IR Object Detector

Note: This device is part of the XNET home network system. See the page on Home Networking for how to power and interface to this device. Any modifications, such as to rework it as a 'stand alone' device are up to you.

This unit uses one TSAL6100 IR/LED emitter from Digi-Key. This IR diode has a narrow (10 degree) radiation pattern at 940 NM. It is driven via 2n2904 transistor for maximum current pulses. The detector is a Vishay TSOP4838 38Khz integrated receiver module. The 38Khz signal for the emitter is generated in software.

Here is the idea: Send out a 38Khz IR signal and look for its reflection off a nearby object. Both the emitter and detector are optically and electrically isolated from each other to minimize self actuation. Additionally, the pulses are sent out only at certain intervals and the PIC only looks for the signal at the end of the output burst.

This device is demonstrably immune to most stray activation. It has a 25% greater range at night than in full sunlight.

 

The entire unit is housed in a standard low-profile single outlet electrical box with a blank faceplate drilled out for the emitter and detector.

Note that the emitter and detector are optically isolated using heat shrink tubing.

 

The designation of this device is 'G1'. It responds to the following commands.

/G1Pn - Set pulse count for IR transmission.

/G1R - Read pulse count setting.

/G1V - Return version number.

The number of pulses generated on each 38Khz burst is adjustable. Setting the pulse count to 7 provides the minimum sensitivity and anything over 15 is the maximum.

This unit automatically transmits code '/C1G1<cr>' over the network to the Clock/Console device (C1) indicating the detection of an object (by G1) within its range (8-10 feet).

 

Here are the Source, Object, Layout files.