# Electromagnetic energy harvesting designing problems

We designed a very simple energy harvester made of a little magnet that moves inside a coil.

We have a vibrating environment moving at 12 Hz with 10 millimeters peak-to-peak. Our pcb will be attached to the vibrating table and will be potted to avoid problems to the components soldered onto the pcb.

Currently only a gyroscope, an accelerometer and a bluetooth module are on it.

The problems derived from the rectification are not the major issues.

Our PCB has to be attached to this vibrating table, that works 24/7. We realized that our energy harvester has to support ca 14 millions vibrations in just two weeks.

I'll assume your "10 mm amplitude" is peak to peak. The position can therefore be described as

P = 5 sin(2π12t) [mm]

or

P = 5 sin(ωt) [mm], where ω = 24π

The velocity is the first derivative of position:

V = 5ω cos(ωt) [mm/s]

The acceleration is the second derivative of position and the first derivative of velocity:

A = -5ω2 sin(ωt) [mm/s2]

Plugging in our value of ω, the maximum acceleration is

Max A = 5ω2 mm/s2 = 5(24π)2 mm/s2 = 28,400 mm/s2 = 28.4 m/s2 = 2.9 g

3 g isn't that much. Of course you have to consider that this will be applied repetitively, but still, it should be possible to design something that can withstand many many 3 g cycles.

• Thank you very much. The amplitude I was wrongly talking about is peak to peak, I'm going to update the post. My second question is: what measures should we follow to get this energy harvester to last two years 'always on'? Commented Jan 13, 2016 at 12:32
• @Three: That's a mechanical engineering question. Commented Jan 13, 2016 at 12:44
• Do you think I have to move the question or make a separate one? Commented Jan 13, 2016 at 12:46