←back to thread

Ask HN: Most interesting tech you built for just yourself?

1901 points l2silver | 1 comments | 27 Apr 23 15:04 UTC | HN request time: 0.219s | source

Maybe you've created your own AR program for wearables that shows the definition of a word when you highlight it IRL, or you've built a personal calendar app for your family to display on a monitor in the kitchen. Whatever it is, I'd love to hear it.
Show context
altered_state ◴[29 Apr 23 10:48 UTC] No.35751748[source]▶
In my new house with underfloor heating, an air source heat pump was installed that turned out to have a controller that switches it on and off over 80 times per day which reduces its lifespan significantly. I decided to see if I could improve on this so I started reading lots of papers regarding temperature control.

Since this is a tricky problem to solve, I built a quick fix solution while I work on the "real" version. The quick fix measures the average indoor temperature in the house using zigbee sensors and uses a number of weather forecast APIs to calculate the amount of heat lost from the house in a day based on the difference of outdoor / indoor temperature and the amount of solar irradiation. It runs at midnight and creates a 24h schedule based on the forecast energy price and expected COP. The heat pump is controlled with a relay from an ESP32. The algorithm/app runs on a raspberry pi and is written in Rust.

It worked surprisingly well last winter with some tweaking needed during very cold periods. And the heat pump only switches a few times per day now and makes very long efficient runs, theoretically greatly increasing its lifespan and simultaneously reducing my energy bill.

I'm still planning on building the better version I had planned based on a thermal model of my house, but that will require more studying and now that the quick&dirty version works so well the pressure is off a bit.

replies(3): >>35752158 #>>35764323 #>>35770867 #
sgarland ◴[29 Apr 23 12:09 UTC] No.35752158[source]▶
This is fascinating, but what is the temperature swing in your house?
replies(1): >>35755909 #
1. altered_state ◴[29 Apr 23 18:56 UTC] No.35755909[source]▶
Interesting question! The swing is about 0,5 to 1 degree C (1 - 2 degrees F) over the day. If it's very cold out the controller makes sure to spread out the heating in a few blocks during the day instead of a single block at the most efficient timespan.

So it's much less stable than with the original PID controller which kept the temperature very stable, but surprisingly it doesn't bother us, proved by the fact that WAF is high. Which to be honest I did not expect.

I still have plans to improve on it by modeling the temperature drop in the house and making sure it stays within certain bounds. But that is for "later".