LT Spice help

Thread Starter

Sourena

Joined Jul 7, 2020
3
Dear guys,

I was wondering about a problem in my designed capacitive sensor, why the simulation is not executed as wished.
When I simulate the output difference between Vout1 and Vout2 without connection to the Schmitt trigger it looks like really well, but when I connect it to the Schmitt trigger, in order to make the difference digitlly readable, this signal looks to be pulled up and swings about 5 V higher. I would be thankful to you, if you could help me.
 

Attachments

ronsimpson

Joined Oct 7, 2019
726
Part of the problem is R7:
1) change R10 to 200k. or
2) change like shown below.
Either either will make a signal on U1 output.

1594156708384.png
 

Thread Starter

Sourena

Joined Jul 7, 2020
3
Part of the problem is R7:
1) change R10 to 200k. or
2) change like shown below.
Either either will make a signal on U1 output.

View attachment 211580
Thank you very much for your reply. I believe that I have to choose the first one, because in your picture another difference has been measured, which I do not want to have.
Can you please tell me a bit about that? When I do that the difference between Vout1 and Vout2 is not anymore completely sinosoidal. How can I fix that?


1594159666353.png
 

Papabravo

Joined Feb 24, 2006
13,961
Why do you think it is appropriate to show a fragment of a circuit and ask for help. The explanation may involve things we cannot see. Like, where is your ground reference?
Even better would be to include your .asc file so we can run the simulation for a better idea of what is going on.
My guess would be that you have introduced a strong non-linearity, as you have near vertical edges in both directions.
 

Thread Starter

Sourena

Joined Jul 7, 2020
3
Why do you think it is appropriate to show a fragment of a circuit and ask for help. The explanation may involve things we cannot see. Like, where is your ground reference?
Even better would be to include your .asc file so we can run the simulation for a better idea of what is going on.
My guess would be that you have introduced a strong non-linearity, as you have near vertical edges in both directions.
Thanks for your reply but I had already uploaded my asc. file as I asked my question
 

Papabravo

Joined Feb 24, 2006
13,961
Thanks for your reply but I had already uploaded my asc. file as I asked my question
Missed it.
I ran the simulation and got the following plots:
Gesamt.png
As you can see Out2 is a low level AC signal with an offset of 5V. I don't think this was your intention. Out1 looks normal. I don't think the opamp is configured properly. What is is that you want the opamp to do? The purpose of R4, R5, C4, and c5 escapes me. Can you provide some insight?
 
Last edited:

Papabravo

Joined Feb 24, 2006
13,961
I'm not sure exactly what you are trying to do so I just broke your schematic down, analyzed the pieces and redid it the way I would do it. It may not be optimal or correct, but I think it has a certain level of....ah....clarity. Yeah, clarity -- that's the ticket. Oh BTW --- Gesamtschaltung means the "Overall Circuit". Most amusing.
 

Attachments

sparky 1

Joined Nov 3, 2018
263
The simulation of a capacitive touch module involves the controller.
There are arduino simulators that emulate the functions of the arduino.
The module sensor circuit could be simulated but is less meaningful than the interaction with the controller.
 
Top