Monday, April 4, 2011

Im blogging again

So after a reasonable hiatus in which I have done many, many things (including building and moving into a new house - yay) I'm going to start writing about stuff again.

In keeping with the amateur electronics-ey theme of this, my first post back is going to be all about the venerable MQ-3 Alcohol Gas Detector that I picked up a while back after reading some articles about it on hackaday and various other sites.

I picked a couple up from Little Bird Electronics (whom I highly recommend) as well as handy-dandy carrier boards:
http://littlebirdelectronics.com/products/alcohol-gas-sensor-mq3 and
http://www.pololu.com/catalog/product/1479 (i cant seem to find this on little-bird anymore though.)

It's pretty easy to wire up your own circuit which mimics the carrier board, but the carrier board makes life even easier. Ignore what the data-sheet says and use a 1k resistor (I think the datasheet says to use 200 or something, but I could be horribly, horribly wrong on that).

Solder your MQ-3 onto the carrier board - it turns out that there is no polarity so you can solder it on any way you like, and it'll just work. Add the resistor and a pin header to make life easy:



I bent my pin-header out a bit to make blowing in it easier - especially when cables are connected. Also there are 2 sets of spots that you can connect your resistor to. It's a bit hard to see, but if you look at the traces, it makes exactly 0 difference which set you connect it to.

Now the other thing I hear about the MQ-3 is that it needs to be 'burned' in. It has a little heater in it that runs off +5v. After turning the MQ-3, it needs to heat up. In normal use this should take around a minute to warm up and the reading to stabilise, but I read around the traps that you need to plug it in and turn it on for 24-48 hours to make it work more betterer (this is, I'm assured, a technical term).

Coming next: Ardunios, shift registers and 7 segment displays!

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