Wednesday, December 10, 2008

Opto-interrupters for Breath

Recap:  "Breath" is a breath-over-IP phy2phy system.  You blow on one fan (anemometer, whatever you want to call it), that data is sent over IP to the other side where a fan it turned on to match how strong you are blowing on it.  It was inspired to some extend by Scott Snibbe's "Blow Up".

At first I thought I'd do a "half-duplex" solution with a single fan being both the anemometer and the powered fan.  Unfortunately, it takes a lot of wind to blow a case fan around.  I discovered that if you take the coils out of a fan, it spins much easier!  Which lead me to a "full-duplex" solution of one gutted fan as an anemometer, and another as the actual fan.

To measure the anemometer, I started out with an NTE3100 slot-type opto-interruptor, using a piece of aluminum from a can to slide through the slot:

Using a slot-style opto-interrupter

This had the advantage that the NTE3100 available at Fry's.  The disadvantage was that the aluminum bit takes up excess space and could get bent.


We all know that Radio Shack isn't what it used to be, but guess what, they still carry 276-142 "Matched IR Emitter and Phototransistor".  So I mocked them up on a breadboard with the Arduino to ensure it was dependably reading over the distance required:


IR Emitter, Detector, and Arduino


IR Emitter (looks blue to camera)


IR Emitter detector pair and fan

Next step:  I need to get another NTE2987 (N-ch, logic level FET) from Fry's.  I also need wire wrap sockets from Fry's so that I can stick an Arduino ProtoShield in between the Arduino and the Ethernet Shield.  Then just solder it all together and do the software!

Also I may move up from a gutted fan to a real anemometer impeller (with jewel bearings, etc.)

2 comments:

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tolerance said...
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