Parts and tutorial suggestions for Photon with LED, piezo, and coin battery

Hardware
1

Hi there, I’m a software developer and I’m just dipping a toe into the hardware world with the Photon. My project is to turn on an LED and play a sound on a piezo speaker that’s triggered by a url request. I’ve got all the programming done and it’s all working on my Photon kit.

I’m trying to make the footprint as small as possible, so I’d like to have the device powered by a coin cell battery. I’m looking at this coin battery holder:

But it seems like most coin batteries only put out 3v and I need at least 3.5v to use the VIN pin on the Photon.

Are there any tutorials on how to power a Photon with a coin battery? Do I need a power shield or is there a simple conversion I can do on my own?

Also, the piezo is not loud enough for what I want, and the LED is not bright enough. Are there any parts suggestions for louder, brighter options? This is the buzzer I’m using:

And the LED is just one that was packaged with the Photon kit.

Thanks in advance!

Keith

2

@kaxline, I hate to say this but coin cells won’t provide enough power to keep the Photon on for very long. Since you want to trigger the unit via an URL request, the Photon’s WiFi needs to be ON and listening all the time. This is not a low power situation. Furthermore, you want to turn ON a bright LED and play a tune on a speaker so it can be loud, both of which are not low power. You may want to reconsider how you power everything or whether a Photon is the right choice. You could look in to the Bluz BLE Particle variant.

3

Ah, OK, thanks for the feedback @peekay123. I have a couple of follow up questions:

I only need the battery to last ~two hours, does that change you opinion of the power source?

Also, I see the Bluz uses a sleep strategy to wake up a loop every 100ms. Could I employ something like that with the software I flash to my Photon to conserve power?

Thanks again!

4

You should check the max power output of the coin cells to make sure they are capable of supplying the current the Photon can consume when connecting to Wifi + powering the sensors. If it can not supply the required current the voltage will drop out and cause the Photon to reset.

5

Thanks for the help everyone. For anyone else coming across this, here’s a message that @rickkas7 sent me:

"Unfortunately the Photon is not well-suited for running off a coin cell battery, say a CR2032 lithium battery. There are a couple reasons:

The battery only has a capacity of around 150 mAh. In normal operation, the Photon consumes about 80 mA, so it might just barely make your 2 hour window, but probably not also running LEDs and making sounds.

Also, I worry about the peak power output of such a battery. The Photon can consume short bursts of up to 430 mA. This is way above what that battery is normal provides.

Finally, a Lithium coin cell battery is 3.0V maximum, and discharges to about 2.0V as it is used. The Photon requires a minimum of 3.0V, so you’d need two batteries in series to handle discharge. However 6.0V from two new batteries in series is above the recommended maximum of 5.5V for the Photon VIN input, so it’s not an ideal fit.

We generally recommend using a 3.7V LiPo rechargeable battery with the Photon, though that might be too large for your application.

And as a final note, the Photon is not approved as a wearable device. It’s not that it could not be certified as one, but because of the expected use of the Photon, we never attempted certification.

If you’re going to be working in a small area, within 50 feet or so, you might want to consider the devices from Bluz.io. The Bluz is like a Photon but it uses Bluetooth LE instead of Wi-Fi. The Bluz is designed to operate off a coin cell battery for extended periods of time. It uses the Particle ecosystem and can be programmed using the same tools and use the Particle cloud.

I hope this is helpful,
Rick"

I ordered a Bluz DK with a Power Shield that takes a coin battery and a Gateway to connect it to the internet. This seems like the right direction.

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