Power Supply for Relay Shield

Does anyone have a recommendation for a wall wart to power the relay shield? I tried using an old Compaq laptop power supply that is rated as 18V at 1.9A. The diagram on the power supply indicated that the center was + and the barrel was -.

When I plugged it in I got a curl of smoke.

Unfortunately, at this time I don’t have a volt meter. I have ordered one. It should be her in a few days.

I think this similar to the power supply that I used for my relay board.

12VDC, 1.5A (18W), Barrel Plug, 2.1mm I.D. x 5.5mm O.D. x 11.0mm, Positive Center

They’re widely available, so by no means do you have to order it from Digi-Key; I just provided that as an example (and they have full specs listed on their web site).

The specs of the relay shield on the store page do tell this

But the silk and the the docs do state 7 ~ 20V

This might need clarification.
What version of the shield have you got?
Was the Photon plugged in correctly?

Additionally to voltage and polarity the DC “quality” (ripple & noise) might play a role too.

Thanks for the quick answers.

ScruffR, I had not seen the voltage spec in the documentation. I was going by the rating etched on the board. Silly me for believing what I read.

I didn’t have the Photon plugged in at all. I didn’t want to lose the chip if the power supply didn’t work.

Another question I have in the same vein. Can I still use the USB connection to the Photon if it is plugged into the relay shield and properly powered?

Yes, you can.
There is a protection diode that prevents Vin voltage to feed back into USB.


Thanks ScruffR