Convert perpetual magnet motor output to 5 volt DC

dc motoroutput

Disclaimer: Hi, I was in the neighborhood (StackOverFlow) and just noticed this cool site. I have had this general wondering for a while now and I am not sure if my question is constructive enough for this site (not from EE background). But I am genuinely interested to learn/know if there's any practical use of the concept. So, please do keep an open mind and any explanation would be greatly appreciated.

Concept: Let's say I have a DC motor (12V, 0.5A) and I managed to keep it spinning by "strategically" attaching some neodymium magnets around it (my intention is not to start a war regarding whether or not it is possible, but for the sake of practical usage, let's assume it is possible). The output I am getting is 7-9V, unknown amperage.

Question: Is it possible to convert this variable output to a stable 5.0 volt (standard USB output) with 0.5-1.0 amp to charge cellphone and if so, could anyone please provide some resources / explanation / diagram?

Best Answer

Assuming we can completely ignore the laws of physics, especially as regards conservation of energy, then yes it is possible*.

The device you are looking for is called a "Voltage Regulator", and it takes in a variable voltage and outputs a stable, lower, voltage.

They come in two basic flavours:

  1. Linear Regulator. These are like automatic variable resistors. They constantly adjust how much voltage is dropped across themselves in order to keep the output voltage stable. They are quite inefficient, and tend to get rather hot with higher currents.
  2. Switching Regulator. These chop the incoming voltage up into small chunks by rapidly switching it on and off. The ratio of on to off gives the output voltage. A feedback loop monitors that output voltage and adjusts the ratio to keep it stable. A low-pass filter then smooths that on-off waveform into a single constant voltage again. These are much more efficient because they don't waste the excess voltage as heat, they just turn it off instead.

Now the electronics are sorted out, why not head over to Physics.SE and discuss perpetual motion and why it doesn't work in the real world. :)

* for certain values of "possible"