The BEAM Circuits Collection is a
The "FRED" popper
A photopopper circuit based on
circuit is built from two "Fred"
Ben Hitchcock has the following debugging tips on Fred
A) If you can see Fred's eyes flashing (no motor
1) Grab a piece of wire, and connect one end
to the negative terminal on the capacitor.
Put your Fred under a lamp, or put him in sunlight,
until the eyes start to flash.
2) Touch the wire to the base of the PNP
3i) If the motor moved, then the problem is with
the 33k resistor,
the 3.3k resistor,
the 0.22 uF capacitor,
or the FLED connections.
3ii) If the motor didn't move, then the problem is
with the transistor
B) If Freds eyes never flash (no motor movement):
1) Check the solar
panel and capacitor
2) Short out the capacitor,
and then watch the FLEDs
closely. If one flashes faintly, then stops and
doesn't flash again, then you may have a bad motor
3) If this doesn't happen, then go over the whole
robot component by component.
C) If the motor makes funny noises but doesn't
1) Try putting a 1 uF capacitor
across the motor terminals.
2) Try using a physically bigger storage capacitor
(like a 2200 uF 16V).
D) If the motor fires strongly once when you put it in
light, but then is either weakly on all the time or stops
and doesn't pop again:
1i) Your solar
panel is too big. Put some tape across it or put
it inside, to lower the amount of current
it can produce.
1ii) Your motors are too efficient. Put a 100 ohm
across your motor terminals.
2) Send me some of your motors or solar
panels, because you are obviously too rich, and
need to scavenge more (lower quality) parts.
For more information...
Ben Hitchcock, the "father" of Fred,
has a nice tutorial on building a Fred photopopper
his debug tips came from a Yahoo groups post
Ray Diaz has a very detailed Fred photopopper
tutorial of his own here.