Am I drawing too much current with my relays?

I am using an UNO board with a 9v 1amp switching DC power supply using the DC input jack on the UNO. I am using the UNO to control a typical four-relay 5v relay module (with optoisolators) designed for connection to Arduino boards. There is no indication of the current draw of the relay board.

I have the UNO powering the relay board and two LED's (each on their own I/O pins with 330k resistors). Thats it. I use two buttons using internal pull ups do dictate which relays turn on when. My project worked perfectly for a while but seems to be degenerating with intermittent phantom button presses and random resets. Most of the time all four relays and both LED's will be on at the same time.

Can the problem be intermittent board failure because I am drawing too much current from the UNO voltage regulator?

If this is the case can I use a buck/stepdown converter on my 9v power supply to control relay board separately at 5v? Does this sound like it could be the problem or am I not overdrawing current from the UNO voltage regulator with my setup? I cannot think of what else could be causing the problem. Again, it was working great and seems to be getting progressively worse.

SImple answer YES you are drawing too much current.

The Relays should have thier own power and a common ground back to the Arduino but not from the live side of the relays.

Bob.

yeah i had similar problems when i tried to use them. those relay modules seem to draw a lot of power.

For future reference for anyone else having similar problems:

I tried a separate power supply for the relay board and it did not fix the problem. What did fix the problem however, was switching to USB port to power the UNO. I originally had a 9v 1amp DC supply (advertised as being designed for Arduino, but purchased from cheap Chinese manufacturer on eBay). I noticed when I plugged the UNO into my laptop for power everything worked perfectly again. So I tried a USB cable with a USB wall charger instead of the 9v power supply and now it works flawlessly. I'm guessing either the voltage regulator on the UNO was going bad or the power being supplied from the DC adapter was dirty. Either way, using USB port to power the UNO fixed the problem and works perfectly even without the auxiliary power supply for the relay board (although I will still use it for good measure).

Yes please do use external power for relays as it is one of the more common topics that come up and if I were to hazard a guess then I would say more than 90% of relay reliability issues are down to the power scheme with a chunk of those also being common ground issues too.

Bob.

Very good point from moses1592. a USB connection supplys 5v. When using the USB jack on your board it bypasses the voltage regulator. So as long as your power plug has a decent amp rating, this approach should help!

ballscrewbob:
Yes please do use external power for relays as it is one of the more common topics that come up and if I were to hazard a guess then I would say more than 90% of relay reliability issues are down to the power scheme with a chunk of those also being common ground issues too.

Bob.

Regarding the power to the relay, I know this has been covered extensively and there are diagrams of how to properly power the relay module but the "proper" wiring did not work on my relay module. Per the diagrams I have seen, when using external power for the relay board, you are supposed to remove the Vcc/JD-VCC jumper and connect the external power to the JD-VCC pin. Then connect the external power GND to the relay module GND, and make sure the Arduino power supply GND and external power supply GND are connected. When I do this the relay board is deader than dead. If I connect the external power to either of the Vcc on the relay board (in place of the +5v from the arduino) then it works. But according to what I've read this is incorrect and bypasses the optoisolation protection.

Side question: When using the DC jack through the voltage regulator, can you simply connect the relay module's external power supply GND to the arduino's GND pin, or must the grounds be physically connected BEFORE the DC input jack? I assumed the arduino GND pin was physically connected directly to the GND lug on the DC input jack, even though it's voltage is regulated.
Am I mistaken here?

taterking:
Very good point from moses1592. a USB connection supplys 5v. When using the USB jack on your board it bypasses the voltage regulator. So as long as your power plug has a decent amp rating, this approach should help!

Sorry I think I posted my last response at the same time you posted yours. :smiley: