I want to add snubber or supression protection diodes for a solid state relay. Here is the diagram without the diodes:

enter image description here

And this is the SSR I'm going to use: http://uk.rs-online.com/web/p/solid-state-relays/0346895/

What kind of diodes I need and where to place them? The load is a speed controller together with a single phase inductive fan-motor and will not draw more than 1A in steady state.

  • \$\begingroup\$ The datasheet shows a built-in snubber as an option; why do you think you need more? If you get one without a snubber, the equivalent schematic shows clearly where it is placed (values may be interesting to find, though). \$\endgroup\$ May 1, 2016 at 16:04
  • \$\begingroup\$ Sorry I don't understand if I order this relay, how can I know if it has built in snubber? \$\endgroup\$
    – user16307
    May 1, 2016 at 16:08
  • \$\begingroup\$ Btw someone shows connections for the AC output of the same realy totally different here: hobbyprojects.com/quick_circuits_reference/… Isnt that wrong? \$\endgroup\$
    – user16307
    May 1, 2016 at 16:16

1 Answer 1


RS state that that unit has an internal snubber but don't give the full Crydom part number so you can check.

enter image description here

Figure 1. Extract from Crydom Series 1 datasheet.

Contact RS and ask them for the full part number.

  • \$\begingroup\$ Thanks the snubber they show is R C in series not a diode. Why is that? \$\endgroup\$
    – user16307
    May 1, 2016 at 16:46
  • 1
    \$\begingroup\$ Wikipedia has a good paragraph on RC snubbers. It should give you a good appreciation. \$\endgroup\$
    – Transistor
    May 1, 2016 at 16:49
  • \$\begingroup\$ Using diode snubbers with AC power gets... complicated, RC snubbers don't have that problem \$\endgroup\$
    – Sam
    May 2, 2016 at 0:17

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