This entry in the Project14 Techno Toys competition is mainly to boost participation without setting the bar too high.
I don't have a lot of toys around the house that I own, but I did find one that nobody laid a claim on. I call her Sparky.
In this project I am taking a little wind-up hopping toy (Sparky) and retrofitting an LED powered by a power-scavenging circuit.
The power-scavenging transducer is a piezo disk mounted under Sparky's feet, so when she hops, the disk gets flexed and generates charge.
It is not a lot of power given the amount of energy in the 1 mm hop of a toy that weighs 18 grams, but it is enough to briefly flash an LED.
It is pretty cool that the circuit does not need a battery to drive the LED - and the whole circuit and transducer is light enough (about 1 gram) not to prevent the toy from hopping.
The circuit consists of a bridge rectifier, a capacitor, a resistor and an LED - plus the piezo disk:
The circuit components were all SMT parts, except the capacitor, to minimize weight. The construction is space-wired also to save weight.
Tip: Soldering small components like this can be pretty tricky but I stuck them on some tape to hold everything in place while I soldered the parts - it worked great.
The LED was easily visible to the naked eye although not very bright. My camera on the other hand had a lot of difficulty focusing on the chick and seeing the LED. In the video I resorted to turning off most of the lights to see if the LED would show up better. The video did capture a couple of the flashes, but not in focus and it is so dark, it is hard to see the chick.
I think I could improve the power-scavenging efficiency by ensuring optimal flexing of the disk, but the concept works even without tweaking - I didn't play with resistor or capacitor values - literally the first devices I grabbed.
Here is a video of Sparky the Power Chick:
This blog has become more popular than I expected so I figured I better see if I couldn't improve the video. I pushed my camera to its limit and cleaned up Sparky a bit - no more tape.
In the first segment I constrained Sparky so she couldn't hop out of the picture and set the camera to fixed focus. Then I let her hop around, but it is still much more visible than my first video work.
Here is a picture showing the piezo disk glued onto Sparky's feet:
And a couple more images of Sparky all wired up: