Suggestions for circuit simulator for understanding Op Amps

Thread Starter

PushToClose

Joined Aug 5, 2021
11
Hello,

I've had a look at a couple of free online circuit simulators, but struggled a bit to do anything useful with them. I'm trying to find a way of simulating a circuit using op amps, to see if I can achieve what I want using them. I generally find that I don't know where to start because there are 4000 op amps to choose from, or that there isn't a way to get all the inputs and outputs, or components, that I need to play around with. Does anyone have any suggestions of an (ideally free) circuit simulator? (I know it's a bit cheeky to expect good functionality and free to use, but I don't anticipate needing such a thing for any other use)

What I'm trying to do is get a Hall pedal input with a 0.8 - 4.2V range, to give me (via the circuit I create) a 2.5 - 3.9V range output. I then need to be able to activate a reverse switch (either physical or digital) which then changes the output range to 2.5 - 1.1V with the same pedal deflection (i.e. foot flat on the pedal gives 1.1V, releasing the pedal gives 2.5V). I also need the 2.5V output to be maintained while switching from forward to reverse (it will feed into an existing motor controller, which will detect an error and turn off if the signal is lost).

Another poster suggested a set up that will achieve the 2.5 - 3.9V range, and I'd like to develop that to incorporate the other stuff/see if the idea is actually possible.
 

crutschow

Joined Mar 14, 2008
27,967
Several here (including myself) use the free LTspice simulator from Analog Devices (as eric suggested).
It has a somewhat steep learning curve, but there are good tutorials available along with many Example circuit simulations in the included files, as well as help from us here, to get you started.

Below is an example op amp simulation from the Example directory included with LTspice.

1632748738425.png
 
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Thread Starter

PushToClose

Joined Aug 5, 2021
11
Thank you for this suggestion. I've downloaded LTspice (for Mac), but while trying to get started following some tutorials, I opened Draft>Components... and there is nothing to select; it's empty. Has anyone else had this issue?

Thanks.
 

BobTPH

Joined Jun 5, 2013
3,835
I have been using LTSPICE for 10 years, and have never seen menu items "draft->component". ???

To place a component, you first have to create a new schematic from the file menu. Then use the buttons that look like this:

1633952103903.png

to add a resistor, capacitor, inductor, or diode. Use the OR gate symbol for all other components.

Bob
 

Thread Starter

PushToClose

Joined Aug 5, 2021
11
Thanks for the reply - are you using a Mac as well? If I right click after opening a new schematic, "Draft" is the 5th option down in the menu, and "Component" is an option in the sub menu. The window doesn't have a toolbar at the top as in your screen shot (or rather, it does but with only three buttons on, which are not component buttons. I've tried looking for ways to display a toolbar such as the one you have, but haven't found a way).
 

BobTPH

Joined Jun 5, 2013
3,835
No, I am using windows.

Draft sounds like a command to draw a new component type, not place an existing one.

Bob
 

BobTPH

Joined Jun 5, 2013
3,835
OK, I was just following a YT guide. Maybe I should look at a few guides...

Thanks.
Okay, I took a quick look at a Mac tutorial. You have the correct command to insert a component. But the tutorial says it should give you a submenu at that point.

Bob
 

Thread Starter

PushToClose

Joined Aug 5, 2021
11
I was kind of hoping using a simulator would enable me to find out what kind of op amp I would need. Any suggestions for what to use to experiment on a breadboard with?

Thanks
 
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