This is part of a series of videos in which I try out some experiments from 'Make: Electronics', Charles Platt's excellent introduction to electronics.

In this video, Experiment 18 has me building a reaction tester and introduces us to two new components, the 7 segment LED display and the complementary 4026B decade counter IC.

NOTE: At c.16:00 the simplified circuit diagram incorrectly shows the reset button shorting the supply rails. In the full circuit diagram in the book, you'll see that there is a pull-down resistor in the connection to the ground rail. I'm sorry for the omission here. Please always refer to the full circuit diagrams in the book if you're building the circuit. Thanks to ‪@makerjeff86‬ for spotting my omission.

00:00 - Introduction
00:59 - Counter test circuit demo
03:38 - How the test circuit works
09:56 - Reaction tester circuit demo
12:46 - How to wire multiple counters together
16:28 - Calibrating the circuit
18:35 - Final reaction tester demo
19:07 - Outro

Links to book:
https://amzn.eu/d/cXyVlfW (UK)
https://a.co/d/i11zkxM (US)

If you want to learn more about the 555 timer chip before watching this video, please see the video for Experiment 15:    • Make: Electronics Book Experiment 15 ...  

If you want to learn more about Johnson Counters, there's a article on Wikipedia here: https://en.wikipedia.org/wiki/Ring_co...

You can find further information on the components used in this experiment in Volumes 1 and 2 of the 'Encyclopedia of Electronic Components':
Vol 1: https://amzn.eu/d/1lzEccv (UK)
https://a.co/d/4S3oVfm (US)
Vol 2: https://amzn.eu/d/4QuPQL9 (UK)
https://a.co/d/5wyCFtg (US)

I'm not associated with, incentivised by, or paid the publisher or author, I'm just a hobbyist sharing my experiences of the book.