I have a solid state relay that has 5 to 24Vdc input requirements, and 24 to 240Vac~10amps load limitations. Can I hook up a DC load to the load side of this? I don't understand why I could not, and how to determine the limitations of the DC load given the AC specs. The relay is an OMRON "G3NA-210B" and the documentation mentions "photoisolator=yes".
Solid state relays are typically thyristor ot Triac based internally.
While you would be able to use a DC supply with one the problem is that the relay will not turn off until the voltage applied across it reaches 0 volts. This zero crossing detection is also used by the internal control signals to re-fire the triac each time the AC voltage starts up again (120 times a second for 60 cycle power) as long as the control signal is present.
This is typical of all general purpose solid state relays.
Thanks Dave22, I understand now. I may run across an application someday where this info will be useful in a DC circuit. Any thoughts on what the DC amperage limitations would be?
The current limitation should be the same for both AC or DC. Since the device you mention is fro a 10 amp load that is the maximum current I would expect it to be able to handle. Be aware though solid state relays generally need to be mounted on a heat sink since they typically drop a volt or two even when turned on. That would mean at
10 amps that you would need to be able to dissipate 20 watts. Most of the cases will not be able to handle more than 1 watt continuously without a heat sink.
Assuming I know exactly what you're looking for with the way you asked it.
You can connect a DC load on one side of the SSR how ever, since the SSR operates on AC, you would need to rectify it first before it goes to the DC load.
If your idea is to control a DC source to this DC load, then you have a problem. These devices will latch on. The only way to turn them off is to remove the DC source from the input side of the SSR, disconnect the load or lower the load or source enough below the holding current.
You could use a unfiltered AC to DC bridge source for example where the valleys will drop low enough for the SSR to unlatch.
On the load side of the SSR, I guess one could simply filter it if one wish to :).
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