Relais jumping off when enabling external power supply


So I have 3 relays thath are being controlled by an arduino uno
Im controlling 1 heatingresistor and 1 motor using 2 of the relays and 1 LED-strip using the third relay.

The consuming components are all powered by an external power supply (LED-strip -> 12V) (Heating-resistor 24V) (Motor 5V). And the relays are powered using arduino uno

The LED-strips work just fine. But when I upload the code to let the other 2 work the (2) relays jump off. So only the LED-strip works.

Whenever my external power supply is off the relays work (I can see the red LEDs wich means on). But when I turn the external power on the 2 relays jump off (Heating resistor and motor).

What does this mean??? They are connected exactly the same as the LED-strips..

Also my code is right since its 3 lines wich only set the relays HIGH. ( for testing )

I also have scheme's if you would like them (just ask).

Thanks in advance,

Post the wiring diagram for the faulty version. Post the code using code tags. This is told in the first topics like "How to use this forum" etc.

const int relay_1 = 4;
const int relay_2 = 6;
const int relay_3 = 2;

void setup(){

pinMode(relay_1, OUTPUT);
pinMode(relay_2, OUTPUT);
pinMode(relay_3, OUTPUT);

void loop(){

digitalWrite(relay_1, HIGH);
digitalWrite(relay_2, HIGH);
digitalWrite(relay_3, HIGH);

Here u go

Scheme's -> 1 - Album on Imgur

That link is not redable. Top diagram, no power to the controller. Rewrite the circuit You have made.
With that simple code things are seriously wrong in the powering.

The arduino is powered using USB, this is not included in the scheme.

The code I send was just for testing the relays nothing more. (KY-019)

That is exactly the way to go, as a start or for trouble shooting. Excellent!
Have You tried operating just the 3 relays, without any load connected to them? Then we can check just the low side of the relay circuitry.

Still, please write a wiring diagram of Your circuit. Is there any breadboard involved? If so, how/where, is it used?

yes, I have tested them without a load, they all turn on when there is nothing connected. The only scheme's I have are the ones I am send you wich are made in fritzing. What software do you recommend for scheme's?

I am also using a breadboard.

Also thank you for your replies!


Please read the post at the start of any forum , entitled "How to use this Forum".
OR,148850.0.html. ,

It will show how to attach and post an image.

Thanks.. Tom.. :slight_smile: