Freeware or low cost schematic software?

Mar 21, 2005 24 Replies

Here's why I'm asking. When I heard the software could do SPICE, I thought it would be fun to model a crystal radio detector, using a germanium diode.

So I'd need to model a radio signal source, which I'm not sure how to do with this, and a loop antenna, which I'm not sure how to do, then put that into the diode and feed the cathode down into a resistor with a small capacitor to detect it into audio. I don't get the impression that this kind of software is made for that.

Yours In Liberty, Melissa - Colorado, U.S.A. http://melissasliberty.blogspot.com/ The last best hope for liberty, to give the world its first Bill of Rights: http://www.UPAlliance.org/billofrights.htm

I read in sci.electronics.design that Melissa wrote (in ) about 'Freeware or low cost schematic software?', on Wed, 23 Mar 2005:

Just a sine-wave voltage source of, say 1 mV, frequency 1 MHz

If it's untuned, a 100 uH or so inductor in series with the voltage generator. If it's tuned, you need to know the L and C values, and put that parallel-tuned circuit in series with your voltage generator. You need to add some resistance in series with the inductor, otherwise Splice will barf at the infinite Q. The resistance wants to be about

1/100th of the inductive reactance.

Yes, it will do that quite well, but with a sine-wave input you will only get DC out, of course. To get modulation, you need to read the application documentation to find out how to model an amplitude-modulated voltage generator by using a voltage generator at modulation frequency (such as 1 kHz) feeding a voltage-controlled voltage source (VCVS) running at 1 MHz.

Regards, John Woodgate, OOO - Own Opinions Only. There are two sides to every question, except 'What is a Moebius strip?' http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

You could try something along these lines:

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In CircuitMaker I used two sine waves,one of 1 kHz and the other (to keep simulation times short) of 100 kHz. I'm sure others will suggest a better way of 'combining' them, but that somewhat arbitrary choice of mine seems to work. Amplitudes and RF frequency could of course be altered to suit your crystal circuit simulation.

Terry Pinnell Hobbyist, West Sussex, UK

Sounds too complicated for me to mess with.

It's probably best just to do T&E breadboarding with this.

What I'd actually like to do, is set up a loop and tune it to 60 Hz and see if I can get enough local power line energy to run an LED with it. We have high lines about a block away, and power lines running around the house too, so I suspect I can.

Yours In Liberty, Melissa - Colorado, U.S.A. http://melissasliberty.blogspot.com/ The last best hope for liberty, to give the world its first Bill of Rights: http://www.UPAlliance.org/billofrights.htm

I read in sci.electronics.design that Melissa wrote (in ) about 'Freeware or low cost schematic software?', on Thu, 24 Mar 2005:

That would have to be a loop with LOT of turns, even if you resonate it with a farad.

Regards, John Woodgate, OOO - Own Opinions Only. There are two sides to every question, except 'What is a Moebius strip?' http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

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