Make: More Electronics

Chapter 19. Experiment 19: Decoding Telepathy

Take a look at Figure 19-1, where I have redrawn the Telepathy Test logic diagram using a decoder chip. Although this circuit now incorporates every possible feature that I talked about earlier, it requires only three chips. A circuit doesn’t get much simpler than this.

Decoder Testing

So what is this mysterious component that makes everything so simple? Before you build the circuit, let’s start by bench-testing a decoder. The one I’m recommending is the 74HC4514. I’m specifying the HC family because whenever I buy a chip, I’m thinking that I might reuse it for some other purpose in the future, which may require it to power LEDs (at least while testing the circuit). Remember that the 74HC00 chip ...