This page is my humble attempt to try and capture the design and evolution
of the BEAM SE. The idea is to try to capture the incremental changes
and mutations from one design to another. This is somewhat similar to
the taxonomy used for biological species. (In this case Intelligent
Design may be more appropriate but don't get me started on that...).
Let me stress again that this not the way these circuits were
It is not a record of the history of these SEs but rather an
exploration for further development of these circuits by using a generalized
approach (to paraphrase Wilf here)
This taxonomic system uses the circuit "mutations" and changes as a guide.
It does not describe the chronological order in which these SEs were created.
One of the things that can be learned from this system is how to combine
ideas, get inspiration for new designs, and perhaps find "missing
I tried to build a hierarchical structure starting from the root design
of the Solar Pock-Mark.
The Pock-Mark is perhaps the simplest circuit that contains all the elements
of an SE, the power source (solar cell), the storage unit (e.g. capacitor)
and the load (e.g. LED, motor), it does not have a latch mechanism.
All sibling designs, have the same colors. Evolved designs are contained
in nested boxes.
There are many other variations that I missed, don't know or simply didn't
know where to put. I welcome suggestions and comments.
Most of the graphics and circuits on this page were done by others, more
talented than I. All the credit goes to them. I have tried to link to
all the sources (click the image to go to the source). I'm sure there
are errors and mistakes, they are most probably mine and not others'.
If you see an error and/or problem please let me know. If I'm using one
of your designs against your wish, please let me know and I'll remove
Proto-BEAM: The Solar Pock Marks
the simplest BEAM circuits.
The Pock-Marks contain all the elements of an SE, the power
source (solar cell), the storage unit (capacitor) and the
However, what makes it a Proto-BEAM circuit is that it
does not have a latch mechanism.
is perhaps the simplest and most primitive
in the evolutionary sense of the BEAM SEs. It
requires an external trigger (divine intervention)
to run the motor.
Specifically this design has a problem that the
accumulating cap. voltage might ruin the solar
design has a diode in series with the negative
rail avoiding possible damage to the solar
design also incorporates a transistor
The latch introduced in this design is
like the one used in the FRED
SCR Based SEs This
SE may, in fact, be a version of the common evolutionary
ancestor of many the other SEs, specifically these using
an one PNP and one NPN transistor. This is due to the nature
of the SCR.
References: The SCR solar engine was designed by John Iovine
of Images SI Inc.
The circuit was first published in Nuts & Volts Magazine,
Diode Based SEs
The Simple FLED SE
In low light, it's a Type
1 SE (Voltage controlled), and in bright light,
it's a Type
2 SE (Time controlled). The reason is, there
is no transistor
latch for the SE. It's only on when the FLED is
on. Another cool feature is, when in bright light,
there is a maximum ON time.
The Zener-based SE
The two diode SE
The LED Logic SE
1381 Based SEs
Standard 1381 SE
1381 Based SE with
The Miller 1381 SE
The Miller 13812 SE
as above but uses the 13812 and a PNP
[Move mouse over the circuit
to see the differences from the Miller