Rob A's (Im)personal Blog.
Rob A's (Im)personal Blog :: Solar Roller #1
- Panasonic BP-24221 Solar Panel
- Type 1 solar engine using FLED in series with
diode for trigger level
- 2x 16V, 4700µF capacitors in parallel
- Cassette player motor, direct drive
- Freeform construction
- 3 wheel - 1 direct drive wheel (cassette player
pulley), 2 free rolling (cassette tension
- perfboard frame, fuse holder motor bracket
- <$20CDN (including $9.00 for the cheap
This was my first attempt at a solar roller. I first
breadboarded the solar engine circuit, and played with the
trigger voltage and discharge resistor values to get the best
performance out of the (rather inefficient) motor I had.
Initially, I only used one 4700µF capacitor, but once built, I
had to add a second cap in parallel to get enough torque from the
motor to move the roller.
I left the solar panel on long leads so I could angle it to
remain perpendicular to the light source. This turned out to be
unnecessary as the performance was so poor anyway.
The frame is horribly unsymetrical. I tried mounting the motor
in various places, but found no matter what I had to
counterbalance the roller by placing the solar engine and
capacitors off to the opposite side. I also experimented with an
outrigger type design for balance, but couldn't get it to go
straight when the single drive wheel was too far off center.
From this angle it doesn't look too bad.
I built the solar engine between the leads of the
capacitor, which determined the size. The pinch rollers
make great wheels - easy to attach and low friction. The
perfboard construction is quite light and easy to shape.
It started out rectangular, but I cut out unused pieces
to try to keep the weight down.
This side view shows the construction of
the solar engine and the way the motor is mounted. I used
a couple of drops of superglue to hold the motor in the
spring clip because it kept springing out. The high
center of gravity made balance extremely important, as
the whole device is quite tippy.
This top view shows how visually
unbalanced the whole assembly is in order to physically
balance it on the single drive wheel. As well, you can
see the untrimmed leads from the second capacitor. This
makes it look untidy, but reuse is simplified. Self
tapping screws were used to attach the fuse clip to the
- Form follows function! Balance and structure can be much
more important than solar engine performance.
- Torque is important! Even though the motor would make
over two rotations per pulse (with two capacitors), the
roller would only move about 5mm per pulse. It took very
little to stall the motor. The roller would often get
stuck on bits of gravel and small irregularities in the
concrete outside. When this happened, the roller would
just rock back and forth without moving. I added a
10,000µF cap in parallel to the existing two (using clip
cords), and the stalling problem stopped, but charge time
Last Updated: May, 1998