Relay vs christmas lights

Hello everyone,
I built a circuit that receives some appropriate signals from an Arduino UNO and command to 24 (3x8) SSD relays.
I used ssd relays and all it seems working fne, the leds on the relays lights when I want.
But when I plug a christmas lights led strip, the leds light up. Always: with a weak light when relay is powered off, with "nrmal" light when relay is powered on.
If I measure the voltage is 110V when relay is powered off and 220/230 V when powered on.
Even when I disconnect Arduino, with relay externally powered, leds light up with a weak light.
If i plug a light bulb all works fine. If I don't use SSD relays, but mechanical relays, all works fine.
Only with SSD relays I have this problem, it seems that the "diode bridge rectifier" (if any) of the led strip causes this issue with SSD relays.
Any ideas on how to avoid this behaviour?
Thanks a lot,

This is the circiut.

Who can tell with out schematic of your project. Remember, your SSR only will work with AC and bridge rectifier, well, rectify the AC to DC.

I wonder if running the hots and grounds together in a star pattern would help.

Thank you Paul,
I sent a pic of the project.
I can power off Arduino and the circuit you can see at the top center, leaving on only the relay power supply. Connecting the led strip to one of the clamps, le leds light on with weak light.
Strange, isn't it?
Thanka again.

A picture is not a schematic. You'd have to clearly explain how the power is connected to and from the source, supply, and ports. You may have unintentional connections.

What is written on the body of the SSR module ?

Nice job wiring.

I have two thoughts:

  1. Leakage from the SSR relay. I.e. some very small current that runs through the output device even when off. Perhaps from a crossover detection circuit. LEDs require so little power this leakage can make them light but be dim.
    Post the SSR relay partnumber / specification link.

  2. (much less likely) I can't see from the photo, is the bottom of the SSR board in contact with the wood? The wood may not be a good insulator.

Most / all AC SSR's are isolated from input to output. I would guess there is no ground loop on the input side that could cause this except something that caused a signal on the SSR input.

Hi @geppox

Can you make a schematic, (can be freehand), of the LED circuit?

RV mineirin

Check all your terminal strips for 'whiskers', small lengths of wire not fully in the cup on the strip.  This can cause shorts between adjacent wires.

SSR board

Where does the UNO's +5v supply come from?

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I'm going with leakage. It would probably work fine with a higher current load like a regular 60W light bulb). There would still be leakage but the voltage will drop and it wouldn't be enough to light-up the light bulb.

The same thing can happen with a light dimmer if the load is too "light" (a low-wattage load) and it won't dim all the way to "off".


Triacs leak, when off they are a high resistance, not an open circuit like relay contacts. You might try a low wattage incandescent bulb (2 or 3 Watts) in parallel with the LED string to pull the leakage voltage down.

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This is the schematic of the circuit.
In the three relay outputs I didn't use 10 pins, because vcc is not needed for ssr relays. Only pin 1-8 and gnd.
The relays are externally powered with a 5v power supply.
Arduino Uno is powered from a laptop.
I connected together the ground of the circuit and the ground of the power supply (I don't know if this is correct).
However, as I said, the led strip light on (weakly) even with Arduino (and therefore the circuit) powered off, when I give power to the relays I have in output 110 V.
Thanks a lot to you all.

What is written on the body of the SSR module ?

Each of the 74HC595s needs a 100nF ceramic decoupling capacitor close as possible to the 5v pin.

This is the relay module I used.
From amazon:ÅMÅŽÕÑ&crid=STXR4PZOPZCA&dchild=1&keywords=ssr+relay&qid=1635032190&qsid=257-8271376-5644261&sprefix=ssr+relays%2Caps%2C73&sr=8-14&sres=B071HP9NJD%2CB07HT2BCKN%2CB08FWWRK2Y%2CB0716RTYMD%2CB07J5NR3XK%2CB07QML88BF%2CB07MBGF4W8%2CB093GGMJXN%2CB0752M8MMG%2CB005T7F3HE%2CB071462VL4%2CB07DR9PX7P%2CB07RLST1NG%2CB07QJYMC4W%2CB07Q81M988%2CB07QMSB6Z5%2CB07QPZ67D4%2CB07QS44SYH%2CB07QPMRDQY%2CB07PRW26B1&srpt=RELAY

Don't know if this helps...
Thanks again

There should be a number written on the side of each SSR relay, what is it ?

Last posts says to add decoupling to the 74HC595 registers too.

The relay with numbers and other stuff :slight_smile: written.
And the box with the led rectifier for the strip.

You really need to test the theory in reply #11 and #12. I think it's correct.

The 202P on the relay confirms the relay is for 220v operation.

  • Yes, add a heavier load on a relay to see if the LED string operates properly.

  • Add decoupling on the 74HC595 registers.

  • Move the Arduino GND going to the left relay board to the 5V power supply GND terminal.