Solid state relay trouble?? [SOLVED]


I'm trying to troubleshoot my project and I'm stuck..

This post follows a thread I opened ( and my many tries to get everything working brought me to seek for electronic help!

I thought it was a sw problem but I was wondering...

Can a solid sate relay piloted by arduino turning on and off a 12v switching power supply cause my software to crash???


spycatcher2k: How are you driving the relay? Do you have a datasheet or link to it?

Shure! I should have thought of that... The arduino is an uno r3

the ssr is a s202s02f (sharp) It is connected to: arduino ground >>> - pin 7 >>> + hot wire from mains in and out as a light switch...

The power supply getting turned on or off looks like the laptop ones.. is 12v dc out and can supply 84Watt.. (about 7A)

Nothing more...


spycatcher2k: have you got a resistor inline with the output pin?

No, nothing. just arduino pin and straight to the ssr +


It is connected to: arduino ground >>> - pin 7 >>> +

You need a current-limited resistor between the Arduino output and the SSR. (180 Ohms will give you about 20mA.)

Usually SSRs have the resistor built-in, but this one apparently doesn't. Without the resistor, Yes, it's possible to "crash" or even damage the Arduino, or damage the SSR.

Right! Tried a 180 ohms and it did changed something... As now things runs a little longer than before. It is an improvement.

I will try an higher value resistor as suggested by spycatcher2k. Will update!

Hurray for the improvement anyway! :)

While I keep testing, let me just ask also this before I try to fry something else...

I'm also, with the same arduino controlling via pwm a 7 meters rgb led strip. It pulls roughly 2.3Amps per channel Last night one of the three tip120 used for the scope, connected to arduino with a 220 ohm resistor in between, got very hot to the touch then fried (well, was still turning off, but at very low pwm values the strip was just too bright to be right).

Shuold I replace it or just forget about them and get some power mosfets?

Note that in the box I'm using there will be few holes for passive ventilation (as it also contains the 12v power supply) but I really got no space for a proper dissipator (how to calculate how big it should be?)

spycatcher2k: Then you MAY be pulling to much current - try a 220 - 470 Ohm resistor inline.

330 Ohm resistor inline for both ssr... Still crashing. It now runs for a little while though. It was running for a much shorter period before...

I've also tried to replace the atmega on my arduino with another I had. just to exclude it was that causing the problem. It was not. Strange behavior appear from adafruit color sensor.When arduino crash, It's led appear like is dim (it should be off) or at times light up when it shouldn't be...