3 ms·

I bow to both Dima and Charles on making practical physical hack projects! I'm more of a software guy. I guess my biggest hardware project (other than building

I bow to both Dima and Charles on making practical physical hack projects! I'm more of a software guy. I guess my biggest hardware project (other than building a 3D printer from someone else's plans) was in 2012 or so making a PID-based home heating controller using an Uno with a custom perfboard shield with a thermistor for measuring the air temperature and a 433 MHz transmitter for talking to a set of Jaycar 240V remote controlled power outlets to control primarily a 2400W oil column heater, plus a fan pointing at it which I turned on when it was at a high duty cycle. Plus switching the home water heating on and off on a fixed schedule just as a side thing from the same board. I used that in Wellington for 3 winters before moving to Russia for a few years and saved NZ$500 per winter on electricity bills compared to previous years using a mechanical Honeywell thermostat to control the heater.

sitkack 2y ago
That is really cool. Sounds like it could be turned into a great product. It is funny that Nest basically added 3 if statements to a thermostat over a reed thermal switch and became a multibillion dollar company for it.
- brucehoult 2y ago
  It worked really well. That Honeywell thing let the temperature cycle over maybe a 2º C range. I was sampling the thermistor 100 times in about 1/10th of a second (analogRead() on Arduino) and then doing exponential averaging each second with a 32 second time constant (i.e. `temp = temp - (temp >> 5) + new_reading`) and averaging and getting a nice stable temperature reading that moved smoothly in 0.01º C increments. Turning the heater on and off at maximum every 30 seconds the room temp usually stayed within ±0.03 C of the set temperature -- not precise on an absolute scale but detecting and correcting small changes accurately. I was actually thinking of trying to make a product, especially once Flick Electric started up with electricity prices changing every 30 minutes based on the wholesale rate plus a 2c margin. You could (still can) get the current 30 minute wholesale price at your local substation from electricityinfo.co.nz with a simple http query, so you can build something to make intelligent decisions. But then I got a job overseas and dropped the project...

sitkack 2y ago

That is really cool. Sounds like it could be turned into a great product. It is funny that Nest basically added 3 if statements to a thermostat over a reed thermal switch and became a multibillion dollar company for it.

brucehoult 2y ago
It worked really well. That Honeywell thing let the temperature cycle over maybe a 2º C range. I was sampling the thermistor 100 times in about 1/10th of a second (analogRead() on Arduino) and then doing exponential averaging each second with a 32 second time constant (i.e. `temp = temp - (temp >> 5) + new_reading`) and averaging and getting a nice stable temperature reading that moved smoothly in 0.01º C increments. Turning the heater on and off at maximum every 30 seconds the room temp usually stayed within ±0.03 C of the set temperature -- not precise on an absolute scale but detecting and correcting small changes accurately. I was actually thinking of trying to make a product, especially once Flick Electric started up with electricity prices changing every 30 minutes based on the wholesale rate plus a 2c margin. You could (still can) get the current 30 minute wholesale price at your local substation from electricityinfo.co.nz with a simple http query, so you can build something to make intelligent decisions. But then I got a job overseas and dropped the project...