43:08 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>John Walliker wrote: >> On Tuesday, 24 May 2022 at 09:08:21 UTC+1, whit3rd wrote: >>> On Monday, May 23, 2022 at 3:29:10 PM UTC-7, John Larkin wrote: >>>> On Mon, 23 May 2022 11:06:00 -0700 (PDT), whit3rd <whi...@gmail.com> >>>> wrote: >>>>> On Monday, May 23, 2022 at 10:19:30 AM UTC-7, John Larkin wrote: >>>>> >>>>>> I want an LED blinker to show that a high-voltage power supply is >>>>>> still dangerous. It should discharge the supply at some low current >>>>>> and blink from, say, 1400 volts down to maybe 40. >>>>> >>>>> So, a series string of fifteen current-limit diodes running a capacitor- >>>>> diac-LED blinkielight? S-272 seems suitable >>>>> >>>>> <https://www.mouser.com/datasheet/2/362/P22-23-CRD-1729293.pdf> >>>> The Supertex LND150 is a 500 volt depletion fet. A source resistor >>>> will program the current, and they can apparently be strung in series >>>> without problems. >>> Yeah, and a 'current-limit diode' is also a depletion FET. With a zener >>> limit specified (I'm not sure about LND150). Multiples only share >>> the voltage with such a matching zener specification. >>> >>> A resistor would work, too, but the alarm blinkie would change frequency >>> dramatically. >> >> Does anyone actually sell surface mount LND150s at the moment? All >> the usual suppliers seem to be out of stock for at least several months. >> >> John >> >TO-92s are good for the soul.Rarely! But we're using a TO-92 LM35 to measure the temp of a CPU cooler that we're using as a mosfet heat sink. We'll glue it to the side of the cooler and plug it into three little pin sockets.> >Cheers > >Phil Hobbs > >(Who just designed one into a supply-dictated board spin.) :(Are TO-92s easier to get than surfmount parts? At least it's an option. -- Anybody can count to one. - Robert Widlar
BJT behaviour at ridiculously low current levels
Started by ●May 11, 2022
Reply by ●May 24, 20222022-05-24
Reply by ●May 24, 20222022-05-24
On Tue, 24 May 2022 10:08:29 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>John Larkin wrote: >> On Mon, 23 May 2022 11:06:00 -0700 (PDT), whit3rd <whit3rd@gmail.com> >> wrote: >> >>> On Monday, May 23, 2022 at 10:19:30 AM UTC-7, John Larkin wrote: >>> >>>> I want an LED blinker to show that a high-voltage power supply is >>>> still dangerous. It should discharge the supply at some low current >>>> and blink from, say, 1400 volts down to maybe 40. >>> >>> So, a series string of fifteen current-limit diodes running a capacitor- >>> diac-LED blinkielight? S-272 seems suitable >>> >>> <https://www.mouser.com/datasheet/2/362/P22-23-CRD-1729293.pdf> >> >> The Supertex LND150 is a 500 volt depletion fet. A source resistor >> will program the current, and they can apparently be strung in series >> without problems. >> >> Three of them would do. They are around 30 cents each. >> >> A spin on Piglet's circuit might to the blinker. >> > >I'd probably be happier with a gate bias string to force the voltages to >equalize. Of course the resistors would have to be physically quite >large to take the voltage. > >Cheers > >Phil HobbsSomebody told me (was it you?) that they are OK in series. One or two may avalanche somewhere above 500 volts and one will actually regulate the current. I'm talking 50 or 100 uA in my case. -- Anybody can count to one. - Robert Widlar
Reply by ●May 24, 20222022-05-24
On Tue, 24 May 2022 07:25:20 -0700 (PDT), John Walliker <jrwalliker@gmail.com> wrote:>On Tuesday, 24 May 2022 at 15:05:31 UTC+1, jla...@highlandsniptechnology.com wrote: >> On Tue, 24 May 2022 05:53:02 -0700 (PDT), John Walliker > >> >Does anyone actually sell surface mount LND150s at the moment? All >> >the usual suppliers seem to be out of stock for at least several months. >> > >> >John >> Mouser has LND250s, basically the same part. > >Thank you - JohnWe have 2500 in stock. I could spare a few to anyone who wants to play with them. -- If a man will begin with certainties, he shall end with doubts, but if he will be content to begin with doubts he shall end in certainties. Francis Bacon
Reply by ●May 24, 20222022-05-24
On Tue, 24 May 2022 09:07:34 -0700 (PDT), John Walliker <jrwalliker@gmail.com> wrote:>On Tuesday, 24 May 2022 at 15:43:20 UTC+1, Phil Hobbs wrote: >> John Walliker wrote: > >> > Does anyone actually sell surface mount LND150s at the moment? All >> > the usual suppliers seem to be out of stock for at least several months. >> > >> > John >> > >> TO-92s are good for the soul. > >Maybe I should create a composite SOT-23/TO-92 footprint "just in case". >JohnJust put them in parallel on the schematic. -- If a man will begin with certainties, he shall end with doubts, but if he will be content to begin with doubts he shall end in certainties. Francis Bacon
Reply by ●May 24, 20222022-05-24
jlarkin@highlandsniptechnology.com wrote:> On Tue, 24 May 2022 10:43:08 -0400, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> John Walliker wrote: >>> On Tuesday, 24 May 2022 at 09:08:21 UTC+1, whit3rd wrote: >>>> On Monday, May 23, 2022 at 3:29:10 PM UTC-7, John Larkin wrote: >>>>> On Mon, 23 May 2022 11:06:00 -0700 (PDT), whit3rd <whi...@gmail.com> >>>>> wrote: >>>>>> On Monday, May 23, 2022 at 10:19:30 AM UTC-7, John Larkin wrote: >>>>>> >>>>>>> I want an LED blinker to show that a high-voltage power supply is >>>>>>> still dangerous. It should discharge the supply at some low current >>>>>>> and blink from, say, 1400 volts down to maybe 40. >>>>>> >>>>>> So, a series string of fifteen current-limit diodes running a capacitor- >>>>>> diac-LED blinkielight? S-272 seems suitable >>>>>> >>>>>> <https://www.mouser.com/datasheet/2/362/P22-23-CRD-1729293.pdf> >>>>> The Supertex LND150 is a 500 volt depletion fet. A source resistor >>>>> will program the current, and they can apparently be strung in series >>>>> without problems. >>>> Yeah, and a 'current-limit diode' is also a depletion FET. With a zener >>>> limit specified (I'm not sure about LND150). Multiples only share >>>> the voltage with such a matching zener specification. >>>> >>>> A resistor would work, too, but the alarm blinkie would change frequency >>>> dramatically. >>> >>> Does anyone actually sell surface mount LND150s at the moment? All >>> the usual suppliers seem to be out of stock for at least several months. >>> >>> John >>> >> TO-92s are good for the soul. > > Rarely! But we're using a TO-92 LM35 to measure the temp of a CPU > cooler that we're using as a mosfet heat sink. We'll glue it to the > side of the cooler and plug it into three little pin sockets. > >> >> Cheers >> >> Phil Hobbs >> >> (Who just designed one into a supply-dictated board spin.) :( > > Are TO-92s easier to get than surfmount parts? At least it's an > option.Some of them. 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 ●May 24, 20222022-05-24
jlarkin@highlandsniptechnology.com wrote:> On Tue, 24 May 2022 10:08:29 -0400, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> John Larkin wrote: >>> On Mon, 23 May 2022 11:06:00 -0700 (PDT), whit3rd <whit3rd@gmail.com> >>> wrote: >>> >>>> On Monday, May 23, 2022 at 10:19:30 AM UTC-7, John Larkin wrote: >>>> >>>>> I want an LED blinker to show that a high-voltage power supply is >>>>> still dangerous. It should discharge the supply at some low current >>>>> and blink from, say, 1400 volts down to maybe 40. >>>> >>>> So, a series string of fifteen current-limit diodes running a capacitor- >>>> diac-LED blinkielight? S-272 seems suitable >>>> >>>> <https://www.mouser.com/datasheet/2/362/P22-23-CRD-1729293.pdf> >>> >>> The Supertex LND150 is a 500 volt depletion fet. A source resistor >>> will program the current, and they can apparently be strung in series >>> without problems. >>> >>> Three of them would do. They are around 30 cents each. >>> >>> A spin on Piglet's circuit might to the blinker. >>> >> >> I'd probably be happier with a gate bias string to force the voltages to >> equalize. Of course the resistors would have to be physically quite >> large to take the voltage. >>> > Somebody told me (was it you?) that they are OK in series. One or two > may avalanche somewhere above 500 volts and one will actually regulate > the current. I'm talking 50 or 100 uA in my case. > > >I've never used them above about 250V. 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 ●May 24, 20222022-05-24
On Tue, 24 May 2022 16:47:30 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>jlarkin@highlandsniptechnology.com wrote: >> On Tue, 24 May 2022 10:08:29 -0400, Phil Hobbs >> <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >>> John Larkin wrote: >>>> On Mon, 23 May 2022 11:06:00 -0700 (PDT), whit3rd <whit3rd@gmail.com> >>>> wrote: >>>> >>>>> On Monday, May 23, 2022 at 10:19:30 AM UTC-7, John Larkin wrote: >>>>> >>>>>> I want an LED blinker to show that a high-voltage power supply is >>>>>> still dangerous. It should discharge the supply at some low current >>>>>> and blink from, say, 1400 volts down to maybe 40. >>>>> >>>>> So, a series string of fifteen current-limit diodes running a capacitor- >>>>> diac-LED blinkielight? S-272 seems suitable >>>>> >>>>> <https://www.mouser.com/datasheet/2/362/P22-23-CRD-1729293.pdf> >>>> >>>> The Supertex LND150 is a 500 volt depletion fet. A source resistor >>>> will program the current, and they can apparently be strung in series >>>> without problems. >>>> >>>> Three of them would do. They are around 30 cents each. >>>> >>>> A spin on Piglet's circuit might to the blinker. >>>> >>> >>> I'd probably be happier with a gate bias string to force the voltages to >>> equalize. Of course the resistors would have to be physically quite >>> large to take the voltage. >>> > >> >> Somebody told me (was it you?) that they are OK in series. One or two >> may avalanche somewhere above 500 volts and one will actually regulate >> the current. I'm talking 50 or 100 uA in my case. >> >> >> >I've never used them above about 250V. > >Cheers > >Phil HobbsI tested one. It avalanches at 620 volts, no damage at low current. The gate zeners at about +-40, again no damage. -- Anybody can count to one. - Robert Widlar
Reply by ●May 25, 20222022-05-25
