Four-way Infrared Communication Module

Description
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
[PDF]
[Protel]

Printed Circuit Board Layout
[PDF]
[Protel]

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.