Aug 14

Shapeways plastic IR permeability / opacity

Cat Faucet IR Sensor

Been working on producing a replacement for the Sharp IR distance sensor I’m currently using in the Cat Faucet. Sharp has declared end of life for that part. Sure lots of places still have them available, but at some point in the future, they’re going to disappear.

One of the big issues with building an IR sensor is the case. You really have to be able to optically separate the IR transmitter from the IR receiver in order to kill any cross-talk. One path I started going down was using Shapeways to produce a plastic case similar to the Sharp IR distance sensor.

I did the 3D model and then had two printed up. one in white strong and flexible and one in black strong and flexible. I figured the white would probably be too IR transparent, but figured I’d give it a try just in case. I had high hopes for the black strong and flexible.

Got’em back and neither worked. Using an old camera w/ the IR filter removed, you could clearly see both the white and black plastic cases ‘glowing’ when the IR transmitter turned on. So toss those in the trash…

Went back to Shapeways and looked at other materials. Turned up their Metallic Plastic which is a Nylon Plastic filled with Aluminum dust. Not much more expensive then the white/black strong and flexible material. So ordered a case made with that.

TaDa! looks like the metallic plastic is pretty IR opaque. Wow and in fact I’m getting like 6 foot detection distance, I was expecting 2 foot. gotta go back and look at that now…

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