Struggles with simulation in LTSpice

[Ravi]

Hello!

I'm relatively new to LTSpice, I have a project to simulate in LTSpice. I appreciate any help you guys can afford. the project is a distance measure using ultrasound transducers. I have a timing generator which generates a square wave to start TX to send an ultrasound signal and a sawtooth signal wich feeds Sample and Hold circuit. When RX recieves an echo signal, it sends it to an amplifier wich enables Hold state. The voltage that is held is sent to VCO (using 555 timer) wich generates a proper signal according to Hold voltage, see attached block diagram and LTSpice file.

My headache is the transmitter TX which it generates a 40 kHz signal when it simulated only with the timing generator but when it is simulated with the whole circuit, it generates a 20 kHz! And i don't have a clue of why!

thanks in advance!

[HackedFridgeMagnet]

you have a couple of sub circuits that you should upload too.

.LIB C:\Users\Rawi\Documents...\Prosjekt\LTspice-extra-\lmc6482a.sub

.lib C:\Users\Rawi\Documents...\Prosjekt\LTspice-extra-\lm324.sub

[Ravi]

Hi HackedFridgeMagnet!

Thanks for the fast response!

I tried to upload them but it was not possible with .sub files so i changed to .txt. I hope it is okay?

[Zero999]

Hi HackedFridgeMagnet!

Thanks for the fast response!

I tried to upload them but it was not possible with .sub files so i changed to .txt. I hope it is okay?

No, don't do that. Paste them into the .asc file, as SPICE directives, that way it's all one file. I don't have time to try to get it to work at the moment, but here's your .asc file, with all of your models embedded. I tried skipping the initial operating solutiion and starting with power supplies at 0V, but it didn't work.

[Ravi]

Thanks Zero999!
Appreciate that !

[Zero999]

I've had a look at the simulation. The problem is it was generating convergence errors. I got it to simulate by changing the op-amps to generic models with the slew rate, bandwidth and input impedance set to match the data sheets.

I don't think the circuit does what you want it to though.

You should break it down into sections and simulate each individually, rather than plugging the whole thing into the SPICE.

[Ravi]

Hi Zero999!

I really appreciate what you have done!
As you mentioned, i should break it down to smaller circuits.

Have a nice day/evening!