The object of your desire will not be able to resist this heart shaped kitsch-o-tron, lovingly hand-crafted on perfboard with a CD4017B decade counter and 555 astable. But you probably can’t go wrong with flowers and chocolates as well. Just to be on the safe side.
This build was not exactly an exercise in meticulous planning. I started out by getting together all the red LEDs I could find and soldering them on a perfboard in artistic fashion. I hadn’t thought particularly hard about how to light them up. There was some vague idea of pulsing PWM using a logic chip with lots of inverters and a quad op-amp. Or maybe pseudorandom outputs from a linear feedback shift register (74HC164 plus 74HC86). Then I counted the LEDs and realized that I had used exactly 10, so I looked in my bits box and found a CD4017B decade counter and a 555 timer chip. There were plenty of schematics on the internet to choose from and I shamelessly ripped one off, adapting it as I went. The diagram below approximates what I did or maybe should have done: in the event, I cut corners by leaving pin 4 on the 555 unconnected and omitting the 10 KΩ resistors.
The hard part was soldering the perfboard without the usual spaghetti effect. My initial intention was to hard wire the chips but I’m very glad I opted to use DIP sockets. To make things neater I used 0805 surface mount passives soldered on the back of the board. It was not an especially expert job but turned out fine, and not too hideous at the back.
Stop by at the Magic Smoke Tindie store to pre-order LED chaser kits, including all the necessary components and a custom-designed heart shaped PCB.
- 5 x 7 cm double sided prototyping board
- CD4017B decade counter/divider IC DIP16
- NE555 timer IC DIP8
- 8 pin DIP socket adapter (3, use 2 for CD4017B; optional)
- 5 mm red LEDs (10)
- SMD capacitors, 100 nF, 0805 (3)
- Tantalum capacitor, 1 uF (or SMD if you have it)
- Trimmer potentiometer, 200 KΩ, single turn
- SMD resistor, 1 KΩ, 0805
- SMD resistors, 10 KΩ, 0805 (2; optional)
- 9V battery clip
You May Also Need
- Electrical solder (rosin flux core, lead free)
- 26 AWG hook up wire
- Irwin self-adjusting wire stripper
- Hakko flush cutter
- Aoyue 936 soldering station
- Glue gun (for strain relief on battery clip leads)
Originally posted on Magic Smoke.