WAYNE CHIRNSIDE wrote in a message to ROY J. TELLASON:

-=> ROY J. TELLASON wrote to WAYNE CHIRNSIDE <=-

 RJT> Yes,  I think perhaps my earlier attempt at messing with those (or
 RJT> maybe it was 4016s) went poorly because I didn't bias them,  or run
 RJT> them off a split supply.
 RJT>  I've got a little circuit here that's a charge pump to give you a
 RJT> little bit of -5V from a +5V supply -- I'll bet that would do the trick
 RJT> and if I feed it unregulated voltage then I could probably have pretty
 RJT> stable dual 5V supplies, which should be more than adequate for
 RJT> line-level audio signals.

 RJT> I wasn't thinking of switching in bunches of different resistors to do
 RJT> gain control,  but rather some sort of pulse-width modulation.  Just
 RJT> gotta pick a high enough frequency and figure out what sort of
 RJT> filtering needs to be at the output end of things to make this work.

 WC> Sounds like you might be attempting some sort of single bit
 WC> power amplifier?

It was some time ago that I was playing with this idea,  so it's hard to
recollect exactly what it was I had in mind.  Something like digital volume
controls without the need for A/D and D/A conversions,  I think.  That'd
give me the ability to do a *lot* of stuff.

 WC> Wish I had the circuit for a negative resistance pulser by Forrest
 WC> Mims I once had from Popular Electronics.

 RJT> He sure published an awful lot of stuff.  And much of it is in those
 RJT> little books that you can get at radio shack,  maybe that circuit is in
 RJT> there?

 WC>  Perhaps I'll look.

I know at one point they had this "engineer's notebook" but
apparently some time back they then split them up into a whole series of
them.  More money to be made from a bunch of smaller books,  I guess.

 WC> Would like to pulse some white LEDs I've got now.

 RJT> I have yet to get a hold of any of those,  or any blue ones.

 WC> No blue ones here either yet but the packaging is the same for both
 WC> types so it tells you the cell types for both.

Ah.

 WC> I don't see myself replacing individual cells when the
 WC> whole package is cheaper.

This one grandkid got this bit of cheap jewelry that flashes a blue one, 
I'll have to ask her if it's still working...

 WC> White LEDs are available from the local Radio Shack for 4.95 each

 RJT> That's a pretty hefty price,  and I don't remember seeing them there,
 RJT> but that's no surprise as I haven't spent that much time in there in
 RJT> recent years anyhow,  and they typically charge more than most places
 RJT> for some stuff.

 WC>  I haven't been there in years either but checked the web site to 
 WC> find the info.

Oh.  Checking their web site never occurred to me.  

 WC>  I'd expect you could buy a bunch cheaper mail order at someplace 
 WC> like DigiKey or Matt Electronics.

Yeah.

 WC>  I've both PDF catalogs here and DigiKey's is a bear to read but
 WC> Matt Electronics is easy.

I was thinking about calling Digikey and asking them to send me out one on
paper,  like they used to.  Dunno Matt Electronics.  I'm not real hot on
suppliers at this point anyhow,  being more bugged by the fact that I've
accumulated all these parts for years now and haven't done all that much
with them.

My last Radio Shack purchase was a few boards to build stuff on,  and some
terminals,  which I envision a use for on one project.

 WC> or you can get the same thing in a battery operated keychain light
 WC> at Walgreens for 1.50 along with 2 3 volt lithium 2016 coin cells.

 RJT> Too bad we don't have any of those around here.

 WC>  Perhaps they can be found in some other discount or drugstore. 
 WC> Found mine as an impulse buy item right at the checkout.

Maybe when I get out some time,  which I'm not doing too much these days. 
I started getting active again in the job search today,  so things will
probably change.  I'll be out more,  busier,  and have less time to mess
with stuff...

 WC> The white LED has full length leads with the typical anode longer
 WC> arrangement, the white ones have the 2 2016 cells which fit my
 WC> watch and the blue ones have 1 2032 which fits my computer CMOS
 WC> cell holders :-)

 RJT> Do the white ones take more voltage to operate,  then?

 WC> Radio Shack lists theirs at 3.6 volts and I suspect they're
 WC> identical, same package style anyway, 20 MA. Max.

A bit more than what you could get out of one 3V coin cell,  then.

 WC> I'm guessing given the monochromatic nature of LEDs that the white
 WC> LED is actually an ultra-violet LED illuminating a phospher much 
 WC> like UV illuminates a phospher in a flourescent.

Maybe,  I don't have a clue.  I stopped trying to keep up with things some
time back,  and there are some serious gaps in my understanding of what's
going on with a lot of the technology these days.  At least I have web
access now,  and can look for the info when I happen to think of it while
online.

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