Relay Shield power

Can I just connect a USB wall charger to the Spark Core mounted on the relay shield to power it up or is it necessary to have a 9V DC input ?



I looked into the Relay shield schematics and the 9V power supply is basically used to supply +5V to the :spark: core, as well as to the Relays.

So, you don’t need the 9V power supply in order to use the Relay shield, but just make sure that the USB Power supply has sufficient Amps due to the relay coils being current hungry :wink:

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@kenneth​lim​cp thanks. I am using a mobile charger which is 850mA This should me more than enough right ?

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I am currently using a 500mA USB charger for a Spark Core and a Sainsmart 4-channel relay, so 850mA is probably enough.


Hi :smiley:
As I’ve read about power supply for spark core and reading the notifications of some mobile charger it says output 5V 500mA so does that mean if I want it to use I can only supply the core through usb and due to the 500mA not through VIN pin ??

Are you asking about power supply of the core or the relay shield?

The topic says relay shield power…

Anyways, if the USB supply is 500ma like you mentioned, you can simply connect via USB.

Vin is usually for external supply with a higher voltage or for some other reason you need external source

Yup I saw that subject, obviusly posted in wrong topic :smiley:

Well with couple of testing, relized that the question was dumb :smiley:

Btw thanks for your previus replay :smiley:

OK, I give up. I have spent the better part of an hour trying to determine what the power jack (plug?) size is for the Relay Shield. I see the part in the bill of materials, but I fail to find definitive dimensions for it. I thought this would be obviously available in the description of the product, but if it is, then I missed it. Anyone know what size it is?

Opps I measured in the morning but forgotten to post. 5mm diameter jack :slight_smile:

Thanks much! So I’m assuming that maybe the jack/plug is this one:

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Definitely looks like it! The form factor is different though

Excellent point! For that reason, I don’t think that the product is the right connector. The Relay Shield BOM ( says the manufacturer is Kaweei, which Google seems to link to this manufacturer (, but they don’t appear to publish dimensions for the jack. Thanks again for your help!

I have a photon relay board that when I connected the power it lit up for about five seconds then all lights went out.
I was using an ac/dc adaptor 8.4v450mA.
What do you suppose happened?


We don’t have enough information to know what happened.

When you say “photon relay board”, do you mean a Photon plugged into a Particle Relay Shield?
If it is something else, please let us know exactly what it is.

We need some more information on your setup. Can you provide a diagram showing how everything was wired up when this happened?

One thing you can try is to remove the Photon from everything else and then plug only the Photon into USB power to see if it works that way.

Let us know how far that gets you, then we can narrow down towards what happened.