Anybody will to help out with electrically related 5th grade science project (1 Viewer)

[workingdog]

My son and I had this great idea to make a little power generating windmill for his 5th grade science project. I found plans online - some PVC tube, some magnet wire, some really strong magnets, and some popsicle sticks and cup up solo cups for the wind vane and a little 1.5 volt light bulb. What could go wrong?

Well, spinning the magnets in the pipe with windings around the outside of the pipe is producing no power at all on my voltmeter. If it were weak, I'd understand, but I'm not understanding why I'm getting nothing.

I've cleaned the ends of the magnet wire and checked for continuity. I can't think of what it might be.

 

[e9999]

5th grade is above my pay grade, but where exactly did you put those magnets and this wire, and how? Could the windings be oriented in such a way that things cancel out?

 

[workingdog]

that's what I was wondering? We used two magnets for more power, but maybe they are cancelling each other out.

We are going to try again today with just on magnet.

These are neodymium disc magnets

 

[thegadgetguy]

Interesting project. I'm not an eletromagnetics expert, but here are a few thoughts **accuracy not guaranteed**:

• Your waveform will be AC, not DC, so make sure you have your meter set correctly. Depending on what meter you have and how fast you are spinning the magnet, you may not be able to get your frequency output within the range of frequencies that your multimeter can read. If you can get to at least 50 Hz, it's a safe bet you should be able to read that. f = RPM/60
• Magnets should be in the "stuck together" configuration if you're going to use two.
• You might also check the resistance of your coil and compare it to a similar length of magnet wire that hasn't been installed on the PVC pipe to make sure your coil hasn't shorted out. You could also figure out what it should be using an online resistance calculator and the wire gauge if you don't have any more wire to measure.
• Have you confirmed that nothing happens when you hook the light bulb up?

That's all I got. Post up if you get it working!

 

[workingdog]

Well, one problem is that I've been looking at DC on the meter. I hadn't groked the difference. I'll try AC now and see what I get.

Yes, we cannot get the light bulb to light. If we use a little hobby motor, and spin it with a drill, we can get the bulb to light.

 

[ducktapeguy]

Its been a long time since my last physics class, but I believe your setup is wrong. For DC the coil of wire should be in between the magnetic field, and there needs to be a way to switch the polarity of the field in sync with the rotation of the magnets (or vice versa depending on how it’s setup), otherwise you end up with a very weak AC current like gadget guy mentioned. I can’t tell by the picture the way the poles of the magnet are oriented, but if you connect a battery to the wire do the magnets orient themselves to the magnetic field? It looks like you’ve essentially created a weak electromagnet. Also, even if you get it working it’s more than likely that the amount of power you will be able to generate from this might not be enough to light even a small bulb. An LED might be better, but I don’t know for sure, but they will light up at much lower currents than a regular bulb.

 

[workingdog]

Ducktapeguy - I think you are right. We got it to work. I found an online source that helped. You need like 200' of wire and you generate weak AC. We got about 5v to 6v AC from the thing. We tried with a little light bulb and immediately blew it up. Then we tried LED (found some that go on at less than 1v) and it lights on one side of the AC pulse. So we hooked a second one up and it lights on the other side. Ended up being an interesting demonstration of AC current to watch them alternate. Turns out the design at the original web site we found, some STEM web site, was totally wrong and worthless. But, we got something to work. Good enough for the science project.

We also got a little 12v hobby motor to work too, but it will barely light the little light. So i bought a better quadcopter motor to use as a back up, but I can't figure out how to make it generate power. But, we're good, so nothing's hurt but my pride.

 

[wapitimud]

A DC motor should be the same electrically as a DC generator. Ensuring you aren't using a step motor, servo motor, or anything too odd, this should come easily without needing to build the dynamo from scratch. I assume you are likely using very small DC motors, which might be sized appropriately for this job.

Stick to DC, it makes things a bit easier.

I would expect for a windmill, at least as I see commercially, for the rotation of the propeller to be fairly lowspeed.. the rotation of the generator likely needs to be relatively highspeed. I think commercial windmills use significant gearing to work, and you may need that as well.

Perhaps you'll have to rob a gearbox from a toy car. A visit to a local garage sale or a thrift store is in order here.

You should be able to cheat, and test your potential DC motor on a vice, powered by a cordless drill. Speed that up, and repeat your results on the windmill/gearbox.