Electronics > Beginners
DC SSR Won't turn off
MatCat:
I am using a DD220D10 DC SSR being driven by MAX4820 at 5V for control, and the supply is 72V 1400ma constant current supply, and the load is 100W LED, when all is powered reguardless of control signal (even directly grounded) the SSR will stay on. Any ideas how to get it to work properly?
Zero999:
There are two possibilities:
1) LEDs can light with a very small current and solid state relays leak a considerable current, even when off.
2) The SSR has failed short circuit, which is the most common failure mode.
Test the solid state relay with an incandescent lamp. If it works, then it's #1 and the solution will be to connect a resistor across the LEDs. If it still doesn't work, then the solid state relay is bad and needs replacing.
wraper:
Part number suggests it came from ebay or aliexpress. I won't be surprised if it's not even DC SSR internally. FFS don't buy them from china, they ARE fake crap which is not safe and not nearly meeting specs. If you want it cheap, build your own from discrete components. In many cases SSR is not even needed, and simple MOSFET is more than enough.
kosine:
Yep, at that power level you've probably cooked it. They tend to fail close circuit. Would need a big heatsink and ideally a fan for what you're doing. Something like a CPU cooler should work.
I've bought quite a few of the cheap Chinese "fotek" SSRs over the years (both DC and AC), and not actually had any bad ones yet. (Tempting fate here, aren't I...)
A couple of them have been used in factory machines and are still going strong. Maybe I just got lucky, but I must have used about 20 from different suppliers by now.
MatCat:
I know the relay wasn't failed before, I used the same relay to switch 50 watts with no issue (36v 1400ma), but with 100 it's no go, I will test the relay and see if it got cooked. The LEDs seem to be coming on full tilt, not partially as if A really low current.
Navigation
[0] Message Index
[#] Next page
Go to full version