Valentine LED Chaser

Technology
Valentine LED Chaser

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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.

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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.

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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.

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Coming Soon

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.

Materials

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Originally posted on Magic Smoke.

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Tom Price of Magic Smoke Lab: gadgeteer and garage scientist. I am a messy desk person. Away from my desk, I am a messy floor person. @t0mpr1c3

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