Page 98 - Robots Androids and Animatrons : 12 Incredible Projects You Can Build

5.23 Schematic of receiver circuit with digital display

The IR link discussed in the next few paragraphs combined with the
PIC microcontroller outlined in Chap. 7 will allow users to program 77
communications between mobile robots for games like tag and
follow the leader.

Adding a digital display
If reading binary numbers is too cumbersome, we can add a digital
numerical display. The output from the chip may also be fed to a
binary-coded-decimal (BCD) to 7-segment decoder chip, such as
the 7448. The 7448 IC is connected to a 7-segment display like the
MAN 74 (common cathode). These two chips will provide a digital
readout (see Fig. 5.23).

Testing For testing purposes connect the output from the 5089
chip (pin 16) to the input of the G8870 chip, using either a keypad
or dip switches to generate the DTMF signals. The receiver will
display the output via the LEDs or segmented display.

Adding IR transmission
Once the DTMF chips are operating properly, it becomes a simple
matter to connect the chips via an IR link. The output of the 5089
chip is connected to the base of a common NPN transistor (see
Fig. 5.24). A high-power IR LED diode is connected to the emitter

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