stupid ssr question

I finally started to put my control box together today (almost done!). And I decided to check every thing out. Every thing is good, but my ssr (when checking with my multimeter) is always on. Even when nothing is hooked up on the inputs. I pulled the ssr and put another one in, and the same thing. The only conclusion that I have is that it has to have a load to switch right... is this correct?

Yeah, SSRs are hard if not impossible to test with a standard multimeter, they leak enough current to appear to always be on. To test my control SW and SSRs I built a super simple test fixture:



Bulb holder was $1.30 at Lowes, everything else was scrap.

Took an appliance cord and stripped it down to the three conductors (lamp wire would also work). Wire the hot to the SSR and then from the SSR to the bulb hot. Then wired the neutral directly to the bulb. Plug the cord into a standard outlet. When applying the right control voltage (5-30VDC for mine) the bulb should turn on.

This gave me the ability to test duty cycle and frequency without using a heating element.

Also, many of the AC SSRs switch at the zero voltage crossing of the AC sine wave. So generally an AC supply/load needs to be supplied or they won't switch.

Thanks... Now I can sleep tonight instead thinking what the heck I did wrong. I should have everything for a live test tomorrow and then I can hook this up to my element.

TheFlyingBeer said:

Also, many of the AC SSRs switch at the zero voltage crossing of the AC sine wave. So generally an AC supply/load needs to be supplied or they won't switch.

Click to expand...

I had 240V hooked on to this. And my volt meter kept reading 240V on the load side of my ssr. I changed out the ssr and the same thing. So I was sure the ssr was good and the wiring couldn't of be any simpler, I figured it had to have a load to switch right, I couldn't think of anything else it could of been.

Yeah, you are most likely fine. Wish I would have known what I do like 6 years ago when I spent a long night in the lab troubleshooting an SSR with this exact same behavior. Wasn't as well versed in the Googles as I am now

Good luck tomorrow.

Same thing got me at first too. I had a couple old SSRs given to me and at first I thought they were bad. I almost threw them out but I figured I would test it with a load and sure enough they worked fine!

My my first batch of beer with this today and everything worked flawlessly!