MicroPower Solar Engine:  Voltage-Controlled Solar Engine: Ken Huntington's fairly complex, but very efficient "micropower" solar engine design. No 1381s or ICs needed.   (added 11/05)

Miller Solar Engine:  Voltage-Controlled Solar Engine:  This is a slightly more-sophisticated design based on a 1381* voltage discriminator.  (added 11/05)

Photovoltaic Switch disables unused LEDs:  03/18/04 EDN Design Ideas  /  (added 1/05)  In many applications, it's desirable to disable LEDs used for system verification. Many options are available for the disabling function, including manual SPST (single-pole single-throw) switches, enhancementand depletion-mode MOSFETs, bipolar-junction transistors, and JFETs. The circuit in Figure 1 automatically disables the LEDs when a mechanical housing encloses the circuit card, thereby ......

PM1 Solar Engine:  (circuit / design added 8/03)

Portable Solar Battery Charger:  (circuit / design added 8/03)

PowerSmart Solar Speeder V2:  This must be the most efficient bipolar transistor motor driver design for this application and I recommend it for the solar roller competitions. A 1381E is used to trigger at 2.4V. While it takes a total of 10 components plus motor compared to the stock circuit's 6 components, you will clearly get better performance compared to a stock Solar Roller/Speeder circuit.  (added 11/05)

Remote Solar LED Light:  (circuit / design added 8/03)

RF Transmitter Light Sensing:  (electronic (schematic / circuit added 4/02)