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I want to evaluate whether I can switch an amplified audio signal (AC, load 8 Ohms, e.g. 20W) using a solid state relay. I already do this with mechanical relays. So I need an SSR with very linear behaviour, suitable for AC in the frequency range of 20 - 20K Hz, with very little ON resistance (ideally 0.1 Ohms or less), and very low leakage current when the relay is OFF. And I want to control the relay with a micro-controller, i.e. with a 3.3V or 5V signal. Disclaimer: I know very little about how a MOSFET works.

I was thinking about Omron G3VM-61AR1. What I don't understand is what kind of circuit I have to build "around" this component. It specifies LED currents and such things, but I need to ensure that I can apply a control voltage from the GPIO instead. Those components have four pins, which I also don't understand. "ready-made boards" usually come with stuff around the relay that gives you GND, Vcc, Control-Pin, and Load-In/Out, so five pins. Any help for noobie level would be appreciated. I guess my application is not unlike this.

My current understanding is, looking at the more detailed spec, that the LED "forward voltage" should be between 1.33V and 1.48V, so I could probably create a voltage divider, and just make sure I don't run more than the 15mA or so that the GPIO can handle. So instead of separate Vcc and Control-Pin, I just have a single control voltage input? Do I need to be careful about "reverse currents" or such things?

Edit: This related question would imply that I can just connect the GPIO if I use some 300 Ohm or so resistor.

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  • Those components have four pins, which I also don't understand ... pins 1 and 2 are two ends of an LED ... pins 3 and 4 are the relay "contacts" when the LED is lit, then the two mosfets conduct ... using your words, they areGND, Control-Pin, and Load-In/Out, – jsotola Jul 28 '23 at 02:29
  • @jsotola ok, so I guess the "modules" only carry explicit Vcc because of, say, an informational LED that is also driven? – 0__ Jul 28 '23 at 10:45
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    because of any component that requires it – jsotola Jul 28 '23 at 17:47

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I got a couple of G3VM now, and tested with a G3VM-61GR2 (rated 60 V / 1.7 A with a ON resistance of 0.08 R). I connect pins 1 and 2 via 330 R to the GPIO, and pins 3 and 4 to the 8 R speaker. It works very well, OFF attenuation and ON sound quality seem good enough for my purpose.

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