BEAM Pieces is a BEAM
I used to oscillate, but now I've
Storing energy for a rainy
At the heart of most solar-powered robots is a circuit
called the solar engine (variously called Solar
Engines, solarengines, SEs; a.k.a,relaxation oscillators).
The purpose of a solar engine is to act like a power
"savings account" -- a small trickle of incoming energy is
saved up until a useable amount is stored. This stored
energy is then released in a burst, in order to drive some
useful (if only sporadic and incremental) work.
The solar engine has a number of advantages:
- A solar-powered robot can be made to work, even in
relatively-low light levels.
- Solar cell size is minimized
- Saves money
- Saves weight
- Allows room for the solar cell to be
Four types of solar engines have been built to date:
- Type 1 - voltage trigger. This is by far the
predominant form of solar engine, since they are
"efficient enough" for most uses, and pretty simple to
- Type 2 - time trigger. These aren't terribly
efficient, but are handy for 'bots that need activity at
- Type 3 - charge curve differentiated (i.e., it
triggers when the charge rate of the capacitors slow
down). These are theoretically the most efficient, though
type 3 designs are still in their infancy.
- Nocturnal -- These solar engines charge up
when it's light, and discharge (i.e., power a load) when
Since solar engines are strictly circuits (and generally
just a part of a BEAMbot's circuitry, at that), I've got a
whole section of the BEAM
Circuits Library devoted to more detailed information on
For more information...
Ivar Thorson's writeup on solar engines
(particularly handy since it includes efficiency
comparisons for various designs) is here.
The excellent BEAM-robotics-Tek writeup is
Ian Bernstein of "BEAM-Online" fame has a
writeup on 1381-based solar engines here,
and a tutorial on how to free-form this kind of