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Circuit Simulation

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ScuzZ

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I use Livewire to simulate circuits.

I've attempted to apply this circuit numerous times but can't get the LED's to blink.

Any suggestions?
 

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It could happen for real. The simulation program thinks the transistors, resistors and capacitors are exactly the same. Both transistors turn on at the same time. Then the circuit latches instead of oscillating.

You need to do something to make one transistor turn off for a moment to kick-start the oscillation.
 
So if I put a push to break switch on the base of one transistor and broke the 'latch' it should start to oscillate?

This could also happen on a breadboard too couldn't it?
 
This simple circuit is called a multivibrator. Some articles on the web say it is possible that it will fail to start oscillating.

Try adding a pushbutton to short a base to ground to start it.
 
This is what I've done. Even when one transistor base is shorted to ground, the lights don't begin to blink. They just stay on.
 

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Q2 in your second schematic is connected incorrectly.
Livewire should have an Initial Condition operator (component, etc.). In Spice, the command is
Code:
.ic v(b1)=0
which forces the voltage on the node named b1 to zero while the initial operating point is computed.
If you can set the initial condition of one of the bases to zero, the multivibrator will start.
You could also apply a short current pulse to almost any node to upset the equilibrium.
 
I can't find anywhere, that allows you to put in an 'Initial Condition'

If anyone that uses livewire can point me in the right direction, the help file seems a little lite.
 
Did you pay money for that? I downloaded the demo. Mmmmm...
Linear Technology's SwitcherCAD III is totally free, and it is actually a serious Spice-based simulator. It does not have the toys (virtual instruments) that LiveWire has, but I believe it has a lot more capabilities in other areas. It is probably harder to learn to use if you don't have previous Spice experience, but there are several users here who know it pretty well, so you can get help if you need it.
 
Make the gains of the transistors, the values of the resistors and capacitors all slightly different, then it'll probably work.

Your simulation software looks pretty play school, it looks like an old version of Chrocadile Clips to me. I use the aforementioned but only for circuit diagrams; I don't normally rely on simulation software at all.
 
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