I have a normally closed solid state relay (link to datasheet below), that I would like to activate with 3V and deactivate with 2V. The load is a 24V 100mA LED. How should I go about this?

Datasheet for SSR: https://docs.rs-online.com/4030/0900766b81471bd5.pdf

Please let me know if I should provide more information.

  • \$\begingroup\$ You mean it should turn on when a certain voltage goes above 3V and then go off when it goes below 2V? \$\endgroup\$ Sep 14, 2020 at 10:32
  • \$\begingroup\$ No, it should turn on when the input voltage is 3V and turn off when the voltage is 2V. \$\endgroup\$ Sep 14, 2020 at 10:34
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    \$\begingroup\$ And what happens in between? Anyway sounds like you want to read up on comparators. If you want to actually hold state you may benefit from introducing a cheap MCU where you can apply some software filtering to the decision. \$\endgroup\$ Sep 14, 2020 at 10:36
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    \$\begingroup\$ Yes, what happens in between? \$\endgroup\$ Sep 14, 2020 at 10:53
  • \$\begingroup\$ Thank you, comparators sounds like a good idea. I have measured the voltage with a multimeter, and it just seems to change quickly. \$\endgroup\$ Sep 14, 2020 at 11:16

2 Answers 2


It is similar and I have a model for it. The result will be the same as yours. What you can use for driving is a CMOS Schmitt trigger (HC14, AC14 ...).



To achieve the solution 3 volt = On and 2 volt = Off you need two functions:

1, Schmitt-trigger (https://components101.com/articles/schmitt-trigger-introduction-working-applications) and

2. Flip Flop (https://en.wikipedia.org/wiki/Flip-flop_(electronics)) that will keep the state on the "solid state relay".

The Schmitt-trigger and Flip Flop can be realized with discrete components, logic ICs (https://en.wikipedia.org/wiki/List_of_7400-series_integrated_circuits) or a MCU (Micro Controller Unit).


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