Instructables

Step 7: The Electronics...

Picture of The Electronics...
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Now we come to what I believe is the most exciting part of the project. Even though most will agree it is a very simple system it took weeks to get it just right. I built several solar panels of differing sizes to find the one that would operate the electrics most economically. I tried several switches and switching devices until I found one that worked each and everytime without fail. There is probably still room for improvement, but this has performed better than my expectations...

I made up two small solar panels each producing about 3.3 volts in good sunlight. I joined them together with hinges.I then cross wired them to each other. That is I took the positive(red) from one and the negative(black) from the other and joined them. I did the same with the other two wires. I then got a servo and modified it by taking out most of the electronics leaving me with the DC motor and gearing. I connected the two motor wires to the two wires now coming from the solar panels....
I'll explain how it will work. The solar panels are set up so they face away from each other. That means where ever you place them one will be getting more sunlight than the other. Providing they are not pointing directly at the sun when both will be getting the same amount of sunlight. So the panel facing the sunlight will be producing more power (volts). That means that panel is controlling which way the servo will rotate because of the cross wirering. The servo reacts to the signal and either pushes or pulls the rod connected to a toggle switch. The toggle switch via a small 12 volt battery sends power to the motor which turns the oven towards the sun.
The switch is a DPDT (double pole double throw) with six connectors and three positions. On, off and on. It is wired up in such a way that the two on positions are reversed to each other. So when you connect a motor  it will turn clockwise or anti clockwise depending which way the switch is moved. The centre position is off....
So the oven is rotating towards the sun. When the oven reaches a position directly facing the sun both panels receive the same amount of power which causes the servo to centralize and move the switch to the off position stopping the motor. If the oven goes past the sun the servo will turn the other way making the motor reverse until the oven directly faces the sun.I installed an on off switch that kills the power from the 12 volt battery to the motor when the oven is not being used. Most other systems I have seen need a reset function to turn the oven back to the east for the next day. My system will automatically find the sun wherever it is in the sky. I mounted it all on a triangular piece of plywood that can be moved from side to side for fine adjustments.
I can see this system being utilized in other applications that need a simple and reliable way of tracking the sun...
 
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