Forums » CircuitLab Feature Requests

Instrumentation amp ICs are in common use. It would be nice to see them as standard parts in your emulator. In particular, the INA114 and the INA129 are excellent experimenter parts.

I would also appreciate seeing models for a couple of optical devices, including the Avago HNRC200 - commonly used optoisolator for linear circuits, and the VTL5C4/2, which is popular among musicians.

Thanks. I one your project.

I agree. Optocouplers/Optoisolators would be a tremendous help to some of us.

An optocoupler is just a current-controlled current source, pretty much, close enough. That already exists. Maybe put a small capacitor across it to simulate slowness.

@Mark_Cohen, @fjbasile,

A lot depends on how accurately you want to model your circuit.

A slightly more advanced optocoupler model than @arduinohacker is talking about but still some way from representing a realistic device model:

Even manufacturer's SPICE models are often quite inaccurate. I have done some much higher accuracy models for some vendor's parts largely using behavioural rather than physical modelling.

I believe some of the Avago and a few of the more recent Vishay models are some of the more accurate ones.

It's easy enough to build an instrumentation amplifier from the primitives available in CL.

One big gotcha is the very loose tolerance on current transfer... Some have a typical range of 50 to 600%, which is more than a decade of possible current gain.

Yes, I solved MY problem by creating a current controlled current source, but it would have been much easier to drop in a complete part. Yes, I can wire up an instrumentation amp with 3 op amps and seven resistors (maybe a few caps and diodes to make it more accurate), but it would have been easier to just place a part. Come to think of it, they make those as chips, right? It's only a matter of convenience. The simulator can model anything, but is most useful if there is a database of common parts.

Anyway, this isn't intended as a complaint or bug report - just a request to add a few common components if the CircuitLab developers think that having them there improves the tool enough to take the effort. I am more confident that the instrumentation amps will be used than that the optos will.

Thanks to the developers for this amazing tool. It has found its way into my classroom at UCLA.

@Mark_Cohen I take your point.

CL could do with a bigger library of parts, a way to organise them and a way to handle subcircuits and hierarchy.

Some of the framework for subcircuits and hierarchy is already there in the custom symbol but as yet there doesn't seem to be a way to attach a schematic to a symbol.

When hierarchical design appears then it will be possible for users to create parts and re-use them, at least locally, possibly sharing globally them in the same way as top level circuits.

When subcircuits appear then users should be able to create parts and share them globally, possibly being able to add them to a library of user contributed parts.

That of course requires a more structured approach to libraries.

BTW, although this is yet more circuit building rather than a component, have you seen this thread on CdS photocell modelling (which is the basis of the PerkinElmer VTL5C4/2 Vactrol)?

https://www.circuitlab.com/forums/support/topic/j6zzht96/how-do-simulate-photoresistor-light_dark/

Thanks. I will look at the thread.