With the recent surge in Omicron cases, shipping may be slower than stated times. We are working to build, ship and respond to everything as quickly as possible. Please see all COVID-19 updates here. Thank you for your continued support.

Member #1265635

Member Since: January 16, 2018

Country: United States

  • Hi all,

    I now have one flight under my belt and thought it might be useful to share the result of the internal heater as I was provided with excellent information from this blog before flying.

    I went with a 3.7v rechargeable 18650 battery with a capacity of 2600mah, it did a stirling job powering the heater. The heater comprised of a power resistor as described in the blog and I made a 'radiator' from a coke can. Aluminium is the light, thin choice and radiates heat very well. Just want to point out that Coke didn't sponsor this flight! A TMP36 temp sensor monitored the internal payload temperature, whe it fell below 2 degrees, the Arduino switched on the heater via a relay, anything above 4 degrees resulted in the heater turning off. Freezer tests and flight data showed a nice even temperatrue between 2 and 4 degrees. The payload box was inch think polystyrene.

    Happy to supply pictures/further info if anyone would like that.

    Best wishes


  • Appreciate the reply Nate; thanks for the pointer on wire thickness too. As an aside (it may be useful for someone), when the USB cable was powering things, I got a small voltage drop on the TMP36 when the relay coil energised. To test things, I was asking the Arduino to switch the heat pad on when the TMP36 reported >22 degrees (so I could test it on the kitchen table with my finger as the heat source). The voltage drop caused the calculated temp to drop under 22 degrees and the relay switched the heat pad off. This cycle continued until the increase in temperature was great enough to be above the 22 degrees even when the voltage dropped.

    I tried capacitors to no avail then had the bright idea of using the battery (which is how things will be powered in flight) and it worked fine...no voltage drop so no yo-yoing of the temperature. I then plugged the USB cable back in (leaving the battery attached) so I could see what was going on via the serial monitor and that worked fine too.

    Best wishes


  • Hi, great blog, thanks. I'm learning electronics from the ground up so please bear with me!

    Is there any significant advantage to using the load controller rather than a simple temperature sensor, (in my case, a TMP36)? I have been testing a heat pad powered separately and controlled via a relay from the Arduino. This switches the heat pad on and off depending on the internal temperature of the box. I like the idea of the resistor as a heater so will be testing that too. Additionally, should I use a thicker, stranded wire to connect the resistor to the battery?

    Be interested in your thoughts.

    Best wishes


No public wish lists :(