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Just a quick update on the progress of the wireless temperature sensor using the DS1631, ESP8266 board, and Openhab.

Hardware

Firstly, I’ve updated the circuit diagram because there were a few obvious mistakes. The updated circuit diagram can be seen below (and in the github project folder).Circuit diagram 0.2

It’s a bit messy, but I hope to clean it up soon.

In order to do some better testing, I’ve created a simple PCB that is small and doesn’t require breadboards to be placed throughout the house. Since I wanted them quick (i.e. I didn’t want to wait over a month for boards to be manufactured in China…), and I don’t have any PCB fab facilities, I used this guy to mill 2 single sided PCB for me. Unfortunately, I designed the PCB with holes that are just a bit to small. As a result, I can’t get my reset button in, but I was able to force the rest of the components through the holes (just). The board layout is shown below.

PCB design 0.2

The two red lines are actually small wires as I couldn’t find a way to design the whole board with just tracks on the bottom (remembering that the PCB was being milled, so I couldn’t make the tracks and gaps too small). In all I was quite happy with the board and it appears to be working well. REMEMBER: If you’re going to use the board layout, make the holes bigger!

Soon I hope to make a double sided PCB with silkscreen, etc. but for now this works well.

Software

There’s not much change to the ESP code. I’ve added a small conditional statement that makes sure the device doesn’t send any numbers if the temperature is over 100C because I was having issues with high temperatures being sent out when the board first switches on (I think this is due to initialising the DS1631 board on boot up).

In order to test the DS1631 boards I’ve made (one on PCB and the other on breadboard) I decided to physically put the side by side and see how close – or otherwise – the temperatures were. Below is the temperature chart over a period of 4 hours.

Temperature variations

As you can see, the two are very similar with a max difference of about 0.4C, which I can cope with easily! Interestingly, the green line is the PCB board and appears to be more responsive to changes in temperature over the red line which was on the breadboard. That might change once the PCB is placed inside some kind of box and mount it on the wall.

Both the Openhab config files and the ESP code have been updated onto the Github project folder.

Coming up

I’m in the process of designing a small double sided PCB for the ESP temperature sensor that will be very small. I will also put the current temperature sensors in different rooms in my house.

I’m also looking at ways to actually turn the heater on and off. I initially thought that my current thermostat was RF controlled, but after taking the front off, it’s clear that it simply has a relay that opens and closes a 240v circuit which I presume goes directly to the boiler.

Therefore I’m going to have to break into the circuit and insert my own relay.

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