JCM inVentures Inc.
Building a Chloroplast Solar Engine
This great little solar engine is easy to build, and very powerful. If you would like a free printed circuit board ( the black part ) please email me at firstname.lastname@example.org and let me know where to mail them. I'll send you a few!
If you would like to get the entire kit, click here!
Here's how to solder the solar engine together!
CYBUG CHLOROPLAST Solar Engine
The Chloroplast in a living plant is the structure responsible for conversion of energy from the sun to food for the plant ( in the form of starches ) . Similarly, the CYBUG Chloroplast converts solar energy to electrical energy in a controlled and efficient manner for use in small robotic lifeforms such as the Solarfly. It is an excellent solar engine for larger robots, walkers, and solar powered robots with on-board microprocessors such as the BASIC STAMP.
I built the Chloroplast circuit because I enjoyed tinkering with BEAM circuits, but didn't appreciate how the conventional solar engines dropped ALL energy across the motors ( leaving none for logic or uP ) and the low voltage they operated at forcing me to use very low torque pager style motors. I wouldn't be happy until a CYBUG sized robot and motors moved quicker and with more oomph than my smaller BEAM robots. I really found the circuit that I need in this Chloroplast, and I'm pleased to share it with you here!
Theory of Operation:
The heart of the Chloroplast is the Motorola MC34164-3 Micro power Undervoltage Sensing Circuit ( U1 in the following diagram ). In normal use, this component monitors the voltage at pin 2, and applies a ground at pin 1 ( out ) when the monitored voltage drops below 3V ( 34164-3 monitors 3 volts, 34164-5 monitors 5 volts ). This low will then be used to assert a RESET on a microprocessor circuit. The output ( an open collector ) will be open when the output is above the threshold voltage.
Through tinkering, I have discovered that placing a 220K to 270K resistor in series with the input of U1 will produce a significant hysteresis in this sensors output. For instance, a 220K resistor as R2 will cause the output to ground until the solar voltage hits 6.8V, at that point it will open (float) until the solar voltage drops to 5.5V. ( A 1.3V hysteresis ). Different values of R2 will produce different results.
So how does this all work together? Well,
Free-form your own Chloroplast Solar Engine.
I picked up all my components from Active
Components (http://www.future-active.com/) with the exception of the
solar cells which you can get from us if you like. The MPSA12 Darlington and
34164-3 Voltage Sensor are Motorola
The following diagram illustrates how you can free-form your own Chloroplast solar engine. The 34164-3 and the MPSA12 parts are shown as a bottom view ( pins facing up, out of the screen ). The two 3-pin devices may be held together ( face to face ) using foam double sided tape. Using two solar cells is optional, but if you use 1 solar cell, be sure to use a lower value of R2 to accommodate the lower voltages.
I hope you try the Chloroplast Solar Engine, and tell me what you think! I've found it a great alternative to other BEAM style solar engines, and opens the doors to a greater evolutionary diversity in your robots.
Craig Maynard email@example.com
Updated July 11, 1999