Steve's Things

So, since I’m really bored I decided to build a device that tracks ambient temperature and light levels. While this may not seem very interesting, I suspect the relationship between the two, while not directly linked, will be interesting especially when placed outside. Well, I suppose I’ll put a few pictures up and outline some of the stages I went through to get it to this point.

1. Prototyping.

The initial version of the sensor, using older stuff from viscometer project.

This didn’t take long. I already had a board with a single supply opamp (JRC 7014D) on it that was already set up for the LM335Z temperature sensor. I used a bread board, as can be seen in the picture, and used a messy bunch of wires coming from the PICKIT2 to the MCU. I chose a PIC16F684 for this job since it has some analog channels and it doesn’t have too many pins.

2. Checking it out. In order to see if the Voltage range will allow for freezing temperatures and room temperature, I had to test it with some snow.

Cup o' snow to check and see if the Opamp is biased correctly

Temperature check with the IR gage

The voltages swung just fine with a bit of extra range. I have about 50C to work with in range, good enough.

3. Making the board. For this I used a board from measurexplorer. I have tons of these but haven’t had much luck using them. The only ones that have worked well for me are the ones with 3 holes per pad. Anyways, here are some pictures.

Start of prototyping the board

Finished Sensor board with both light sensing and temperature sensing

Anyways, This board took me a couple hours to make but it works well and required no rework, thankfully. You can see both the LM335X (TO-92) and the CDS for sensing the light. This board interfaces to an RS232 board that I’ve made and that I use for some of my other projects.

4. Getting ‘er running. While the unit itself is already programmed in terms of the MCU. it needs some adjusting for voltage on the pot and that’s about it. now to affix it to something so it doesn’t move around.

RS232 and Sensors glued to a board

Tracking it on the computer

As you can see, I simply used hot glue to affix both the RS232 board and the sensor board to the block of wood. Its a temporary arrangement while I come up with a good enclosure for outside. I brought my old laptop out into service for this project, works well just for collecting data.

Anyways, here are some images of some collected data.

Living room temperatures (click to see description)

Basement (click to see description)

Well, so far so good. Now I’ll make the enclosure for outside and improve the sampling. hopefully I can leave it out all spring/summer and see the patterns.