Dropping a few tenths of a volt problem

On a sunny day (Fri, 21 Mar 2014 17:08:42 +0100) it happened Cursitor Doom wrote in :

Not exactly, ONE PIC DOES ALL.

you could HEAR that nuke?

On a sunny day (Fri, 21 Mar 2014 17:11:01 +0100) it happened Cursitor Doom wrote in :

So?

in o----->|-----o---o--------o out 1n4148 | | .-. | | | --- 10k | | --- 100n '-' | | | === === GND GND

This should stretch brief clicks nicely, without needing any of that hifalutin integrated circuit crap.

I don't have a PIC to hand and neither do I care to re-learn PIC programming for what should be a simple fix!!!

Didn't buy this thing for nucular war; just for checking canned seafood.

For what it's worth, I have surface mount Schottkeys here that measure 80mV forward voltage. Quite leaky in the reverse, if that matters.

On a sunny day (Fri, 21 Mar 2014 17:41:52 +0100) it happened Cursitor Doom wrote in :

If it shines in the dark stay clear of it! Photocell?

Computer says no. Simulation suggests this will just tail the pulses off. They might be a bit thicker at the 'base' as it were, but for this to work it would still have to be fed into a Schmitt or something similar.

Don't you have some sort of current source driving the zener, rather than a voltage source?

Is the zener just for protection?

It would appear that Panteltje is on the right track. Just protect that NPN and then drive your logic. ...Jim Thompson

No, he's getting hungry.

Describe your pulses. I presume they are currents? ...Jim Thompson

I'm just trying to represent the waveform I see on my analog storage scope as closely as possible that LTspice will allow. The real-world pulses the GC generates for the earpiece socket are not very uniform. They're *very* thin and spikey; too fast for a moving coil speaker to react to, I would guess. Plus they vary in amplitude from a few volts to over a dozen.

That's the principal purpose for it, yes. It might not be necessary, but I thought it best to try to protect the Schmitt input.

I'll take a closer look at what he's suggested in that respect.

Please see Message-ID: for a description.

It's worked well for me in the past, to solve a similar problem.

I didn't use a computer to fool me into thinking it'd work or not -- I actually built it and tried it out. That must have been my mistake.

You say "volts". Source impedance or how measured?

Maximum observed voltage, minimum voltage you want detected?

Rough idea of pulse width, repetition rate? ...Jim Thompson

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ve

I have several little flashlights that use a single AA cell to drive a wh ite LED. There's a voltage upconverter between the cell and the LED that's the same diameter as the cell, and about 1/4 inch long. Cost, under US$1.00 each. I bought several of them just to scavenge the upconverter out of for other purposes because I can't buy/design anything better that small.

Mark L. Fergerson

Your simulation does not match any real component: The gates output only 1.0 V signal, which is not too good for the next stages.

How long is a string?

Yes, I know, which is why I stated more than once that I'm posting these as schematics only and not for simulation purposes!

Indeed! It's next to impossible for me to measure, Jim. I can't display the pulses at all on my conventional scopes; I've had to resort to an old analog storage job (bw 18Mhz!) for the purpose and it's really not capable of fully resolving these pulses, which are extremely short-lived and resemble transient spikes more than a 'pulse' as such. I'm well aware that it's a very unsatisfactory state of affairs not knowing the full characterists of the signal I'm dealing with, but there's not a lot I can do about it. I have recently acquired a fancy 100Mhz digital storage scope but the controls are totally unfamiliar and I have yet to get to grips with it so that's not a lot of use either at present...