Freesteel Blog » New datalogger ready for impact

New datalogger ready for impact

Wednesday, March 23rd, 2016 at 6:16 pm Written by:

Final late blog of the day.

An end-to-end design in Kicad all by myself, which was then cut out beautifully on the triangle machine tool.



Soldering, laser cutting and 3D printing took up the following week, and it should now small enough to fit onto the glider without getting in the way.

(Tom’s trick of defining a virtual second side of the board which we don’t actually cut, but instead implement with jumper wires worked a treat.)


We’ve got the questionable barometer, GPS, humidity, 2 temperature sensors, wind meter and an absolute orientation sensor (at the top) all logging at high frequency to an SD card and with an OLED screen to show me what’s not working so I can fix it in time. The black slab at the bottom holds 4 AA cells.

First thing that got logged was my fridge over last night using a string of 5 temperature sensors left over from Housahedron days:


It’s the most boring high efficiency fridge in the world with a cooling cycle of four hours and, not surprisingly, different temperatures on each of the glass shelves.

I’m wondering if the new microbit device, of which a million will be distributed to children, has enough tech in it to use as a fridge logger. Everyone has a fridge. This would make an easy project for kids to log and upload the data of their make and model to a common place in order to find where the crappy fridges are. In the future they need to all be found and replaced, because they cost significant energy and CO2, but nobody knows since the electricity bills are aggregated for all appliances in one house and are mostly unknown.

For contrast, here’s an overnight log (interrupted at 4am in the morning for my host to get up and drive to London) of a fridge in Leeds using a different datalogger where the cycle is four times an hour:
I can’t explain the long hiccup at 3am where it skipped 3 cycles. Maybe there is a lot of information in that particular curve, such that the real way to find out about the quality of the fridge is to turn it completely off and measure how warm it gets overnight. Great idea. I can see a lot of kids getting into trouble over that one when the food is all spoiled. To which they can respond: “Hey look, it’s only the fridge. It’s not like I’ve done it to the whole planet.”

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