Could I doing pcb mount ssr with G3VM-353G?

electronics
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#1

Summary: Continuing my search for a solution to my problem, I have landed on normally closed solid state relays (NC 1 FORM B SSR). Could you tell me if I’m doing this right?

What I need: What I need, is a switch, that is closed when the power to my MCU is off, and that is open when the power to my MCU is on. I have a 12V PWM coming in and when power is on, I substitute it with my own 12V PWM. (Basically a normally closed switch, which opens completely when power is on.)

In the schematic below, I have tried to illustrate my situation.

Why I need it: Since PNP Transistors (due to high Emitter-Base Voltage), P-MOSFETs (due to at times negative Source-Drain Voltage) and JFETs (due to maximally 12V available as control signal) don’t work, I have landed on SSRs.

Though I’ve learned alot about solid state relays here:http://www.apogeeweb.net/article/65.html, I have no experience with PCB mounted SSRs, so I need your help. I found this relay which seems to suit my application: G3VM-353G. Do you think this will work as intended?

Schematic 1: My “challenge”/problem

simulate this circuit – Schematic created using CircuitLab

Schematic 2: Will this work?

simulate this circuit

Thank you!

Edit specifiying the signal: As per request: The PWM signal to be passed through or interrupted is a 1kHZ, normally 0-12V, 0-100% duty cycle signal. To pass through states, the amplitude is sometimes modulated, changing it to 0-9V, 0-6V or 0-3V. Current is minimal (except for measuring, no current is drawn from the signal). Voltage drop tolerance is ±3%, duty cycle tolerance is ±0.1%.