Automatically Charging and Discharging a Capacitor

I'm going to enter a "Solar-powered crane" competition where we need to design a small device that runs off a 1.5V-400 mAh solar cell.

Given that 400mah isnt much in the way of current, I would like to use a capacitor to build up a little more power for the motor to run off of.

My question: is there anyway that I could buy or build a circuit that will automatically repeatedly charge and discharge the capacitor without anyone having to manually throw a switch?
 

vk6kro

Science Advisor
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That rating would be in mA, not mAH, probably.
The mAH rating would be indefinite because a solar cell produces current for as long as it is left in the sun.

400 mA would be the maximum current the cell could produce in bright direct sunlight.

400 mA is not too bad. You can get motors that run on 25 mA at 1.5 volts.

Some hobby and educational stores carry demonstration solar cells with an included motor which will run off the solar cell. These run off a single solar cell which only gives 0.6 volts while your solar device must have about 3 cells in it.
So, they are pretty efficient motors.
They have plenty of power, but you would need to gear them down with pulleys to get realistic rotation speeds.

If you wanted a higher voltage than 1.5 volts, there are solar powered path lights that generate about 3 volts to run a LED from a 1.2 volt NiCd battery. You could hack one of these to get the circuitry that does this.
Or, there is one in this article:
http://www.siliconchip.com.au/cms/A_30709/article.html
but it would be better to just select a suitable 1.5 volt motor.
 
Ah, I thought a "mah" rating didn't make a lot of sense, but that's how they wrote it in the rules.

At this point it's obvious that I don't have a lot of experience with electronics...

I do know there is such a thing as "voltage amplification" but can you actually get more power into a motor if you have a circuit that does that, or am I misunderstanding the concept?
 

vk6kro

Science Advisor
4,081
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A voltage amplifier won't help. That is for something else. I'll explain if you like.

You can step up the voltage with circuits like the ones in my previous post. These produce more voltage for the motor but draw more current from the solar cell than just the motor on its own.

A greater voltage for the motor might mean it turns when it otherwise wouldn't, or it may mean more torque and greater revs.

Don't worry about lack of experience. Nobody here was born knowing this stuff.
 
Ah, okay.

I don't have any problems getting the motor to turn our gearbox with a load on it or anything like that. I'm really just looking for ways to get more power into it.
 

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