I had some time to play with some circuit designs and found this fun LED follower circuit using a 555 timer and a 4017 decade counter IC. I had never used this IC before and saw a similar circuit online and wanted to see how it works. Basically it has output pins for 0 to 9. A clock pulse increments which of the 10 pins is high. I am only using 8 of the 10 outputs on the 4017 with #8 (9th pin) tied to the reset pin which resets the chip back to pin 0 being high. The IC has an overflow pin which goes high on rollover so you could cascade several of these chips to count 10s, 100s, 1000s.
To keep it simple I made a fixed frequency on the 555 timer. Since only one LED lights at a time I tied all LED cathodes (-) together and wired it to ground through one 220 ohm resistor.
I got 10 boards from JLCPCB for $5 plus $20.14 shipping. The components total less than $1 per board so total per board is less than $3.50. It is hard to tell from the photo but I tried the new purple board color JLCPCB offers. It looks great.
You can see the public domain files at https://oshwlab.com/lohmeyer.keith/heart-follower
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