Relay8 channel current limits

Got comments, questions, or tips about any of the shields listed on Post them here!
Post Reply
Joined:Sun Feb 23, 2014 7:41 am
Relay8 channel current limits

Post by thefarmer » Sun Feb 23, 2014 8:12 am

Hi folks,

This might be a simple one. I have a Relay8 shield mounted to an Eleven. I am controlling two 12VDC Finder relays using two channels on the Relay8. The relays are controlling two solenoids for a sprinkler system. I chose 12VDC relays because I wanted to pass the 12VDC power source from the Eleven through to the Relay8 via VIN thus not needing to use the external power source terminals (instead using the little jumper to connect VIN to the relay channels).

After hooking everything up and programming the Eleven, channels 1 and 2 on the Relay8 started off fine for about 20 seconds until a distinct popping sound came from the shield. Now channels 1 and 2 don't work, the little red LEDs just glow and I get all sorts of random voltage readings from those channels. So I thought I would confirm my suspicions by trying the same program and wiring on two other channels 6 and 7. They both popped as well.

After consulting the Finder datasheets for my relays it seems that the relay coils only require 86mA @ the recommended 12VDC. My question is why do these relays pop the channels on the Relay8 when the channel limits are noted as 115mA per channel?

I've since fixed the problem by splicing into the Eleven power source and running 12VDC to the External power source terminals on the Relay8. Has worked faultlessly without ruining my last remaining channels on the shield! Lucky I bought the shield with 8 channels even though I only needed two channels!

Even though my problem seems fixed, does anybody have any idea why this was happening?

Thanks heaps.

Freetronics Staff
Freetronics Staff
Joined:Sun Jul 14, 2013 7:06 am

Re: Relay8 channel current limits

Post by andrew » Sun Feb 23, 2014 9:22 pm

Sounds like you have a faulty shield. If you'd like a replacement please email

Post Reply