On 22/05/2022 7:32 pm, Piotr Wyderski wrote:> piglet wrote: > >> To make an oscillator a discrete design with high value series >> resistors might be better, this draws an average 10nA to make narrow >> pulses every 8-9 secs... > > After some prototyping I can confirm, your UJT-emulating circuit wins > hands down. I removed R6, R2, Q3 and R5, changed C1 and C2 to 470p and > coupled to the C2 discharge energy via a small transformer, getting > beautiful 1us spikes @28Hz. Thank you, Piglet! > > Best regards, Piotr > >You are very welcome, always pleased when a dirt cheap descrete circuit still beats the world. It is not my design, the complementary series multivibrator has been around since the 1960s. piglet
Reply by ●May 25, 20222022-05-25
On 23/05/2022 11:28 pm, John Larkin wrote:> On Mon, 23 May 2022 11:06:00 -0700 (PDT), whit3rd <whit3rd@gmail.com> > wrote: > >> On Monday, May 23, 2022 at 10:19:30 AM UTC-7, John Larkin wrote: >> >>> I want an LED blinker to show that a high-voltage power supply is >>> still dangerous. It should discharge the supply at some low current >>> and blink from, say, 1400 volts down to maybe 40. >> >> So, a series string of fifteen current-limit diodes running a capacitor- >> diac-LED blinkielight? S-272 seems suitable >> >> <https://www.mouser.com/datasheet/2/362/P22-23-CRD-1729293.pdf> > > The Supertex LND150 is a 500 volt depletion fet. A source resistor > will program the current, and they can apparently be strung in series > without problems. > > Three of them would do. They are around 30 cents each. > > A spin on Piglet's circuit might to the blinker. >My preference would be to skip the depletion fets and just use dropper resistors - cheaper, more reliable, and best of all the non constant blink rate gives a good visual confirmation that the HV capacitor is actually discharging. Blinking could be as simple as a diac or bjt used as negistor. Spice won't model E-B breakdown and reverse beta so can't simulate negistor operation but breadboarding would be very quick. piglet
Reply by ●May 25, 20222022-05-25
piglet wrote:> You are very welcome, always pleased when a dirt cheap descrete circuit > still beats the world. It is not my design, the complementary series > multivibrator has been around since the 1960s.This is how it looks now. L1 and L3 pump the flyback core, L3 boosts the voltage of the core reset pulse to 600mV+, even at 1.2V_IN, R5 steals that pulse (or not), Q3 detects if there was the pulse, C3/Q4 is a zero-power monostable (assuming there are no pulses from Q3) and M1 makes that information accessible to the external world. It is shocking how simple it is and how well it works. Best regards, Piotr Version 4 SHEET 1 2136 1236 WIRE 416 -176 176 -176 WIRE 720 -176 416 -176 WIRE 1264 -176 720 -176 WIRE 1648 -176 1264 -176 WIRE 720 -128 720 -176 WIRE 416 -80 416 -176 WIRE 720 48 720 -48 WIRE 960 48 720 48 WIRE 960 64 960 48 WIRE 720 96 720 48 WIRE 416 144 416 0 WIRE 656 144 416 144 WIRE 960 160 960 144 WIRE 416 224 416 144 WIRE 720 272 720 192 WIRE 960 320 960 224 WIRE 960 320 784 320 WIRE 960 384 960 320 WIRE 176 528 176 -176 WIRE 416 576 416 288 WIRE 528 576 416 576 WIRE 2080 608 1904 608 WIRE 416 624 416 576 WIRE 528 624 528 576 WIRE 720 640 720 368 WIRE 2080 656 2080 608 WIRE 1904 736 1904 608 WIRE 176 752 176 608 WIRE 416 752 416 704 WIRE 416 752 176 752 WIRE 720 752 720 720 WIRE 720 752 416 752 WIRE 960 752 960 464 WIRE 960 752 720 752 WIRE 1264 768 1264 -176 WIRE 2080 768 2080 736 WIRE 176 784 176 752 WIRE 1648 816 1648 -176 WIRE 1264 864 1264 848 WIRE 1392 864 1392 784 WIRE 