I have a Crydom D1D07 solid state relay and the control side is a +5 V DC on terminal 3 and a +3.4 V DC (don't ask) on terminal 4.
When terminal 4 is switched to ground (from +3.4 V DC) the SSR closes and the output side closes and passes the voltage as expected.
However, when the control side goes back to +3.4 V DC from ground the SSR does not open but remains closed and so the output side continues to pass voltage.
- The minimum on voltage is 3.5 V DC
- Minimum input current is 10 mA for on state
- Must turn off voltage is 1 V DC
- Impedance is current regulated
It seems the must turn off voltage is not being met.
Adding a 370 Ω resistor to the terminal 4 side corrects this failure above but I still do not see how it does. The math does not compute. I think the voltage goes from 3.4 V DC to 3.7 V DC with the resistor added.