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Topic: arduino to control a relay to turn on/off 120 volt lights. (Read 4566 times) previous topic - next topic


This is not an LED project, per se.  Please do not kick me out; since I have learned a lot in reading these forums and practicing projects.  I just was not sure which forum to place this question into. 

I purchased an arduino (uno version 3).  I have worked through the basic tutorials (on this site and something called Ada Fruit) and I am having fun; I did some electronics in H.S. and built my ham radio and although it was 40 years ago, I have magically r
remembered some of my fundamentals.

While looking through LED projects, I found a LED light display called "Knight Rider"  I got it to work and thought it would make for a great light show.  My question is this. 

I realize the output pins are either high or on and low or off. Maybe I am wrong on this, someone could correct me.   Could it be possible to route the wires from the Arduino to a solid state circuit and have it power regular LED 120 volt (10 amp) string of lights?  I saw (therefore 'stole' the idea) from a blog called Chivery Timbers where he used a Raspberry PI to control lights and sound.  I don't want to do something that elaborate, but he was using small transistorized relays to control the 120 volt lights.

I also saw something by a company called sain smart and they make a 5 volt relay which, I think does the same thing (opens and closes a circuit based upon a signal, in my case a wire from the output pins in the arduino and completes the circuit on the 120 volt side.    Am I on the right track?  Does what I ask make sense?

Does anyone have any experience in this? I have looked through these forums, and found nothing as to what I am trying to do.  Someone may have tried this, as I have never had an original thought, I 'steal' code and ideas (and would never claim to be original)  someone else has written, but have a small knowledge of BASIC where I can 'tweak' things.


Check out solid state relays at Jameco.com(or your favorite parts supplier).  The input is often 3 to 30 volts dc  and around 10mA (Arduino compatable) and there are versions that control 110 -240 volts ac at various currents (1 to 40A). 
You will save everyone's time if you read and follow the forum guidelines.  :)          


One can certainly control 120vac circuits using an arduino by using either electromechanical relays or SSR relays. The SSR have an advantage in they can be directly driven by an arduino output pin while a normal relay usually requires the arduino to drive a transistor which would switch the relay coil on or off.

Keep in mind for either of these 120vac switching methods you can't use the arduino analogWrite() command as the PWM output is incompatible with either device. So dimming stuff for 120vac devices takes a more specialty device.



So dimming stuff for 120vac devices takes a more specialty device.

Here we go;-

Solid State Voltage Regulator (AC)

You could find a ton of them here


SSVR input;-

1. 470K-500K pot
2. 4-20 ma current
3. 0-5V 
4. 0-10V
5. pwm

The pwm model is rare. for arduino best bet is 0-5V.


Thank you very much.  I saw those controllers and I wondered if that type of device would work.  Everyone above has been very helpful.  You cannot realize the 'shot' of confidence I get when I actually see that an idea I have may work.  You are 'tops' in my book. 
Gene Ulm

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