1392 864 1264 864 WIRE 1472 864 1392 864 WIRE 1584 864 1552 864 WIRE 1264 880 1264 864 WIRE 416 896 272 896 WIRE 1392 896 1392 864 WIRE 272 928 272 896 WIRE 528 928 528 704 WIRE 1056 928 528 928 WIRE 1200 928 1136 928 WIRE 1648 928 1648 912 WIRE 1776 928 1648 928 WIRE 1904 928 1904 816 WIRE 1648 944 1648 928 WIRE 1392 976 1392 960 WIRE 1072 992 1072 976 WIRE 416 1008 416 976 WIRE 1776 1008 1776 928 WIRE 1856 1008 1776 1008 WIRE 1264 1024 1264 976 WIRE 1120 1040 1120 976 WIRE 1648 1040 1648 1024 WIRE 1904 1040 1904 1024 WIRE 1120 1136 1120 1120 FLAG 176 784 0 FLAG 416 1008 0 FLAG 272 1040 0 FLAG 1264 1024 0 FLAG 1392 784 V_OUT FLAG 1648 1040 0 FLAG 1392 976 0 FLAG 1072 992 0 FLAG 1120 1136 0 FLAG 2080 768 0 FLAG 1904 1040 0 SYMBOL voltage 176 512 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value 3 SYMBOL pnp 784 368 R180 SYMATTR InstName Q1 SYMATTR Value BC557C SYMBOL npn 656 96 R0 SYMATTR InstName Q2 SYMATTR Value BC547C SYMBOL res 704 -144 R0 SYMATTR InstName R1 SYMATTR Value 10Meg SYMBOL res 944 368 R0 SYMATTR InstName R2 SYMATTR Value {R_OSC} SYMBOL res 400 -96 R0 SYMATTR InstName R3 SYMATTR Value {R_OSC} SYMBOL cap 400 224 R0 SYMATTR InstName C1 SYMATTR Value {C_OSC} SYMBOL cap 944 160 R0 SYMATTR InstName C2 SYMATTR Value {C_OSC} SYMBOL res 704 624 R0 SYMATTR InstName R4 SYMATTR Value 1m SYMBOL ind2 400 608 R0 WINDOW 0 -42 23 Left 2 WINDOW 3 -102 64 Left 2 SYMATTR InstName L1 SYMATTR Value {L_PRI} SYMATTR Type ind SYMATTR SpiceLine Cpar=0 SYMBOL ind2 400 880 R0 WINDOW 3 -55 -7 Left 2 SYMATTR Value {L_SENSE} SYMATTR InstName L2 SYMATTR Type ind SYMBOL ind2 544 720 R180 WINDOW 0 -41 86 Left 2 WINDOW 3 -111 59 Left 2 SYMATTR InstName L3 SYMATTR Value {L_SEC} SYMATTR Type ind SYMATTR SpiceLine Cpar=0 SYMBOL res 256 912 R0 SYMATTR InstName R5 SYMATTR Value 33 SYMBOL ind2 944 48 R0 SYMATTR InstName L4 SYMATTR Value {L_PRI} SYMATTR Type ind SYMBOL npn 1200 880 R0 SYMATTR InstName Q3 SYMATTR Value BC547C SYMBOL res 1248 752 R0 SYMATTR InstName R6 SYMATTR Value 10Meg SYMBOL pnp 1584 912 M180 SYMATTR InstName Q4 SYMATTR Value BC557C SYMBOL res 1568 848 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R7 SYMATTR Value 1Meg SYMBOL res 1632 928 R0 WINDOW 0 -56 28 Left 2 WINDOW 3 -91 53 Left 2 SYMATTR InstName R8 SYMATTR Value 10Meg SYMBOL cap 1376 896 R0 SYMATTR InstName C3 SYMATTR Value 33n SYMBOL sw 1040 928 R270 SYMATTR InstName S1 SYMATTR Value MYSW SYMBOL voltage 1120 1024 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V2 SYMATTR Value PULSE(0 1 300m 10n 10n 300m 1) SYMBOL res 1888 720 R0 SYMATTR InstName R10 SYMATTR Value 1000 SYMBOL voltage 2080 640 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V3 SYMATTR Value 12 SYMBOL nmos 1856 928 R0 SYMATTR InstName M1 SYMATTR Value BSS123 TEXT 216 -368 Left 2 !.param C_OSC=470p TEXT 216 -344 Left 2 !.param R_OSC=100Meg TEXT 560 -424 Left 2 !.param AL=5000n TEXT 560 -400 Left 2 !.param N_PRI=26 TEXT 560 -376 Left 2 !.param N_SEC={N_PRI*4} TEXT 560 -352 Left 2 !.param N_SENSE=8 TEXT 560 -320 Left 2 !.param L_PRI={N_PRI*N_PRI*AL} TEXT 560 -296 Left 2 !.param L_SEC={N_SEC*N_SEC*AL} TEXT 560 -272 Left 2 !.param L_SENSE={N_SENSE*N_SENSE*AL} TEXT 240 800 Left 2 !K L1 L2 L3 L4 0.995 TEXT 144 1048 Left 2 !.tran 1 TEXT 912 -376 Left 2 ;PRI/SEC: twisted 6x26 DNE0.2mm @ 10mm OD ring F938. TEXT 912 -352 Left 2 ;SENSE: TIW!!! TEXT 1376 1048 Left 2 !.ic V(V_OUT)=0 TEXT 1008 1192 Left 2 !.model MYSW SW(Ron=1m Roff=1G Vt=.5 Vh=-.4)
