Hand Hygiene

This a link to an IR encoder/decoder kit. The price range is $4-6, depending on how many are bought. This appears to be for transmitting coded information. We could possibly get one of these circuits working and see what happens when the IR wave is interrupted (i.e. someone walking through a door).

http://www.rentron.com/remote_control/TINY-IR2.htm

Developed a preliminary circuit schematic using EAGLE. Our goal is to eventually have this on one board, so both the encoder and decoder are together. Loose connections go to the mote, and are labeled so. In the original circuit, a Panasonic part, the pna4602m, was used for the IR detector. We already have the tsop36238, and will try using this in testing, as these are both detectors for 38kHz signals. Both the encoder and decoder chips use a 5V Vcc signal, but their operation under 3V (two AAA batteries) can be tested.

The ciruit does not work with the tsop36238, and the pna4602m requires at least 3.5 volts. Because the refrence voltage must be at most 3V, we are switching to the tsop32238encoder. This has a reference voltage that goes a low as 2.5 volts. Using a voltage divider with the pna4602m to cut this signal to 2.5V, the decoder circuit is still functional.

With the current circuit, as it is wired, the output period at the pins on the decoder is 54ms. Some pulses are a bit hairy, but when no signal is detected from the LED, the signal goes to constant high, or constant low. I believe the reason for the hairy output signal on the decoder is because the circuit is meant to send coded data, where here we are just using it to see if a signal completes.

On the encoder, the reference voltage the pins are plugged into is a square wave with a period of 14ms. The reason for the oscillationis because if plugged into a constant reference, the bit pattern will only be transmitted once, and we want it sent continuously.