Power supply for photon project

A partner and I built a pet food dispenser for a project for school. We are using a mg958 servo to open a valve to allow the food to be distributed. The power supply I ended up using to power the servo was a 6.5V 2500mA. It works the servo just fine but I would like to somehow power the photon from the same power supply so there is only one cord to plug in. I was wondering if anyone had a recommendation for reducing the current/voltage to a usable amount for the photon?

Here is a 2.5Amp 5v power supply used for the Rasberry pi.

Is that to much input current for the photon?

Current is not pushed into the device, as long the voltage is suitable the Photon takes as much as it needs, no more no less :wink:
So the power supply just has to capable of deliver all the Photon needs and the excess will just lay bare (or be used by other devices).

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@jhypes, your servo is specified for an Operating Voltage: 4.8v-6.6v. At 5v, the torque will be lower and the current draw will be driven by the torque required from the motor. You may want to test your existing setup with the 5V 2.5A supply first to see if the servo can reliably operate as before. The Photon peak at 350-500ma during wifi connections and then settle at 80-100ma during typical operation. If you use the single 5v supply, make sure to filter that supply at the Photon’s Vin pin with both small (0.1uF) and large (100uF) capacitors to filter out servo switching noise.

Another approach would be to use an LDO regulator to regulate your existing 6.5v supply down to 5v for the photon. An LM117/1117 or other low dropout regulator able to supply 500ma would work nicely. Again, the same capacitor filtering rules apply. :slight_smile:


That helps a lot. I wanted the 6.5V to handle the servo. I think I will regulate the power supply I have. Thank you for your help.

Would it be better to filter the input voltage to 5V and put it into the Vin or to 3.3V and supply it to the 3V3 pin?

@jhypes, if the Photon is providing 5v to any devices via Vin, then regulating to 5V is needed. Otherwise, you could supply the 3V3 pin with the proper regulator.

Makes sense. Thank you so much.

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I think I understand your question… you definitely do not want to power the Photon directly from the 6.5 volts… it will NOT take well to that! I had a similar issue and I found a handy D.C. regulator at pololu.

This is the link https://www.pololu.com/product/2850

It takes anywhere up to 38 volts and regulates it down to a perfect for photons 5 volts.

Hope this helps.

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