Powering Core and attaching a relay unit [SOLVED]

Hey all, new here and new to using the Core.

I’m interested in making my Core battery powered (for which I’ve purchased a battery pack that holds 4x AA batteries), while also attaching a mechanical relay unit to control some other devices.

So, my noob questions:

  1. Battery pack should be attached to VIN and ground, correct?
  2. When I was using the relay unit on my Arduino UNO, the VCC on the relay was attached to VIN on the Uno. How should I connect to the VCC if I have the battery pack connected to VIN?

Thanks, just want to know that I’m not going to burn out my hardware.


What voltage are you getting out of your battery pack?
If your voltage is around 5volt, then yes, attach it to VIN.

Is your mechanical relay unit, just a relay, or a board with the relay(s) on it.Since it has VCC it is probably a board. Then yes, connect the VCC to the VIN voltage.

Yes, around 5V.

and yes, on a board.


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@blindelephants, can you be more specific on the relay board (model)? Relays notoriously create power spikes when they are energized so a large (47uF or more) electrolytic capacitor between Vin (+ on cap) and GND (- on cap) on the Core is recommended. Also a small (0.1uF) decoupling capacitor should also be placed between the Core Vin and GND (as near as possible).

The 4xAA batteries will present 6V to the Core regulator which is the maximum it will take. However when their voltage drops below 3.6V, the regulator will no longer function, something to keep in mind.

Hare you planned your battery power consumption given that the Core consumes more power than an Uno? :smile:

I think it will be a bit less, if using rechargeable nimh.
AND quite a bit MORE if using 14500.

Yes, but has the OP mentioned them?


With these (NiMHs) the available gross energy output and hence battery life will be even less than with alcaline.

@blindelephants, a good point has come up. What type of batteries do you plan to use?

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The OP stated that his power pack was putting out close to 5volts.

I tested my Core, and it kept running down to 2.6 volts on the Vin .
When does your Core stop? @peekay123. I assume your Core will run until Vin is 2.6 volts also, so I don’t know where 3.6V comes in ?

The OP said the power pack is providing about 5 volts.

I’m using 4 alkaline AA’s, output should be more around 6 volts.

Got it working. I’m using a Sainsmart 2 channel solid state relay

Seems to be working fine in this setup.

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@blindelephants, Great. glad to hear it is working.
If you think this thread is solved, you may want to edit the title, and add [SOLVED] to the end of the title.

Have a great day, and if you have other questions, you are welcome to ask.

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