Public Lab Research note

Thermal flashlight -- now with more LEDz!

by donblair | February 15, 2014 17:55 15 Feb 17:55 | #10042 | #10042

What I want to do

I'm trying to generate a circuit board design for Public Lab's thermal flashlight project.

I'm using a fairly easy to find and inexpensive LED on the board -- but there was a concern that it might not be bright enough -- so I added three more! :)

If this isn't sufficiently bright, we might consider having a ring of LEDs around the entire board, perhaps?

I'm still learning Eagle, and this is my first attempt at adding what is called a 'ground plane' -- which makes routing easier, and generally helps to smooth out electronic noise in the system.

My attempt and results

Here's the latest schematic:


It's got:

  • four RGB LEDs -- all controlled by the same pin, and wired in parallel (perhaps in another version we could control all the LEDs separately?)
  • a 32u4 Arduino-compatible microcontroller
  • a footprint for a screw terminal and resistor that would allow for the addition of a thermistor (for use in the thermal fishing bob use case)
  • a buzzer (for a cool geiger-counter like temperature effect -- or play a wintry tune if the temp gets too low)
  • a holder for a coin battery, and a connector for an external Lipo battery -- both of which can be recharged on-board if the device is plugged into USB power
  • two analog input / output pins have been broken out
  • and RX / TX is also available (in case you want to interact with the board via a Raspberry Pi)

Questions and next steps

I'm going to look over the design files on github, see if I've goofed anything up, and then aim to order a test batch. If anyone out there knows Eagle and can review the design for any obvious flaws -- or has suggestions for improvement -- please do chime in!

Why I'm interested

I want to see if I can make a prototype before SNOWFEST so that we can see exactly how effective igloos are as insulation against the Vermont weather.


It's going to be 40° F on Thursday, Friday, and Saturday, so if you want to collect environmental data inside the SNOWFEST igloo, the RIFFLE might be a better tool.

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