Dejan Levec

Central & water heating controller

About a year ago I decided to replace analog heating controller at home with something a bit more advanced. I have designed circuit and PCB at that time, but haven’t made until recently. It consisted of ATmega328 microcontroller, 4 relays and ENC28J60 breakout board for network connection. When I was writing source code, I thought about noisy relays and my distrust to using ENC28J60 (I previous had problems with AVR hanging after too much requests).

I quickly scrapped the plan and started thinking about more reliable approach, something like separating controller logic from network access. That day (or maybe day before) I got 3 MSP430 Launchpad boards I ordered online a few weeks ago. I heard about those boards quite frequently before, but did’t want to jump on that bandwagon = frankly, I didn’t have a good reason for buying it. But when I saw ad or something about it, I said what the heck and bought it. So I instantly saw an opportunity to use it for heating controller in combination with WR703N wireless router.

So my plan is like this:
– WR703N provides web interface, logs statistics in combination with USB flash drive, and fetches temperature from Ethernet temperature module
– MSP430 controls optocoupler-triac board according to temperature sensors, and reports data about current state of sensors/triacs back to router (it should also be possible to put it in a manual mode and circumvent control logic)
– optocoupler-triac board featuring 4 BTA12 triacs controlled by MOC3063 optocoupler

Cost of this setup:
– controller box and PCB: 10€
– WR703N: 20€
– MSP430: 3€
– DS18s20 temperature sensors: 0€ (samples from Maxim IC)
– triacs, optocouplers and similar stuff: < 10€

So for about 40€ I will have a really powerful controller with data logging capabilities.

I need to control 4 devices:
– electric boiler for heating water in summer
– oil burner for heating water boiler and central heating
– pump for heating water boiler
– pump for circulation of water through radiators

Electric boiler and oil burner have additional temperature sensors to prevent overheating of water, so even if my system screws up, it won’t cause any unwanted behavior except a bit warmer water and rooms in the house.

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