I'm using my Raspberry Pi to control a solid state relay. I can pulse an LED output when the power is low, but when I increase the power a little bit, the output remains on, instead of pulsing on and off as expected.

Hi is my relay broken or am i doing something wrong?

closed as unclear what you're asking by Milliways, joan, goldilocks Jan 11 '17 at 17:00

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  • A couple of comments. 1) relay is the correct spelling. 2) Exactly what brand and model number is that relay unit? I can't tell from the video. My first stop is the tech sheet for that unit. 3) You probably want to clarify your question in text here, rather than relying solely on the video. – zipzit Dec 23 '16 at 5:03
  • Can you describe the problem? – Mark Dec 23 '16 at 8:02
  • 1
    @TomvanKeulen The first rule of stackexchange is be nice. Further rudeness will result in your suspension. – Steve Robillard Dec 23 '16 at 8:53

No, you really cannot use an AC (alternating current) solid state relay (SSR) to control a DC (direct current) load.

ref: http://www.omron.com.au/service_support/FAQ/FAQ02101/index.asp

The design of a Solid-state Relay will not allow it to reset if a DC load is used.

Explanation Solid-state Relays for AC load switching use thyristors and triacs as output elements. By turning Solid-state Relays input ON, the output can be turned ON, but simply turning the input OFF doesn't mean that the output will be turned OFF. This is because Solid-state Relays have a characteristic that it stays turned ON until the load current becomes zero regardless of the absence of input signals into Solid-state Relays. The DC current will never become zero, therefore it will not be reset.

solid state relay characteristics

The only real surprise here is that it blinks the output LED at all at low power. I'm guessing there is an internal threshold in place. If you are driving DC loads, you will want a solid state relay designed for that purpose.

For DC control of DC loads there are many options available, depending on your output voltage and current requirements, that may be less expensive. (Here's a rough list sorted by loads, small to big: optoisolators, basic driver circuit with BJT transistor, Darlington circuit, Mosfets, IGBTs or if you need it, DC/DC solid state relays) Reference

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