12v Solid-state relay circuit w/ 0.8v trigger

Thread Starter


Joined Feb 1, 2019
Hey guys,

(Photos below)
I just came across a small device that will will allow you to use car speaker inputs to allow you to trigger on or off a 12 volt Supply. The device is definitely solid state. It also has a 1 sec delay.

It has a very low trigger voltage of 0.8 volts

I thought about using one of those hobby grade blue relay modules but they need a much higher voltage in order to trigger the relay.

Anyone know what components / circuit this thing is using?

Any help would be appreciated. Preferably a circuit diagram:rolleyes:

pac tr-4.jpg


Joined Jan 23, 2018
Rather than guessing about the contents of a module, please let us know what the actual application is and certainly we can come up with a circuit that will work very well, be more reliable, fit in a smaller space, and probably cost less.


Joined Jan 21, 2019
The 1 sec delay is so that the speakers don’t “pop” as they turn on. Same reason you put your studio gear on delays with the speakers coming on last.


Joined Jan 23, 2018
OK, since we got no more details, I am guessing that it is a car stereo radio and the plan is to switch on the amplifier after the radio is switched on. Some car radios have an output to extend a powered antenna when the radio is switched on, and some radios even have an amplifier control output. One way to trigger the amplifier when the radio is switched on would be to have a current sensing relay in series with the power feed for the radio. But that will not have any delay at all. But the current sense part is easy, just a few turns of wire, perhaps #18, wrapped around a reed switch. Then that can trigger the delay to switch on the amplifier.