circuit that uses a
MC34164 voltage trigger that allows most of the capacitor energy to be
used for the motor.
cut pieces of an old PC board for a base. Mount sticky feet
on the bottom.
Mount your components to the board by using the solder pads for
The solar engine in
this artbot uses a mosfet to dump stored energy to the motor.
A MC34164-3 senses the voltage across the capacitor C1. When the
voltage reachs 3 volts, the mosfet is turned on. To allow the mosfet to
remain on till most of the energy is discharged, a capacitor at the
gate keeps the mosfet on to .2 volts. The diode D1 prevents the
capacitor from discharging after VS1 goes high. After VS1 goes
low, leakage through the diode will discharge the gate capacitor and
turn the mosfet back off. Trimmer R1 sets the trigger
voltage. R2 is a pull-up resistor that turns on Q1 when VS1 is
Scope waveform showing voltage across
capacitor C1. Useable range 3.8V to .2V