Simulating with LTSpice ?

[Andy]

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 0.02ľ
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

 

[Robert Monsen]

Terry Pinnell wrote:

billycute@tiscali.co.uk (Andy) wrote:


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:


snip

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:
http://www.terrypin.dial.pipex.com/Images/BuzzerCM.gif
http://www.terrypin.dial.pipex.com/Images/BuzzerLT.gif

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

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.

 

[Terry Pinnell]

billycute@tiscali.co.uk (Andy) wrote:

snip

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

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

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.

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

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

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?

--
Terry Pinnell
Hobbyist, West Sussex, UK

 

[john jardine]

"Terry Pinnell" <terrypinDELETE@THESEdial.pipex.com> wrote in message
news:fkooq05qoltdvd77mrs9m7c4loddpetlss@4ax.com...

billycute@tiscali.co.uk (Andy) wrote:

snip

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

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

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.

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

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

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?

--
Terry Pinnell
Hobbyist, West Sussex, UK

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

 

[Robert Monsen]

Terry Pinnell wrote:

Robert Monsen <rcsurname@comcast.net> wrote:



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


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

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.