You probably also want a tightly regulated voltage supply or voltage reference powering this since that will directly influence the accuracy of the analog output. If you can transmit in digital and receive in analog then I recommend placing a low-pass RC filter and buffer at the VFD to serve as a simple PWM DAC and transmitting a PWM signal to it through an opto. This won't provide isolation for safety though since there is no isolation. "current-to-voltage converter" at the VFD (which is just a resistor of the appropriate value). You can transmit current-to-current or current-to-voltage by using a If you need isolation for signal integrity, and not safety reasons, and need to both transmit and receive in analog but it does not need to be voltage, consider using current signals. But you don't have much choice if you must transmit and receive in analog voltage. You really don't want to be dealing with linear opto circuits as a newbie (I haven't really been able to understand them either). There are linear optos and what sets them apart is they have two matched photodiodes so you can use the other for feedback to achieve linearization. Even pre-packaged analog isolators are kind of ungainly not to mention rare and expensive. If you're looking for one of those you won't find one. Isolating analog signals is a pain so know that there aren't really simple neat and tidy solutions. (In my case specifically, there are 2 types of optocouplers available at my uni so would like to know how to select one rather than a specific recommendation).Īlso, I know there may be other, simpler ways to achieve my purpose of signal isolation for my VFD control, but I am interested regardless in the answer to this question using optocouplers I was hoping for a detailed explanation for someone who is a novice in circuitry that could explain how to set up this circuit ideally with non specialized optocouplers, or if specialized optocouplers are required, how to evaluate a specific optocoupler for its appropriateness. I understand that optocouplers can be used to transmit digital signals as well as current across the optocoupler which may in some applications be leveraged to isolate an analog voltage signal if you set up the circuit correctly to convert and pass current rather than voltage. One is a 0-5V analog voltage signal that give the VFD its set point. I am trying to isolate control signals that are used to remotely operate a variable frequency drive.
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