A friend of mine reminded me of a cheap source of electronic components that can be used in robots. And the best thing is you can find it in every supermarket/mall. So a while ago I bought an AirWick FreshMatic iMotion air freshener (the big one), that comes with 3 AA batteries, and a huge can of deodorant included for around 6 eur. The nice thing is that it has lots of useful stuff inside. And not only inside, I think it could be a great robot body as well. It's almost begging to be made into a robot. :)
So what you'll find inside is this:
- one PIR motion sensor on a pcb labeled Smart motion A-06 with LED all nicely connected to a 9x2 pin connector (there are 2 identical rows so there are 9 different connections)
- one motor that should run on 5V, the best thing is it is already mounted on some frame to hold the gears and the motor in place. Wow! I have to buy another one, so I'll have 2 motors, maybe I'll even made it into a segway-style balancing bot (the body seems right :))
- couple of switches, one is soldered to the PIR motion board the other is on a connector (could be quite useful fur plugging into a breadboard maybe) and two other connectors, one to the motor, and other to the battery.
I was really surprised of how nice it is made. Everything on connectors, and so clean. For example in cheap toys you usually see a mess inside. But this is so well made. I couldn't believe it.
So to get to the PIR sensor I was most interested at, I just disconnected everything, unscrewed a couple of screws and that was it. I could easily trace where the power lines go on the board, but I wasn't sure of which pin gets me the motion signal. I googled the name of the board and found some instructables on how to make it work with the smaller version of FreshMatic, but nothing on the bigger version. So I googled some more and found a guy with exactly the same sensor board and also using an arduino that already figured it out. Nice! So it turns out that the pin 5 from left is signal and also that you control the onboard LED by grounding it. So I had connected +3.3V to pin 1, GND to pin2, then we have GND of onboard LED on pin3 and signal on pin5. The tricky part to using the onboard LED is that you control it with sending it a LOW signal to turn it on, and have to turn it into an input pin when you want to turn it off, because sending it a HIGH signal would just make a short. Anyway, the link to the blog post of the guy (thanks man!) is here: http://outroot.com/blog/2010/01/10/airwick-motion-sensor-pir-with-an-arduino/
He's also got some better pictures I think, and a link to the arduino sketch for the AirWick iMotion PIR that he wrote. I abstracted it into a library and got rid of all the delays and made it a bit more useful for me. :) It works great on my quadruped. :) If anybody is interested I can post it here when I'm finished with it (got some things to decide how I want them to be, before I post it online).
If you can choose which version of Airwick you buy, buy the larger one, it has a bigger (stronger?) motor, and it's easier to connect. Although the small one has an aerosol valve or something, so maybe that's useful for someone too. Saw somebody make a flamethrower :D somewhere on the web.
There are other brands, that usually have cheaper sensors (not PIR, but that might be ok), so you might want to check what you'll get before getting one.
With the prices of PIR sensors in robotic web shops (not to mention there's a geared motor inside and 3 batteries, almost half of a robot :)) I think you can't miss by getting one of these and taking it apart :) Also if you're in a hurry and you need your sensor or a motor ASAP, you know where you can always get one.