ESP8266 Community Forum

Different SSR have different turn on voltage, please check the datasheet of your model.

One more thing about SSR is that, unlike mechanical ones, they exist "half- on" state, when the voltage is in their linear response region. And you need to carefully avoid getting to this state, because that's when they as like a resistor, and when large current pass through, they can get very hot, literally melt themselves.

Guess how I figure this out...

Has any body shown the input voltage range. I checked my vintage[1980+] the input range is 3v-32v
I would not attempt to use these @ 3.3 volt , but they probably would work...

I probably also use a transistor switch to help isolate the ESP.

I never heard of SSD half on unless it was defective,, but anything is possible..

xtal wrote:Has any body shown the input voltage range. I checked my vintage[1980+] the input range is 3v-32v
I would not attempt to use these @ 3.3 volt , but they probably would work...

I probably also use a transistor switch to help isolate the ESP.

I never heard of SSD half on unless it was defective,, but anything is possible..

Yes you probably want to signal the SSR at least at 5v.
For that you need an optocoupler.

Half-on is achieve when you signal the SSR very close to 3v, like 2.7~3.0v.
It will be conductive, but the voltage drop across it is high. Put a large current through it, P=IV, it will be unable to dissipate all that heat.

No need for opto-coupler if the SSR have higher input voltage. Simply use a N-MOSFET to cathode, and anode to +5V.
And if you have lots of SSRs, you can use multi-channels MOSFET chips such ULN2003 or ULN2803.