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Pushpin Computing
Responsive Environments Group

Four-way Infrared Communication Module

The four-way infrared communication module consists of four IR transceivers, one facing outward in each of the cardinal directions. Although the transceivers used are fairly directional, a diffuser made of sandblasted polycarbonate tubing helps to create a more omnidirectional communication range within a plane. The receivers are all multiplexed together into the Cygnal module's UART RX line. The transmitters are all wired directly to an inverted version of the Cygnal module's UART TX line.

Schematic Diagram

Printed Circuit Board Layout

Parts List for 100 Pieces
Vendor Vendor Part # Qty. $/Unit Description

Newark 83F8851 400 $3.29 IrDA transceiver.
Digikey H2258-ND 100 $1.10 9-pin 1mm pitch header for connecting with the processing module.
Digikey P???GCT-ND 400 $0.02465 0603 ???Ohm resistor used to determine intensity, and hence range, of IR transmission. Recommended range is 100-1000 Ohms.
Digikey P100KGCT-ND 200 $0.043 0603 100kOhm resistors used to form a voltage divider, the characteristic voltage of which identifies this communication module as a Four-way Infrared module.
Digikey PCC???CT-ND 100 $0.33 ???pF ceramic capacitor for determining the baud rate at which this module is able to receive an infrared stream. Specifically, the duration of a single infrared pulse should be 10kOhm * CpF, where C is the value of this capacitor as measured in pico Farads.
Digikey 311-0.0GCT-ND 300 $0.02365 0Ohm jumper.
Digikey P10KGCT-ND 300 $0.02465 0603 10kOhm resistor.
Digikey MM74HC221AM 100 $0.4208 Monostable multivibrator for properly conditioning the signal generated by the infrared receiver. Guarantees a uniform pulse width for signals that would otherwise be too short.
Digikey 296-1095-1-ND 100 $0.3300 Single inverter reverses signal polarity of the processing module's UART transmit line for compatibility with the infrared transmitter.
Maxim MAX4634EUB 100 $1.28 4:1 multiplexer for switching between IR receivers.

Last Updated: 01-DEC-2004
MIT Media Laboratory