Step 7: The Electronics...

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...
your sun tracking system is very simple and clever, i just imagine how much it will heat on desert areas, like mojave :D
brilliant work.<br>
Your design seems really simple and effective. The thermometer showed that it reached a good temperature. I will definitely try this maybe on a smaller scale and keeping an eye on cost. Thanks for the instructable.
Nicely done! I have been goofing around with this kind of tracker, wondering how to switch more current with it... didn't think to do it mechanically. I have used the method to construct a leave-me-alone box (about 5 or 10 in fact). Thanks for sharing!<br>jim in sweden
The method of tracking here is genius - it's incredibly simple but self regulating, great job...
How about plastic mirrors? It would reduce the weight. And would perspex/acrylic work instead of glass?
Are glass-faced optical mirrors really a good choice ?<br><br>I would have thought aluminized mylar would be more efficient reflectors as well as lighter and less prone to being ruined by water ingress.
Maybe... I did not go that far into it... I just wanted the maximum reflection I could get and these work really well... <br> <br>I got it out the garage earlier this week after winter... It worked first time, did not even have to charge the battery... Cooked a whole chicken in about six hours... <br> <br>Am looking at a smaller version using cool room panels....
It's a bit of a myth that because you can see your face in it, it must be an efficient reflector - the light has to pass through the glass twice. I made that mistake in a makeshift greenhouse when I first started gardening.<br><br>I'm inspired to have a go with aluminized mylar food packaging - it works very well as a reflector for my bike light. I'm told emergency blankets are a good cheap option - perhaps I'll hang around next time they hold a road race in my City. :)
How exactly do the mirrors benfit this? From the looks of it the angles don't add up to anything that would make it into the box.
The mirrors are set at that angle so that when they are facing directly at the sun its rays are deflected directly onto, and through the glass. Lets say the sun is hitting the glass at 30 degrees Celsius. It will be hitting the mirrors the same, but because of the deflection about 10% of heat is lost when reflected to the glass. So the mirrors are sending about 27 degrees Celsius. So you have 30+27+27 = 84 degrees Celsius hitting the glass. <br> <br>I am not sure where you get the box thing from. If you are referring to what some call box cookers I believe that refers more to the cooking chamber itself. It is a box shape usually with a closed top (as mine is) instead of an open type surrounded with reflectors where to cooking pot needs to be put in some sort of green house effect. Usually an oven cooking bag. That was my first solar cooker and they work very well. A little tip for anyone using these I found the cooking bags very awkward. So what I used was a plastic dome I got from a gardening shop what they use to protect new plants from the frost etc. <br> <br>If you are suggesting the mirrors would work more efficient at right angles to the glass, only a small percent would reflect directly onto the glass The rest may get to the glass after a zig-zag effect bouncing from one mirror to the other. Not very efficient as you loose about 10% of heat each bounce... <br> <br>I hope this has answered your question. It is only my way of seeing it and I stand to be corrected by anyone who knows a lot more about it than I do.... <br> <br>Thanks for your comment Steve... <br>
Great I'ble. <br><br>I like the recycling of the Baxter boxes. I get a butt load of them every 2 weeks.<br><br>I would like to see a use for all the tubing that comes with them. We use the 5000mL stuff.<br>
I used to get a monthly delivery of the boxes. Fortunately that has stopped now as I was lucky enough to get a transplant last November... I used some tubing to set up a automatic watering system for my seed trays... <br> <br>Thanks for all the positive support guys. Glad to hear it's encouraging others...

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