On Thu, 26 May 2022 18:06:43 +0200, Piotr Wyderski
<bombald@protonmail.com> wrote:
>jlarkin@highlandsniptechnology.com wrote:
>
>> The 1400v supply is low current and doesn't store lethal energy
>
>Oh, in that case never mind. My comment was entirely safety-driven.
>
>> Sometimes we do things just because they are cool.
>
>So do I. :)
>
>> We also use DN2530, a 300 v depl fet in SOT89. It good for discharging
>> bigger caps.
>
>I use it as a resettable fuse. The short-circit current is limited and
>the part just stops being hot when the short-circuit is removed. The
>carbon-based PTCs wear off.
>
> Best regards, Piotr
>
Ixys makes a self-protecting SSR, CPC1540. Off leakage is picoamps.
If you drive the input full-time, it becomes a fuse.
--
Anybody can count to one.
- Robert Widlar
Reply by Piotr Wyderski●May 26, 20222022-05-26
jlarkin@highlandsniptechnology.com wrote:
> The 1400v supply is low current and doesn't store lethal energy
Oh, in that case never mind. My comment was entirely safety-driven.
> Sometimes we do things just because they are cool.
So do I. :)
> We also use DN2530, a 300 v depl fet in SOT89. It good for discharging
> bigger caps.
I use it as a resettable fuse. The short-circit current is limited and
the part just stops being hot when the short-circuit is removed. The
carbon-based PTCs wear off.
Best regards, Piotr
Reply by ●May 26, 20222022-05-26
On Thu, 26 May 2022 07:51:28 +0200, Piotr Wyderski
<bombald@protonmail.com> wrote:
>jlarkin@highlandsniptechnology.com wrote:
>
>> Had a part in mind? If it's enhancement mode, it will need something
>> to bias it up.
>>
>> We do have the LND150s in stock, SOT23 package.
>
>Mouser has this IXTA1N170DHV. More expensive that LND150, but I am not
>sure if a safety circuit is the best place for savings and IIRC your
>business is of the high-added-value/low volume profile anyway. Just
>saying, it's your decision.
The 1400v supply is low current and doesn't store lethal energy, but
someone could damage parts by poking around while there's still
voltage. The linear discharge with blinker helps with that, and is
cool too. Sometimes we do things just because they are cool.
>
>I use the IXTA08N100D2HV for the same purpose (have a blinker too, and a
>buzzer specifically tuned to emulate a fighter jet warning system:
>https://youtu.be/fd50GtnXR7Y?t=1145, just couldn't resist), but my cap
>voltage is under 900V, 650V typical.
>
> Best regards, Piotr
That is an interesting part, but Mouser has four for $20 each. That's
another factor these days, availability and price.
We also use DN2530, a 300 v depl fet in SOT89. It good for discharging
bigger caps.
In a couple of boxes with gigantic caps, we used a depletion fet + LED
indicator and a discharge resistor + pushbutton inside, so our techs
are warned and didn't have to wait minutes to poke around.
--
Anybody can count to one.
- Robert Widlar
Reply by Piotr Wyderski●May 26, 20222022-05-26
jlarkin@highlandsniptechnology.com wrote:
> Had a part in mind? If it's enhancement mode, it will need something
> to bias it up.
>
> We do have the LND150s in stock, SOT23 package.
Mouser has this IXTA1N170DHV. More expensive that LND150, but I am not
sure if a safety circuit is the best place for savings and IIRC your
business is of the high-added-value/low volume profile anyway. Just
saying, it's your decision.
I use the IXTA08N100D2HV for the same purpose (have a blinker too, and a
buzzer specifically tuned to emulate a fighter jet warning system:
https://youtu.be/fd50GtnXR7Y?t=1145, just couldn't resist), but my cap
voltage is under 900V, 650V typical.
Best regards, Piotr
Reply by ●May 25, 20222022-05-25
On Wed, 25 May 2022 20:31:12 +0200, Piotr Wyderski
<bombald@protonmail.com> wrote:
>John Larkin wrote:
>
>> The simple version, 3x57a with LND150s would be fine for a 1400 volt
>> LED blinker.
>
>Why wouldn't you just use a 1.7kV+ rated DMOS?
