Freeware or low cost schematic software?

[Terry Pinnell]

Melissa <melissa@colorado.xxx> wrote:

John Woodgate <jmw@jmwa.demon.contraspam.yuk> wrote :

I read in sci.electronics.design that Melissa <melissa@colorado.xxx
wrote (in <q-ydnRvvEPgOWt3fRVn-qQ@forethought.net&gt about 'Freeware or
low cost schematic software?', on Tue, 22 Mar 2005:

Can you create a germanium diode with a .3V forward voltage drop?

Yes, but to understand how the model works, you first need to understand
that diodes don't actually have a 'threshold voltage' of 0.3 V for
germanium or 0.6 V for silicon. The relationship between current and
voltage is exponential (plus the effect of some series resistance), so
it looks the same whatever scale you look at it on. The 0.3 V and 0.6 V
come from the fact that those voltages apply for smallish practical
currents, e.g. 1 mA to 10 mA. The models, however, use the 'exponential
voltage-controlled current source in series with a resistor'
interpretation.


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.

You could try something along these lines:
http://www.terrypin.dial.pipex.com/Images/AMRFSignal.gif

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

 

[John Woodgate]

I read in sci.electronics.design that Melissa <melissa@colorado.xxx>
wrote (in <SvednbC79OgYtt7fRVn-qw@forethought.net&gt about 'Freeware or
low cost schematic software?', on Thu, 24 Mar 2005:

What I'd actually like to do, is set up a loop and tune it to 60 Hz

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

 

[Melissa]

John Woodgate <jmw@jmwa.demon.contraspam.yuk> wrote :

I read in sci.electronics.design that Melissa <melissa@colorado.xxx
wrote (in <9eSdndI5LIlnJdzfRVn-2A@forethought.net&gt about 'Freeware or
low cost schematic software?', on Wed, 23 Mar 2005:

So I'd need to model a radio signal source, which I'm not sure how to
do with this,

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

and a loop antenna, which I'm not sure how to do,

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.

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.

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.

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

 

[Roger Lascelles]

"Roger Lascelles" <invalidl@invalid.invalid> wrote in message
news:3a7kr0F680nlnU1@individual.net...

"Melissa" <melissa@colorado.xxx> wrote in message
news:AeednQIS154K9aPfRVn-qQ@forethought.net...
Hey, is there any decent freeware or low cost schematic software out
there
that's good?

I have thrown out Protel schematic at work and now use TinyCAD - a
freeware
schematic editor which I reckon is heaps superior. TinyCAD exports a
netlist which I suck into Protel to do the PCB.

TinyCAD is easy to learn, with Windows standard controls, so you don't
have
to remember how to drive it. The schematics look good when printed. It
can
do big jobs with many sheets, so it won't run out of grunt.

It loads and runs fast on Windows, so you can use it for a quick diagram.
You can copy and post bits of schematic from it, which is great for
documentation or email.

My only warning is : look at but don't use any of the supplied libraries.
They are donated bits and pieces, sometimes gotesquely mismatched, and
with
pins off grid may not actually connect when you expect. Start your own
library with pins nicely on grid and all will be well.

Roger

Forgot to give the TinyCAD link : http://tinycad.sourceforge.net

 

[Melissa]

"Robert" <Robert@yahoo.com> wrote :

"Melissa" <melissa@colorado.xxx> wrote in message
news:AeednQIS154K9aPfRVn-qQ@forethought.net...
Hey, is there any decent freeware or low cost schematic software out
there that's good?


Linear Technology offers a free Schematic Capture and Spice Engine
called Switcher CAD. There's a Yahoo group to help with any issues and
the bug fixes come very fast.
www.linear.com/company/software.jsp

I guess when you get something for "free", you get what you pay for. I
downloaded it because I wanted to try out this spice stuff, never have
before. I was thinking of looking at a crystal diode detector circuit and
seeing how it modeled it, but they don't have any germanium diodes in
there. Darn.

Yes, I actually have some germanium diodes, after all these years, in my
lab drawers somewhere, brand new.



--
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