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Schematics of the GPS IRDA Converter The old version (V1.01) is located here. The following picture gives the design of the GPS IRDA converter at its current state (V2.03). Everyone is allowed this schematic for personal use. This schematics may not be used for commercial purposes. I take no responsibility of damages caused by the use of this schematic. Download a larger version of the schematic here Someone requested me to design a IRda to RS232 converter so the PDA can also be used to download waypoints into the GPS-receiver. You can find the schematic here
The schema is divided into two parts. The left part is a oscillator build around the half of a NE556. At the input the RS232 signal (-12V -> 12V) is removed of its negative voltage by using a diode. If the input signal is serial at 5 volts you can remove the diode but you must than power this schema with 5V. The right part is a single shot pulse generator build around the other half of the NE556. Power supply can be any voltage between 5 and 15 Volts DC (Specs of NE556) Power consumption of the schema is about 20mA. Most of the power is consumed by the IR-led. If the IR-led is installed near the PDA it is possible to change the value to for example 4K7 Ohm to preserve power. The following schema displays the different signals in the schematic.
The first signal is the serial input received from the GPS receiver. A low (= a '0'-bit in the signal) is triggering the NE556 to generate square-waves at a frequency a little less than 4800
Hertz. The square-wave is then fed into the single-shot pulse generator which is triggered on the falling-edge of the square waves. For every falling edge
a 20
μS pulse is generated. The NE556 is able to drive up to 200mA so the output
can be used to drive the IR-led directly. The RC combination of the NE556 is designed to generate 4800Hz pulses for a serial input signal a 4800 baud. Changing the RC combination will allow you the change the baud rate of the schematic. Some people reported that using a 330pF C5 capacitor was not working for them. It seems that different manufactures of the NE556 have different specifications for the entry resistance of pin 8. Try a 1nF capacitor instead. Parts list
PCB Lay-out This is a PCB layout of the GPS IRDA Converter I have designed using EAGLE 4.11. The schematic files and the board files can be downloaded here. This schematic includes the power supply for GPS mouse like a Haicom HI-203E. The additional parts are:
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