>
> Best regards, Piotr
Had a part in mind? If it's enhancement mode, it will need something
to bias it up.
We do have the LND150s in stock, SOT23 package.
--
Anybody can count to one.
- Robert Widlar
Reply by Piotr Wyderski●May 25, 20222022-05-25
John Larkin wrote:
> The simple version, 3x57a with LND150s would be fine for a 1400 volt
> LED blinker.
Why wouldn't you just use a 1.7kV+ rated DMOS?
Best regards, Piotr
Reply by John Larkin●May 25, 20222022-05-25
On Wed, 25 May 2022 09:22:48 -0700 (PDT), "ke...@kjwdesigns.com"
<keith@kjwdesigns.com> wrote:
>On Wednesday, 25 May 2022 at 06:41:00 UTC-7, Phil Hobbs wrote:
>...
>> >>> 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.
>> > I tested one. It avalanches at 620 volts, no damage at low current.
>> >
>> > The gate zeners at about +-40, again no damage.
>> Yabbut, at 1400V at least one and probably two of them will be
>> continuously avalanching during normal operation, unless the drain
>> curves are squishy enough to take up the unit-to-unit spread in I_DSS.
>> (Maybe they are.) That would take a lot of testing to confirm as safe.
>>
>> The avalanche voltage increases with temperature, so there'd be no
>> automatic sharing of dissipation.
>...
>
>The Art of Electronics - The X Chapters. depicts that configuration and variants with a discussion in section 3.x.6.5
>
>The simple configuration with just source resistors can have steps in the current as the voltage is varied as each device in turn avalanches.
>
>kw
The simple version, 3x57a with LND150s would be fine for a 1400 volt
LED blinker. And there are some diacs that would work for the periodic
cap discharge into the LED. 9 or so parts total.
--
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 ke.....@kjwdesigns.com●May 25, 20222022-05-25
On Wednesday, 25 May 2022 at 06:41:00 UTC-7, Phil Hobbs wrote:
...
> >>> 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.
> > I tested one. It avalanches at 620 volts, no damage at low current.
> >
> > The gate zeners at about +-40, again no damage.
> Yabbut, at 1400V at least one and probably two of them will be
> continuously avalanching during normal operation, unless the drain
> curves are squishy enough to take up the unit-to-unit spread in I_DSS.
> (Maybe they are.) That would take a lot of testing to confirm as safe.
>
> The avalanche voltage increases with temperature, so there'd be no
> automatic sharing of dissipation.
...
The Art of Electronics - The X Chapters. depicts that configuration and variants with a discussion in section 3.x.6.5
The simple configuration with just source resistors can have steps in the current as the voltage is varied as each device in turn avalanches.
kw
Reply by Phil Hobbs●May 25, 20222022-05-25
jlarkin@highlandsniptechnology.com wrote:
> On Wed, 25 May 2022 09:40:48 -0400, Phil Hobbs
> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>
>> jlarkin@highlandsniptechnology.com wrote:
>>> 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.
>>
>>> I tested one. It avalanches at 620 volts, no damage at low current.
>>>
>>> The gate zeners at about +-40, again no damage.
>>
>> Yabbut, at 1400V at least one and probably two of them will be
>> continuously avalanching during normal operation, unless the drain
>> curves are squishy enough to take up the unit-to-unit spread in I_DSS.
>> (Maybe they are.) That would take a lot of testing to confirm as safe.
>>
>> The avalanche voltage increases with temperature, so there'd be no
>> automatic sharing of dissipation.
>
> If two avalanche at about 650 volts each, that runs the third one as
> the current limiter, at roughly 100 volts. Seems like it just works.
>
> At 100 uA, the two that avalanche dissipate maybe 65 mW each. The
> linear one is necessarily less.
Provided that there's no long-term damage mechanism. It's going to be
in that state for a long long time.
> Now I need a good blinker circuit.
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.nethttp://hobbs-eo.com
Reply by ●May 25, 20222022-05-25
On Wed, 25 May 2022 11:21:22 +0100, piglet <erichpwagner@hotmail.com>
wrote:
>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.
The discharge would be a slow exponential and the blink rate would
approach zero towards the end. Neither sounds good to me.
>
>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