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Simulating with LTSpice ?

I am trying to simulate a buzzer circuit with LT Spice. The circuit is supposed to be astable, but the simulator doesn't get oscillating. I think I need an initial condition, how do I add one ? I include the circuit, perhaps someone can go over it and see if it should oscillate. The 8 ohms R is the speaker. This is the .asc file:

Version 4 SHEET 1 880 680 WIRE 448 288 448 208 WIRE 448 368 448 384 WIRE 112 368 256 368 WIRE 112 112 112 208 WIRE 384 208 448 208 WIRE 448 208 448 192 WIRE 256 32 112 32 WIRE 448 96 448 32 WIRE 448 32 256 32 WIRE 256 112 256 144 WIRE 384 144 256 144 WIRE 256 144 256 224 WIRE 256 320 256 368 WIRE 256 368 448 368 WIRE 192 272 112 272 WIRE 112 272 112 288 WIRE 320 208 112 208 WIRE 112 208 112 272 WIRE -16 32 112 32 WIRE -16 368 112 368 WIRE -16 160 -16 32 WIRE -16 240 -16 368 FLAG 448 384 0 SYMBOL res 96 16 R0 SYMATTR InstName R1 SYMATTR Value 95k SYMBOL res 96 272 R0 SYMATTR InstName R2 SYMATTR Value 56k SYMBOL res 240 16 R0 SYMATTR InstName R3 SYMATTR Value 470 SYMBOL res 432 272 R0 SYMATTR InstName R4 SYMATTR Value 8 SYMBOL cap 384 192 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 32 32 VTop 0 SYMATTR InstName C1 SYMATTR Value 0.02µ SYMBOL npn 192 224 R0 SYMATTR InstName Q1 SYMBOL pnp 384 192 M180 SYMATTR InstName Q2 SYMBOL Misc\battery -16 144 R0 WINDOW 123 0 0 Left 0 WINDOW 39 24 132 Left 0 SYMATTR InstName V2 SYMATTR Value 9 SYMATTR SpiceLine Rser=10 TEXT -34 506 Left 0 !.tran 1

Reply to
Andy
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I think the reason is because you didn't choose specific transistor models. I specified non-generic models and it ran OK with no initial conditions in both CircuitMaker and in LT Spice:

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In fact LT Spice did the better job, as CM seemed to need a while to get going.

--
Terry Pinnell
Hobbyist, West Sussex, UK
Reply to
Terry Pinnell

I think it's a function of step size. Using 200ns step size and max step, it starts immediately.

BTW, How do you get the output to print out in 4 places?

--
Regards,
   Robert Monsen

"Your Highness, I have no need of this hypothesis."
     - Pierre Laplace (1749-1827), to Napoleon,
        on why his works on celestial mechanics make no mention of God.
Reply to
Robert Monsen

Thank you, it is working with your transistors :-)

Andy

Reply to
Andy
< snip>

It didn't for me, when I changed the transistors as terry suggested it worked, but not for the generic ones. If you did manage it, kindly post the .asc file

In LTSpice you just click on any node you want to monitor. Also, when the simulation begins you get to choose the nodes.

Reply to
Andy

Is that one for me, Robert? If so, can you clarify please.

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Terry Pinnell
Hobbyist, West Sussex, UK
Reply to
Terry Pinnell

Out of curiosity I just tried again with generics.

First I replaced the 2N3906 with a generic 'pnp'. (BTW, am I right that you have to delete the original to accomplish this? The generic is not listed in 'Pick New Transistor'.) That combination worked OK, with no changes of the default Step/Max times.

Then I replaced the 2N2222 with a generic npn. That failed of course, as it was now the original failing circuit. Implementing Robert's suggestion was a challenge for me, as although an experienced CM user, I'm new to LT Spice. I changed the Stop Time from 10 ms to 20 ms and the Step Time to 200 ns. (BTW, while doing this, in the Edit Simulation Command dialog, I noticed that there appear to be no default values entered for Time to Start Saving Data, and Maximum Timestep, just blanks. What values are being used?). On running that, even after several minutes I still had only two pulses. I halted it when the 4th pulse came up, around 13 ms. So yes, it *does* run with both generics - but glacially slowly.

Finally I tried the remaining combination, i.e. npn = generic, pnp =

2N3906. That ran OK, with your initial settings of Tran = 10 ms and Max = blank = ??

So, one generic is OK, but LTS doesn't like two! Hopefully someone like Mike Engelhardt or Helmut Sennewald will spot this thread and explain.

That query still puzzles me. Who was trying to 'get the output to print out in 4 places'? And how would your answer cover that?

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Terry Pinnell
Hobbyist, West Sussex, UK
Reply to
Terry Pinnell

With the LTspice prog' I never put a step time in. I'll just use something like, ".tran 1". Let the prog' sort it own steps out. regards john

Reply to
john jardine

Your waveform diagrams have 4 significant digits. I can't get CM to do more than 3.

--
Regards,
   Robert Monsen

"Your Highness, I have no need of this hypothesis."
     - Pierre Laplace (1749-1827), to Napoleon,
        on why his works on celestial mechanics make no mention of God.
Reply to
Robert Monsen

Ah - DECIMAL places! (I was thinking 'locations'.) You mean numbers like '4.000 V', '15.00ms' shown in

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? Can only see 2 there. Maybe you mean examples in other threads, like
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where I do see 4 sig digits on the X-axis.

That's just the way it displays in CM 2000 here when you zoom in on a section. Are you saying that for you it never goes beyond 3?

Anyway, given the variation/inconsistency due to other factors, 4 represents spurious accuracy IMO!

--
Terry Pinnell
Hobbyist, West Sussex, UK
Reply to
Terry Pinnell

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