Solar Linear Actuator

In order to improve the efficiency of the solar panel we need to keep the solar panel focused at the sun. To do that we need a North and South axis that will control the inclination of the panel. Instead of buying a solar linear actuator that could cost a couple hundred dollars I have decided to build one for less than fifty dollars. Here's how.

Let's start with the circuit for the solar linear actuator. I used a dual op amp 5532 although most any dual op amp should work. The two outputs from the op amp controls the H-Bridge for the North and South direction of the motor. The two CDS cells controls the inputs to the op amp. The CDS cells have a north and south orientation. The 100K pot adjusts the gain of the amplifier and the 10K pot adjust the sensitivity of the CDS cells. When the CDS cells see equal sunlight there is no output from the op amp. As the sun moves causing less light on the south cell the op amp will drive the H-Bridge causing the linear actuator to move the solar panel to the north until both CDS cells see equal sunlight.

You can buy all the components at JAMECO.com

Here is the circuit I built, I added a terminal strip to make it easier connecting the pots, cds cells, motor, and power. In this picture I was testing the circuit, works great.

Here is a diagram of the solar panel linear actuator. Here we have three pivot points just for the North and South axis. Later when we add the East and West axis we will add a fourth pivot point. I used 1/4 20 allthread for the actuator rod. This is a standard 1/4 inch allthread with 20 threads per inch. When selecting a motor for the linear actuator think about how fast a response you want from the actuator. A 20 rpm motor would drive the solar panel one inch in one minute. A 120 rpm motor would drive the panel six inches in one minute or one inch in ten seconds.

Here is a 150 RPM gear motor from JAMECO.com that will give you around seven inches of linear motion per minute, or a little over one inch in ten seconds. Jameco has different RPM gear motors, or you can Google gear motor for a more detailed list of gear motors.

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I'm using a 4 inch caster wheel with the wheel removed and a channel bracket to get two pivot points.

I mounted the caster and bracket in the center of the back of the solar panel.

Here is a picture of the linear actuator.

I used a 1/4 inch rod coupling I bought at Lowes for about 1 dollar for the stationary end of the actuator. I drilled and tapped the center of the coupling to 1/4 inch. The two 1/4 inch screws once fitted to a bracket will allow the this end to pivot.

Here again I used a 1/4 inch rod coupling to couple the motor to the all thread. I also drilled and tapped each end and used 1/4 inch set screws to secure the coupling to the all thread and the motor shaft.

This is a picture of the motor pivot bracket. It's made from a piece of sheet metal channel.

Here is the motor attached to the motor bracket, again I used a piece of scrap sheet metal.

It's a good idea to add end of travel limit switches to any type of linear actuator. The above diagram illustrates a very easy way to do this with a limit switch that only has one normally closed set of contacts and a diode. As you can see in this diagram that current can flow in either directions. The actuator can travel either North or South.

In this diagram we see the North limit switch has opened and no current can flow through the limit switch or the diode. Now the actuator can only travel to the South because current can flow through the North diode because of the change of pollarity in current flow.

Here we see the actuator traveled South until the South limit switch opened and stopped the motor. The actuator sets in the position until there is a need to travel North. The process starts over again.

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