Solar Engines 

On this page I shall be explaining various solar engines, along with displaying their respective schematics. Solar engines are very important to BEAM robots, and to me are the the true testament to Biology in robots as it creates self sufficient and 'food' seeking robots.



FLED Solar Engine

THE FLED Solar Engine (click image to enlarge). R1, resistor, 1K to 10K. Q1, transistor, 2N3904 or PN222, NPN type. Q2, transistor, 2N3906 or PN2907, PNP type. FLED, Flasing LED, any fine, red preffered. M, motor, 1 - 6 Volt rating, most small motors found in junk will do fine.

Ok so what exactly goes on in this circuit? The solar cell creates power, the power it creates depends on its spec (power is defined as Voltage * Current). This power alone wouldn't run the motor unless it was a really good solar cell, so instead the power has to be stored in the capacitor until there is enougth to actually turn the motor. If the motor had access to the power which we are trying to store, it would use it up even though it is not enougth to actually create movement. So we have to stop the motor from being allowed to use the power until there is enougth of it. This is where the FLED comes in the FLED will only allow current to flow when the voltage reaches the level appropriate for the FLED being used (see list below). Once this happens the circit will be complete and the motor will be active, however there is no longer enougth power for the FLED to activate as it is being shared with the motor... so the circuit needs to latch on and stay on until all the stored power is used. To perform this function a transistor is activated which bypasses the FLED and so current still flows.

FLED operating voltages:

Yellow: 1.6V (I measured it as this, but if incorrect please e-mail me)
Red: 2.6V
Green: 3.0V



Miller Solar Engine

THE Miller Solar Engine (click image to enlarge). C1, C2, Q1, transistor, 2N3904 or PN222, NPN type. 1381, Voltage Trigger M, motor, 1 - 6 Volt rating, most small motors found in junk will do fine. D1, regular diode

Circuit theory and operation: Basically in the Miller engine we are charging the strorage capacitor until a point where the 1381 voltage monitor detects the voltage that it is searching for. This voltage is dependant upon the 1381 that you have bought:

• C - 2.0V
• E - 2.2V
• G - 2.4V
• J - 2.7V
• L - 3.0V
• n - 3.4V
• Q - 3.8V
• S - 4.0V

When the 1381 'sees' this voltage it will activate, allowing current to flow from pin 1 to pin 3. This causes the base of the PNP to go low, and as such it turns on, allowing the motor to dump power through to ground. The motor continues to dump power as long as the 1381 is held high by C2.



1381 Solar Engine

1381 Solar Engine (click image to enlarge).

Theory of operation: The 1381 solar engine is similar to the miller engine... however here the 1381 triggers, allowing a base current to flow to the NPN transistor. This then turns on as an NPN requires a high signal. When this is on the motor begins to dump power. This allows the PNP transistor's base to go low, and as such provides a continuing base current to the NPN transistor. We have an SCR latch! the latch will continue until there is no longer enough power, at which point charging starts again.