Sunday, May 17, 2015

Make: Electronics Experiment 23 part 1

Experiment 23 of Make: Electronics uses 74LSxx chips (TTL chips) instead of the 74HCxx (CMOS) that has been used in previous experiments. In the first part of this experiment a simple binary counter in made (figure 4-102). I ordered some low current LED's especially for this experiment to be able to see the output of the circuit. The circuit, with three binary output pins connected to a LED, can count from 0 (000) to 5 (101).

I encountered no problems building the circuit and with the low current LED the output was clearly visible. The only detail that puzzles me is that the 74LS92 counter has a Clock input B (pin 1) and Clock input A (pin 14). The output from the 555 chip (pin 3) is connected to Clock input A nevertheless Clock input B needs to be connected to Binary output A (pin 12) of the 74LS92 counter. Anyway everything works fine.

Breadboard with the binary counter. The 74LS92 counter (left) is triggered once every second by the 555 chip. The three LED on the left indicated the output from the counter.

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