How to make a working windmill model?

How to make a working model on the working of a photovoltic cell?

• Answer:

  A working model using a photovoltaic cell, as it is not possible to make a photovoltaic cell at home etc. These are the things to consider: The voltage per cell is about 0.45 volts, so to get enough voltage several cells may have to be connected in series. A white LED needs almost 4V to operate so would need about 9 cells. A red LED needs perhaps 4 cells. Series means a daisy chain or string, with + to - of each unit except the two ends, so there is a plus and minus wire coming out of the ends of the string. Cells need to be in full sun to work effectively. The light in a room is only a small percentage of their output (so tends to be disappointing). The current from a cell is proportional to the strength of the light, and the size of the cell. A postage stamp sized cell will be very limited in what it can drive. You can find the current rating for the cell you buy in its data sheet (or ask the supplier, or measure it by shorting it with an ammeter when fully illuminated). Whatever you want to operate will need a certain voltage (number of cells in series) and a certain current. It may also need to be connected the right way around. A multimeter can be very useful for testing things. Get someone to help you. Here are some ideas: LEDs of various types. They need to be connected the right way round. You will need sufficient cells connected in series to get the voltage needed. If they can deliver more current than 30 milliamps they need to have a series resistor between the cells and the LED, of perhaps 100 ohms. There are variations on this idea, with combinations of LEDs. Look up LEDs to find more info, or ask another question. A very small electric motor driving something or other - just a paper disc will do for a start. This is a good idea, as it will not be fussy about voltage and current or direction. The vibrator motor from an old mobile phone is a good one to use. Motors from old battery tape recorders are another. A torch bulb. The cells will need to have enough voltage and current to drive this. Four or 5 cells, 100 to 500 milliamps, depends on the bulb. There are kits from hobby and electronics stores which combine a few cells and a motor with a small model. These could be a good starting point. A radio, if the cells are 100 mA or more in size. You need enough to make 6 or 9 Volts depending on the radio, and it could damage the radio if connected the wrong way around. The cells connect to the radio instead of the batteries.