PV Gap

Fred Said:

if the top of a wire from a solar cell is cut how can i fix it or what can i do to connect it with a motor?

We Answered:

Solder it or get some electrical conductive epoxy for a strong hold

Erin Said:

What kind of voltage regulator for solar cell?

We Answered:

Solar cells have a high output impedance, which tends to produce a constant current. A constant current is one way to charge a cell.

So why not connect them together? I don't think you need a regulator.

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Josephine Said:

On a solar cell, do you need to have a transparent conducting oxide film (TCO) with bus wires?

We Answered:

You need to collect the current. It will work with only bus wires, and you need bus wires to connect to it anyway (ie cant do without)
and yes it works best with both - thats why they are made that waY!

Adrian Said:

Building an LED circuit that is powered by a solar cell?

We Answered:

You must first determine the forward voltage of the LEDs you wish to use. For example red ones will be around 1.6v while green or yellow ones can be 2.0v or so. Next get the spec on the forward current of the LEDs, this figure will usually be the maximum current they can handle so you can go up to this figure or stay below it. You then must find a solar cell or combination of cells to produce the voltage and current necessary for the LEDs.

For example if you were to use 4 red LEDs connected in parallel with forward voltages of 1.6v and currents of 10mA each, you would need a supply to produce 1.6v with a current output of 40 ma. If your solar panel does not exceed 1.6v then you would not need resistors to limit the current. However to get more consistant output from the LEDs you may want to use resistors so the current paths are isolated. In this case you would need a higher voltage output solar panel. The formula below calculates the resistors needed.

(solar panel voltage - led forward voltage)/LED current=resistance in ohms

6v solar - 1.6v (LED)=4.4v 4.4v/0.01A (10ma for one LED)=440 ohms

connect a 400 ohm ( +/- 10%) resistor in series with each LED, then connect the led and resistor combinations in parallel across the solar panel. With the rated amount of light for the panel's specs you should have the correct voltage and curent for each LED. As the light level drops the LED's will glow dimmer. RemeMber that the solar panel's output is highest and rated with continuous wave light ( sunlight ), not the light from a household bulb that is pulsing at 60 Hz !

Clear as mud ? don't worry there is a fudge factor here so you can have latitude in the figures. The above math is merely the ideal solution, not the iron clad rule to make this work.