LED driver

To the top of the reservoir cap:

HV RAIL | \ / 3M \ / | o--------o--------------------------------------o--------o-------' | | | | | | | \ | | | | / | | | | \ RLED | | \ | / | | / 18M | | | | \ | | | / | 4.7M | | | | | V -> | | o--------)-------------/\/\-----------| - | | | | | | LED | | | | |-------------------| | | | | | |/ | | | . | | o------| | | | | | | | |> | | | ||-+ | | | | | IN OUT | | ||>>

Same in my case. I just came from overseas and had no ski equipment or anything resembling suitable clothing with me. I was in a T-shirt and jeans. The boots and skis were rented. No helmet, and that still gives me goose bumps, I'd never do that again.

This pair of jeans was pretty much hosed after that day.

can hang.

something better

V,

That could be an interesting widget if you can make it. I would like to see your first cut at it. My initial analysis says doable but too challenging for me to be fun.

?-)

Updated with some extra waveforms.

Can anyone tell me why C2 and R3 are there? ...Jim Thompson

I'd guess C2 is to provide an initial low load impedance to the PUT so it latches on nice and fast?

I'd guess R3 is to limit PUT current into the LED driver/limiter. Without it the main reservoir C1 would discharge thru Q2, Q1 and Q4 without ever getting to light the LED?

piglet

Yes. And the requirement for the capacitive load on the PNPN creates the latch hazard.

Congratulations! Too short a blink, for sure!

More precisely, C2 is there because the added (current-limiting) R3 causes an instantaneous voltage drop which would impede the latching (because it would reduce voltage across latch when it's trying to draw current).

Update...

VoltageIndicator(SED).pdf

on the S.E.D/Schematics page of my website has been further updated to address "holding current hysteria" >:-}

If Larkin could prove a holding current issue he'd demonstrate it in a blink (pun intended :-), because he lives to denigrate me at every turn. But, when it comes to device-level design he fails miserably. ...Jim Thompson

Wrong again >:-} ...Jim Thompson

You terminated this thread!

Your killfile skills are really, really bad.

I would, if you hadn't terminated the thread.

You apparently so dense you don't know the difference between a thread and a SUBthread >:-}

Prove the hang or STFU. Piglet got it right... why can't you? ...Jim Thompson

Green baloney >:-} ...Jim Thompson

Put up an LT Spice asc file. It's too much work to enter this myself, just to once again prove an old geezer wrong.

I figured you'd weasel out, you always do... claim anything, but never actually prove it.

I disproved your claim myself... see my website...

VoltageIndicator(SED).pdf

on the S.E.D/Schematics page of my website has been further updated to address "holding current hysteria" >:-} ...Jim Thompson

Probably not. Discharging C1 hard into a decent LED would make a fat blink.

Exactly. That's why it has a lockup state. If C2 ever misses, for any reason, the PNPN pair won't unlatch. Negative feedback from Q4 and then Q6 fine-tunes the PNPN current to keep it locked.

Remove C2 and play with it. You should be able to find the latch states.

More and more green baloney. ...Jim Thompson

This subthread has been terminated due to lack of informative content.

ALL responses will be automatically deleted by Agent's filtering system.

Don't be silly. You can't stand to think that people are saying things about you that you can't see. None of your scores of claims about killfiling were ever true.

You've killfiled me, and all followups to me, maybe 30 times so far.

You just declare "killfile" when you don't want to face things. Bad engineering.

And it does have a latch state.

He certainly got it right: you need C2 to make it work. Which is why it has a static latch state.

Man! You are totally ignorant. You have it completely backwards. Dumb-diddly-dumb-dumb >:-}

Unbelievable!

Check with piglet. He'll be happy, I'm sure, to explain it to you.

Incredible that you can be THAT stupid. ...Jim Thompson

This subthread has been terminated due to lack of informative content.

ALL responses will be automatically deleted by Agent's filtering system.

The LED will only blink if its Vf is lower than Q4Vbe+ Q2Vbe+Q1Vcesat (or Q1Vbe+Q2Vbesat) or roughly 1.4V so an IRED possibly but not a visible LED - so R3 has to be there.

piglet