1. Solar Cells
motor.jpg)
Testing different solar cells and making the Energy Converter Exercise to observe how many volts and current those solar
cells produced in order to make a motor run
2. Solar Miller from Solarbotics
Chris ordered this Solar Miller engine from Solabotics.com. It was a good starting point to understand how solar engines function.
A solar engine is build with a solar cell that receives radiant energy that it is stored by the capacitor and then utilizes that energy
to power a motor. This circuit uses a 1381 transistor that works as a voltage detector. It acts as a switch - when it detects that the capacitor is storing around 3V it opens and applies voltage to the base of the 3904 NPN transistor and this one applies current
to the motor. This process will continue until the voltage detector sees a voltage < 3V.
3. Building the beam circuit
Parts:
Solar Cell
0.47 uF capacitor
Diode
2N3904 Transistor
1381 IC Voltage Detector
Small Capacitor
Resistor ( not using - but it can be used btw the 2 transistors)
Building the Miller engine by yourselves, allowed us to test different components to the engine. For example, we tested with different capacitors: a 4700 uF capacitor that turn the engine on immediately and a 0.33F gold capacitor that took around 30 s to store the energy necessary to load the motor. With the first one, once we took the solar cell away from the light source, the motor stopped right away while with the other capacitor, even away fromt the light source, the motor continue to spins for 15 sec.
We also tested different 1381 transistor -- the voltage detector
The other small capacitor used in this circuit function as a timer. Larger values result in longer ( but less frequent) " bursts" of motor activity; smaller values result in shorts bursts but more frequent.
4. Light/Dark sensing
Parts:
1 Solar Cell + solar engine ( described before)
2 Photodiodes
(G14668)
2 150 pico-farad capacitors
1 74AC240N Hex Logic Inverter
see circuit here
After building the Miller circuit, our next Step was to build the circuit to detect light/dark, since our beams are powering a motor in order to search for a best position to gather light/sun. Chris found in an amazing book, a circuit and a very good explanation about how it works. We decided to try to test it and build it.
It uses two photodetectors, that will be placed at both sides of the solar cells, to detect a specific threshold ( controlled by the resistor in series with the solar cell). When both photodetectors receive the same amount of light, the motor is not loaded/ is stopped;
when one of the photodetectors receive less light, the motor moves in order to receive more light.
We had some problems when trying to combine this circuit with our solar Miller engine. First we tried just power it using arduino
( 3.3V) or a 9V battery just to check that it was everything ok with the circuit. Then we try with the solar engine from solarbotics and it was working, even if sometimes very unstable - sometimes working, other not working. With our solar engine (on the breadboard) we had some dificulties in putting both circuits working together - the motor wasn't receiving enought current to work. We tested also using different voltage detectors in the solar engine to see if with more voltage, it was possible to put the motor working. We also tested using different capacitors in the light/dark circuit to see how it changed and in the end the problem was related with current and not with voltage. We needed more current to run the motor!
The two circuits together( final circuit that we want to make) working bad
Final circuit working better - almost there.( noticed that also the light is not the same int the 2 photodetectors)
5. Generating Light
Another part of this project is to turn this sculpture into a night chandelier. This circuit is charging continously during the dayand dischanging when it's dark. In our circuit, AAA Baterries are being charged. We are using the SIMD1 V1 that requires almost complete darkness before switching. It uses a 74*14 Schmitt inverter to switch power on within the load.
Parts:
1 Solar Cell
1 Germanium Diode 1N34a
1 led
1 1M ohm resistor
1 3.3 ohm resistors
1 74HC14N Quad NAND gate
see circuit here
6.Perfboard
6. First Prototype
5. Final Project
Miller Solar Engine + Light Seeker + Nocturnal Engine
Parts used in each Bot:
(1) N914 Diode
(1) 1N34a Germanium Diode
(1) 1M ohm resistor
(2) 3.3 ohm resistors
(2) LEDs
(2) 150 pico-farad capacitors
(1) 10uf Capacitor
(1) 4700uf Capacitor
(1) 100 pico-farad capacitor
(1) 74AC240N Hex Logic Inverter
(1) 74HC14N Quad NAND gate
(1) 2N3904 Transistor
(1) 1381L Voltage Trigger
(14) Header Pins
(4) AAA Nicad Batteries
6. Printed Circuit Board
