Found at: http://www.he.net/~imagesco/index.html SOLARENG.txt _________________________________________________________________ Solar Engine _________________________________________________________________ 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. _________________________________________________________________ [INLINE] _________________________________________________________________ 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. _________________________________________________________________ [INLINE] FIGURE 1 _________________________________________________________________ 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. _________________________________________________________________ [INLINE] _________________________________________________________________ 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. _________________________________________________________________ [INLINE] _________________________________________________________________ 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 Home Page
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