Spark Relay Shield Weirdness

I had this problem before and I thought I had solved it, clearly I didn’t. I’m using relays 1 & 2 only 3 & 4 are not being used. When I apply power to the shield, even if a spark core isn’t attached relay 3 is triggered. I hear it click and the red light is on. Any thoughts on why this might be happening?

They input signal is pulled-down and should not be behaving that way.

Can you monitor the Voltage on D2 (which controls relay 3) and see if there was a voltage change during boot up?

1 Like

D2 or D5? I don’t see a D2 on the schematic.

It goes like

Relay 1 - D0
Relay 2 - D1
Relay 3 - D2
Relay 4 - D3

Ive read this on the forum somewhere before.. i just cant remember where! when the core powers up the pins aren't initialized until the users program runs.. after it connects to the wifi and cloud.

This guy has a interlock so nothing gets effected during power off and boot up.

1 Like


like i mentioned in the previous post, there is a pull-down resistor on all the input to the relay signal.

So there’s no reason for a random trigger since the pull-down is available.

That’s why, i’m suggesting to monitor the voltage on the input pin during power up. :wink:

Sorry i didn’t read the question properly… or your reply… just trying to help while still half asleep!

If its happening without the core in the shield its very strange… maybe R9 is faulty or has a dry joint?

1 Like

Ha! Clearly no one sleeps around here. I’ll check the voltage either tonight or over the weekend and let you know.

1 Like

Power the relay shield without a Spark Core attached. If any relay turns on, try grounding all relay input signals one at a time (D0, D1, D2, D3). If any relay is on solid after this, the NPN transistor is probably shorted… or there could be a solder short on the board near that component.

1 Like

Well I’m not really sure what to do, I powered it up without today to test it out and relay three stayed off this time. It seems to happen mostly when I start messing with the board. Once my next spark core gets here I’ll be able to play without having to remove this board.

1 Like