I purchase a Sainsmart 8 Channel Solid State Relay board to control an 8 zone sprinkler system via an Arduino Duemilanove w/ ATmeg168. The SSR's LED lights up but my solenoids do not activate at all.

I admit I have no idea what I am doing. But here's how I connected everything:

I connected the Arduino digital outputs 2 - 9 to SSR inputs 1-8. Also, I connected a 26.6 VAC 650 mA power supply (from my Rainbird controller) to the SSR's VOC and GND connections. Specifically, I connected the wire with the white strip from the power supply to the VOC on the SSR board. The other wire from the power supply was connected to the GND. Each solenoid (two wires) was connected to the SSR outputs - common solenoid wire to the silver SSR connector and the other solenoid wire to the copper SSR connector.

I wrote a simple program on the Arduino to cycle through each Arduino digital output for one minute with a 10 second pause between each relay/sprinkler valve. The blue LED lights up for one minute goes off for 10 seconds and then cycles to the next relay. However, my solenoids are not activated at all.

What is wrong?

  • \$\begingroup\$ Don't they have tech support or a forum or anything? \$\endgroup\$
    – vicatcu
    Commented Aug 12, 2012 at 4:23
  • \$\begingroup\$ @vicatcu - they do have a forum but it seems pretty deserted (or new). None of their modules come with documentation either. They also have a wiki on each item but it's quite well hidden and not much help for a beginner from what I can see. Maybe that's why we get so many questions about them here... \$\endgroup\$
    – Oli Glaser
    Commented Aug 12, 2012 at 4:54
  • \$\begingroup\$ @Oli - Many questions about Sainsmart were from the same user, who seemed to jump from one module to the next. Didn't get it working, didn't learn from answers, and hop, next module. And the same questions returned. \$\endgroup\$
    – stevenvh
    Commented Aug 12, 2012 at 9:19
  • \$\begingroup\$ Issue Resolved. As previous poster indicated: I did not power the relays correctly. Thank \$\endgroup\$
    – user11468
    Commented Aug 12, 2012 at 21:34
  • \$\begingroup\$ bill, if the answer that Oli Glaser provided was correct (solved your issue) please accept his answer. \$\endgroup\$
    – W5VO
    Commented Aug 12, 2012 at 21:38

1 Answer 1


You didn't link to the relay module in question (I see you're new so no worries, please try to do it next time ;-)) but I'm assuming it's this one.

If this is the case, then I think you have mistakenly connected the 26.6 VAC supply to what is meant for a 5 VDC supply. If you have this is not good, hopefully it hasn't blown anything (very possible though)

The marking are actually VCC (not VOC) and GND. TO these you need to connect a 5VDC supply as mentioned.

Here is a schematic of one of the relays on your module:


Notice the 5V on the input side of the relay. The "switch" is from pins 3 and 4 with a fuse in series.

For the relay connections, they act like a single pole single throw switch (SPST) and need to be in series with the power source. To switch the power to the solenoids, you need one lead from the power supply (either one as it's AC) to one of the relay terminals, then one of the solenoid leads to the other terminal. Finally the other lead from the solenoid connects to the other supply lead.
Just try to think of the relay as a simple switch.

  • \$\begingroup\$ Thanks for your reply. Your assumption regarding the SSR link is the correct one I am using. So, I think I understand what your saying except for one question: where is the power to activate the solenoids? \$\endgroup\$
    – Bill
    Commented Aug 12, 2012 at 5:09
  • \$\begingroup\$ OH, OK i think I got it. I did not read the solution carefully. Thanks, let me try this. \$\endgroup\$
    – Bill
    Commented Aug 12, 2012 at 5:11

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