Greenhouse Computer Version 2

Work in progress...

Well, the previous greenhouse computer could report the temperature, barometic pressure, and humidity, but it didn't control anything, and the electric fan heater's thermostat wasted a lot of electricity during the previous winter, as it wasn't accurate, and the greenhouse got warmer than necessary.

The greenhouse needs to be kept above 5°C, to keep the citrus plants that over-winter in it alive, but not much warmer, and the fan heater doesn't have any decent form of regulation.

Anyway... Here comes Version 2 of the greenhouse computer. The three boards are, starting at the bottom of the stack,

• A Raspberry Pi 3B+
• A Relay card with four mains relays
• and a Pi Sense HAT.

The problem you get with putting these units in a case is that the Pi warms up the air in the case, so the Sense HAT gives false temperature readings. In Version 1 of the computer, there was a fan blowing air from outside the case onto the HAT's sensors, and that's what I'm doing in Version 2. The fan has just gone in, but I still need to put trunking to direct its air stream over those sensors.

You can see a nice long camera lead on the left, so the camera can go in a separate case. The mains wiring feeds mains to a couple of sockets on the back of the case, one for the heater, and one spare. The relays switch the sockets on and off.

More to follow...