So what if we’re halfway through 2024? People who needed to fidget all along still need something to do with their hands. So why not hand them a solution with your information on it?
Not only will this spin nicely, the spinning action will use magnets to energize PCB coils and light up LEDs for some persistence of vision action. Designing the PCB was easier than you might imagine thanks to KiMotor, a KiCad plugin to automate the design of parametric PCB motors.
Mechanical testing went pretty well with the bearings and magnets that [mulcmu] had on hand, along with a scrap PCB as the sacrifice. Although a bit difficult to hold, it spins okay with just the bearing and the shaft. Once the boards arrived, it was time to test the electrical side. So far, things are not looking good — [mulcmu] is only getting a few tens of mV out of the rectifier — but they aren’t giving up hope yet. We can’t wait to see this one in action!
Hurry! This is the last weekend to enter the 2024 Business Card Challenge! Technically you have until Tuesday, July 2nd, but you know what we mean. Show us what you’ve got!
How much Energy can be stored in a rotating PCB the size of a bussines card?
Given: Google’s suggestions for a single 13 m/s flick on an outside corner of a standard 0.089m×0.051m business card made of PCB weighing 0.888 kg/m²
Find: KE
Using: KE = ½Iω² , I = 1/12 M (a²+b²)
Find KE
M = 0.089m•0.051m•0.888kg/m² = 0.004kg
KE = ½[(1/12) M (0.089²m²+0.051²m²)][(13 m/s / sqrt(0.089²m² + 0.051²m²)]²
= ½ • 1/12 • 0.004kg • 13² m•m/s²
= 0.028 Joules
Enough to light one LED drawing .02 Watts for 1.4 seconds given impossibly perfectly efficient conversion of KE to EE.
Tape your business card over a Target gift card. You’re welcome.