driving two clock motors
The Photovore circuit on the previous page drives a modified clock mechanism.
This is the standard mechanism you find in most "ticking"
clocks. It contains a 1.5v cell and a crystal-driven chip that pulses a
"magnetic rotor" once a second. This motor drives a train of
gears to activate three hands.
Clock motors take very little current and can be easily driven from the output
of gates. Here are the instructions for modifying one of these
The circuit for the Photovore by Pitronics described on the previous page
is shown below:
HOW THE CIRCUIT
The circuit consists of a Solar Engine section and only activates the rest of the circuit when the electrolytic
has sufficient voltage across it.
When the voltage is about 4v, the BC558 (in line with the power rail) gets
turned on and the rest of the circuit is activated.
Two NAND gates form a square-wave oscillator and this signal will be passed to
only one motor at a time, depending on the light received by the photo diodes
or the activation of the feelers.
The two gates connected by a 10M resistor form a bi-stable switch that sits in
either a HIGH or LOW state, depending on the pulse received from the feelers or
photo diode. This HIGH is passed to two NAND gates that drive one of the clock
If you need to drive 3-pole motors, the
circuit below should be used: