Hi Les/ T.C

        I looked at the circuit drawing but I will be very surprised if you
get a steady output from the 7805 regulator.  tell me what you are trying to
do?


nash


-----Original Message-----
From: T.C. Phelps [mailto:tcphelps@YAHOO.COM]
Sent: 12 August 2002 20:56
To: PICLIST@MITVMA.MIT.EDU
Subject: [EE]: Membrane latching power switch for PIC circuit


 Hi Les,

>I DID read Horowitz & Hill Art of Electronics
>(transistor section) before I posted the question,
>but I find it heavy going.  I need to find a book
>which explains things in more basic terms -

"BJT's for dummies" would have been a great help when
I took the semiconductor devices course!

I have Microelectronic Circuits by Sedra/Smith which
is not -too- bad, provided you read the applications
section and not the theory section; if I can
understand it, then anyone can :).

>So, if I understand your response Todd et al, that
>means I can drive the base of a PNP BJT with the
> collector of a NPN , the emitter of which goes to
>ground, and the base of which will connect to my PIC
>pin - rather like the circuit that Rick C posted on
>this thread, and Matt Pobursky pointed out?

I couldn't view the circuits they sent (Digest only
gives the ASCII translation) but here's an "off the
top of my head" schematic. I'm only suggesting that
something _like_ this may work for you (hence the lack
of component values); I haven't analyzed or simulated
it so you'd have to check it, maybe fix a bug or two,
<insert standard legal disclaimer here> ... :)

> PS So my circuit has +9v at the collector, +4.4V at
>the emitter...have I invented a logic controlled 4.6v

>heater? :o)

Probably; Just be glad it is only 9V and not 200 or
so; T'is better to curse the darkness than
accidentally set fire to your workbench. ;)

Regards,
Todd



He who said the perpetual motion machine was
impossible obviously never tried to debug an unwanted
infinite loop in MPLAB.





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