Trigger MOSFET or other switch with low voltage from DC Motor

Projects General Guidance
7

Hi @Terrypin

Thank you for the insights. It's a fifth grader project, so it needed to be simple. I believe my girl may have been a little too ambitious with their project. They are not in an electronics class. They touched on the topic of renewables in her science class and the teacher assigned them into groups and have them come up with a model that showcases renewable energy. I also encouraged her to pursue it, when I knew clearly that her, her teammates, the one dad (me) in the entire group (unfortunately) didn't have the skills to properly design it the way they wanted it.

The idea as it was pitched to me was this:

  1. A windmill's propeller spins and creates electricity
  2. 6 LED's should illuminate when the windmill starts spinning
  3. All LEDs should turn off when the windmill stops

Unlike what @sonofcy believes, I'm just an adviser and proving support for what they are not trained to do - like handling a soldering gun. Yes, I could have taught them how to crimp connectors and just plug and play all wires, but they are using my materials (and tools) and I prefer to use the least as possible ( :grimacing: We don't have 2 day prime shipping in Belize; we have 2 months when you're lucky shipping speed).

My girl is her dad's daughter, she is the team lead and she procrastinated for her entire spring break and now she only has till the 17th to present their project. So, yes, now we have a deadline and no time to learn new methods or procure some sort of ready-made kit, which may be against the rules; the team is expected to fabricate everything, but the teacher acknowledges some soldering and use of resistors was required, so we asked and she allowed me to assist with that part. The girls are building the windmill, houses, lamp posts, roads, etc

So, after realizing the motor doesn't generate enough juice, the new idea is this, and I know it is cheating because the LEDs are now illuminating from a battery pack and not from the voltage generated by wind spinning the DC motor. But they already completed their concept essay, and the teacher accepted it, so now they have to complete it. I'm now pitching it to them that, like in the real world, energy generated by the windmill is stored on a battery and that is the reason the windmill has wires leading to the battery pack, and why the batteries are the direct source of power for the LED lights.

So, now, my girl doesn't know yet that what they wanted, the way they envisioned it, is not possible. The reason, why I haven't told her it's because it's too late. As far as they are concerned, the windmill will spin with the aid of an AC desk fan, and the LEDs will illuminate.

My objective, where I need ideas from smarter people than us on this project, is:

  1. This is my motor and propeller (microwave fan) https://photos.app.goo.gl/C1BLCXPcgtfy5Byb8
  2. Like explained in my first post, the highest millivoltage I registered was 840mv. user grb, I was unable to get anything over 1 volt. The minimum forward voltage of the green LED is 2.1v I believe.
  3. The millivoltage detected when the DC motor spins should trigger a relay or switch to close the LED circuit powered by 3 volts. I don't know how to do this.
  4. When the DC motor stops, it should trigger the switch/relay to open, cutting off the battery pack from illuminating the LEDs. I don't know how to do this.

I'm unable to get arduino boards, components, etc. So a simple switch, triggered by millivolts is all we have. If the above is not possible with I may be able to find around here, I'll have to tell the girls that their project will have to become an explainer, where they manually trigger a switch to turn on the LED. I have been trying to think of something mechanical that closes the LED battery-powered circuit the microwave spins (negating the use of a DC motor), and then closes it via some sort of sustained contact when the blades stop. But, I can't think of anything :confused:...