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From: Robert Baer
X-Mailer: Mozilla 4.75 [en] (Win98; U)
Subject: Re: design help please
Date: Fri, 01 Nov 2002 04:00:55 GMT
NNTP-Posting-Date: Thu, 31 Oct 2002 20:00:55 PST
Organization: EarthLink Inc. -- http://www.EarthLink.net
David Jones wrote:
> I'd like to design a cricuit with the following characteristics. It needs
> to be very small, I need to be able to have 5 different outputs,which would
> be five different pairs of wires(+ and -) that I could connect to something
> else. I need to be able to program that circuit to send electricity to those
> different terminals at different dc(on off) frequencies, all independent of
> each other. I also need to be able to tell the circuit to provide
> electricity to each individual terminal at the desired frequency for a
> certain amount of time(say 1/20 of a second to 10 seconds). Can someone
> give me an outline of what I should think about using. I'm a beginner to
> electronics so I also have to study new electronic concepts. Any advice on
> what I should look into such as programmable microprocessors(which I know
> nothing about at the moment) or mosfets or what. And how can I make it
> extremely small? Is it possible to make your own integrated circuits even
> if they are much larger than typical IC's? and be able to do so at a
> reasonable price?
Making your own IC is not cost effective, even if you *own* a fab
shop, or hire a fab shop unless quantities are in the hundreds or more.
1) Start with a programmable oscillator (there is an SOIC that uses a
resistor for setting frequency of the square wave output) and use a
multiplexor for directing the signal to a given output. This only needs
2 ICs and has the disadvantages of (a) square wave output instead of
sinewave, (b) only one output can be activated at a time, and (c)
control is remote (off board).
2) Use an 8-bit microcontroller; only one IC for generator and control
to outputs. This only needs 1 IC and has the disadvantages of (a) square
wave output instead of sinewave, (b) control is a "fixed" program.
In both cases, the output is single ended; a logic inverter (another
IC for up to 10 lines) would then give a differential signal.
In both cases, the board space is a few square inches, low profile.
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