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SOLARENG.txt

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                                Solar Engine
                                      
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   The solar engine is an on board power plant for BEAM type robots,
   sometimes called living robots. The circuit is simple in function. The
   main components are a solar cell, main capacitor and a slow
   oscillating or trigger circuit. The solar cell charges the capacitor,
   until a predetermined voltage is reached, where the trigger circuit
   dumps the stored electrical power from the main capacitor through the
   main load (usually a high efficiency motor). The cycle then repeats.
   
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   The inspiration for this solar engine came originally from Dave
   Hrynkiw from Canada, who uses a similar design to power a solar ball
   robot. I liked the electrical function so much that I decided to
   design my own solar engine. In doing so I was able to create a new and
   improves circuit that surpasses the efficiency of the original circuit
   by about 100 %.
   
   Figure 1 is the schematic for the solar engine. Heres how it works.
   The solar cell charges the main 4700 uF capacitor. As the capacitor
   charges voltage level of the circuit increases. The UJT begins
   oscillating and sending a trigger pulse to the SCR. When the circuit
   voltage has risen to about 2 volts from the main capacitor, the
   trigger pulse is sufficient to turn on the SCR. When the SCR turns on,
   all the store power in the main capacitor is dumped through the high
   efficiency (HE) motor. The motor spins momentarily as the capacitor
   discharges then stops. The cycle repeats.
   
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   FIGURE 1
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   The solar engine circuit is simple and non-critical. It may be
   constructed using point to point wiring on a proto-typing bread board.
   A PCB pattern is also included for those who want a neat looking
   project.
   
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   High Efficiency Motor
   
   Not all electrical motors are High Efficiency (HE). For instance the
   small electrical motors sold at your local Radio-Shack are low
   efficiency type. There is a simple way to determine if a motor is a HE
   type. Spin the rotor of the motor. If it spins smoothly, and continues
   to spin momentarily when its released its probably an HE type. If when
   you spin the rotor it feels clunky or there is resistance it probably
   a low efficiency type.
   
   Caveats
   
   The solar cell used in this circuit is a high voltage, high
   efficiency. Typically solar cells supply approx. .5 voltages at
   various currents depending upon the size of the cell. The solar cell
   used in this circuit is rated at 1.5V but I've seen it charge a
   capacitor up to 2.5V.
   
   I'm sure some people planning to build this circuit are already
   thinking about adding a few more solar cells to speed charging. While
   one can stack low voltage solar cells in series to reach a usable
   (2-2.5V) voltage, one should not add solar cells to increase the
   current. There's a reason for this, in order for the circuit to
   recycle, the current through the SCR must stop (or at least be very
   minimal), for the SCR to close. If too many solar cells are added
   there will probably be sufficient current to keep the SCR turned on.
   If this happens the circuit will stop cycling.
   
   The solar cell used in the circuit is balanced for proper operation.
   
   One component you may want to change is the main capacitor. You can
   use one of the super caps available to store more electrical power. Be
   aware that when using these capacitors it will take that much longer
   to cycle.
   
   Uses
   
   The circuit may be used in many novel and innovative ways. It may be
   used as an on board power plant for a solar racer, to supply power to
   a HE motor for robotic locomotion, audio graffiti, flashing LEDs or as
   the demo circuit here describes spinning an American Flag.
   
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   Parts List
   
   (1) UJT6401
   (1) SCR MCR101
   (1) 22uf Cap
   (1) 4700 uF Cap
   (1) HE Motor
   (1) Solar Cell
   (1) PCB
   R1 100K 1/4 watt
   R2 4.7K 1/4 watt
   R3 2.2K 1/4 watt
   
   Kit contain all the above parts $ 18.00
   
   Available from:
   
   Images Company
   PO Box 140742
   Staten Island NY 10314
   (718) 698-8305
   
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