Re: Solar Cells Won't Turn Motors

[Glenn Wittrock <spamproof@pluggedin.ca>]

The small permanent magnet motors you are using are going to be highly
efficient at a specific rpm range and rather inefficient at other speeds
especially at start up.  You may find that adding a beefy capacitor will
enable the solar cell to store the requisite starting current to move
the motors.  For kicks how about use battery parallel to start the motor
and see if the solar will carry it after that.


David Dymaxion wrote:

> I'm helping my son do a science project for school. We decided to do
> a small toy electric car powered by a solar cell. I have seen little
> kits for this, but wanted to do it by scrounging for fun.
>
> I've tried various solar panels and motors, but it boils down to
> this: I can't get the motors to turn at all, not even in free air! I
> feel I must be missing something fundamental but don't see what.
>
> Anyway, the little PC fan motor is spec'd at 0.080 amps and 12 volts.
> Solar cell shows 12 Volts and 0.25 A on the multimeter, right on spec
> -- motor won't turn. Tried a little hotwheels motor (4.5 V) -- motor
> won't turn. Tried a small 1.5 V motor from Radio Shack -- motor won't
> turn. All the motors spin rapidly when a battery is applied.
>
> A second solar cell was spec'd at 1.5 W, and the motor at < 1 W.
> Still doesn't turn. (By the way, this solar cell was just $10 at
> Harbor Freight, on sale today.)
>
> I was thinking maybe voltage or current drops precipitously under
> load (Voltage was an open circuit measure, and current a closed
> circuit, low resistance measure). But it can't droop too bad, or
> these things would never meet their claim to charge car batteries.
>
> Any recommendations would be appreciated! What do the little kits do
> that I am not doing? They certainly have smaller solar cells, but at
> least those cars presumably move!
>
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--

Glenn Wittrock

Linux: when you need to run like a greased weasel.