Proof of Concept. Pneumatic Timer for Tracking Solar Panels and for Moving Greenhouse Curtains.

I think this is a new kind of "timing circuit" or "clock drive" that uses varying air pressure to transmit timing information to the devices that it controls. In theory, equatorial mount is the simplest way to track the sun for solar panels, it a system that works by slowly ROTATING the solar panel on a single axis at the right speed 15 degrees per hour, you can manually adjust things weekly or bi-weekly for perfect tracking as the suns path rises in Summer and lowers in Winter. (instead of the much more complicated to control rotate and tilt for more common mounts (altazimuth mount). I put a solar panel on equatorial mount but I couldn't find a really slow motor to turn it at EXACTLY the right speed. Even if I had found the motor at the right speed, I would have to make all the wheels, and gears exactly the right size to make things turn accurately This is fine engineering, and requires excellent design and high quality components from day one. I needed a design that you could do quickly and then correct the errors. Plus I want to turn several solar panels in different locations, so it could get pricy. I had to find a different way. Instead I used a slow synchronous motor combined with a gearbox from a desktop fan, to slowly raise a float, to use slowly increasing air pressure to move the solar panel. It worked! But it was a bit too fast! The final part of the jig saw was a programable on off timer. with it, and using a bit of math, I could slow down the pressure increase so that it moved the solar panel at exactly the right speed. This is just the proof of concept where I used the cheapest materials available to me, so there were many compromises but it is surprisingly accurate.

Supplies

Bench drill, jigsaw, 1 by 4 wood, solar panel, 2 fifty gallon barrels, an old garbage can, garden hose, clear plastic tubing of various sizes, rubber tubing, 4 inch drainage pipes and caps. 5/8 inch bearings 5/8 inch bar 3ft long. old bicycle tube, heat gun or butane flame. Fishing line.

Step 1: Cut a 4 Inch Pipe in 4 Equal Sections, Then Silione End Caps On

In this demonstration, I will only use 2 of the 4 cuts, the 4 inch pipes come in 10 ft lengths so each section is 2.5 ft long. one section has 2 end caps and a hole in the top end cap so that the low pressure air is allowed in through a 1/4 inch tube, while the other one has just one end cap. Both are connected at the bottom by a 1/4 inch tube so that water can be pushed by the low pressure air from one side to the other.

Step 2: Float Valve Design

This step took a while because I had to get the right soft rubber tubing for the valve. There were several to try. and I had to get the right weights and distances for the "lever bar" by trial and error. Essentially it works because when the water is lower than the float in the pipe, the float pulls on the fishing line and on the "lever bar", and lift the lever bar off the rubber tubing. This lets air from the air pump through and it keeps coming through until the water rises in the pipe and pushes the float up. This releases the pull on the lever bar and it clamps down on the rubber tube and cuts off the air.

Step 3: Power Train for the Slow Motor

I bought a slow motor from amazon. Unfortunately, I did not realize that some (most!) of these motors can go any direction when you start them. Completely depending on the mood of the motor, it can start going anticlockwise or clockwise. Because I was brought up in Ireland, where we say anticlockwise, I did not realize that CW and CCW meant clockwise and counter clockwise. When a synchronous motor has CW CCW on it, it means it is useless for my experiment. So, first thing I did was I bought the wrong slow motor and I was completely puzzled when it gave awful results especially when I used the timer to start and stop it. . Eventually I bought its replacement, a CCW motor that reliably started going counter clockwise all the time. This motor was still much too fast, so I had to gear it down. I spent a few days taking apart various appliances with gearboxes in them and eventually found an old office fan in a thrift store. I took it apart and found that it worked smoothly and the gearbox (that runs from the fan motor and changes the direction that the fan blows) was close to what I needed. Still too fast but reliable! So, I have the slow motor and a coupling ( a piece from a ROC drill set that helps you do the right depth, then the housing for the fan, and a top of plastic bottle is the "gear wheel". Fishing line winds up on the gear wheel as the motor turns and lifts up the float really slowly.

Step 4: Last Piece of the Jigsaw!

As I said, the slow motor raised the air pressure too fast and consequently it rotated the solar panel too quickly. I consulted with my brother who is an electrician, and he suggested this programable on off timer.

Step 5: Calibration

The first thing to do was to check that air pressure was increasing at an even speed all day. So I spent a day measuring it. At the same time I checked how quickly the equatorial mount was rotating. Then I did some math and set up the programable timer to turn on and off every couple of minutes for the right duration.

Step 6: Prototyping the Equatorial Mount Drive

My original equatorial mount set up was not great because I couldn't find identical small cylindrical plastic cans cheap enough to make the whole thing from them. So I made something that was "half right" (but worked reasonable well). I have to refill one of the containers every evening so it is ready to work again in the morning. Eventually, I made the decision to "over build" a new prototype, that was way more powerful than what I needed but which cost the same and worked better. Unfortunately, the sun pretty much disappears in the clouds here in mid October, and returns in late February, early March, so I have not been able to give it a good fully loaded trial yet. This one is totally automatic, and completely pressure dependent.

Step 7: Enhancements, Manometers, Etc

I'm not going to go into great detail on this one, I added some things so I could better take measurements of air pressure, and how well the device tracked the sun, etc.

Step 8: A Future of This Idea?

This is essentially an air pressure based timing circuit. It could be used to open a valve to let air into a container to pull closes night curtains in a greenhouse in the evening and open them in the morning simply by pushing water from one container to another. I have two 4 inch pipes left over with which I can do that. Another thing is I could have a "cam" attached to the rising float, and the cam can work like the old punch tape computers to switch air circuits on and off as it rotates. This could switch on and off my "tip and drip" watering system, which currently is on too much because I use the low pressure air to oxygenate a fish tank too. Another thing, is this idea (low pressure air controlling movement) could be used to work more standard solar mounts. (Where the solar panel rotates on a horizontal axis and tilts up and down). In this case, you would need 2 air circuits, and either have their air pressure controlled by an equatorial mount in an analogue fashion or by a mini computer. I had to start somewhere with the idea, so everything I did was chunky and clunky, but the whole timing part might possibly be one little electronic valve that gradually raises the pressure it allows through. In the next month or so, when the clouds go away in this area, I hope to work on it some more, test out different uses for the thing, and miniaturize it.

Step 9:

Step 10: Open Source Development?

Any suggestions as to how this can be standardized and have other people develop it too? A facebook group, or something like github. Some type of development center where people add improvements to the idea. If anyone wants to see how it has developed so far, you can find a playlist about it on my youtube channel. https://www.youtube.com/playlist?list=PLkzXlmAwZTZdwFHYgD8mp4RFg2-Ap-ZNy

Thank you for reading

Brian White