Experimental Solar Cell Tracking Project for under $10
Recently purchase a couple of the small Solar Cell Modules on eBay (80x104mm 5V 250mA) and they work fine but it's time to add some tracking...

The 3D printed parts are simple enough so I thought I'd share...
I haven't written the code yet but will probably use one of the Arduino modules as I have lots (code has been added)...

Just to note I don't use LDR's to track the sun, I simply measure the solar cell's voltage and move it left/right, up/down a few degrees and determine the best position, no rocket science here, just simple measurements (will publish code when finished)...

Electronics Enclosure
Test enclosure allows for one or two PCBs and up to two 18650 batteries. The top is secured with four screws and cut-outs are included for the Solar Cell cable, horizontal servo cables and circular on/off button, the wall thickness is 3mm. I may add a more compact version later...

Parts Suppliers/Cost
Solar Cell banggood. €2.80
Charger Module eBay. €1.10
Micro Servo eBay. €2.26
Servo Test Unit eBay €1.50

The cost for the electronics should be around €6 (about $7) not including the Arduino Pro/Pro Mini which is a couple of bucks. Any microcontroller can be used and the code (to follow), can be ported as it's quite simple. All in, the cost should be close to or under $10...

Servos
As the servos I purchased are low cost I decided to test them using an inexpensive servo tester purchase on eBay (link above should you require one). The servos worked perfectly and can handle the weight of the printed parts and solar cell chosen. The actual rotation angle achieved appears to be a product of the tester's, I could only achieve ~100° on one and about ~120° on the other...

Modifying the Servos
It appears you can extend the rotation of any analogue servo by adding a couple of resistors to the feedback potentiometer but this was not necessary as when I tested with the Arduino and the servo example code, I achieve ~180° rotation.

While testing I noticed that on one end of the servos throw (when it reached a mechanical stop), it tried to go further. In time this would result in damage the cogs and/or motor, best set some limits to any functional code...

Code Update
Wrote a little code to manually test the design using a two servos, a couple of 10K pots, an Arduino Uno and the a few lines of code and it works a treat, now for some automation...

Sample Code Added actually works quite well...

Updates (may be edited daily)

• Removed original small enclosure as it was not adequate...
• Added a second Solar Cell Housing which includes a center support section to allow attaching of battery cable to restrict wear at solder joints. The cable can be attached to the support section using the included cable-tie hook (glue to the support)...
• Added some cable-tie clip prints to attach the battery and servo cables to prevent them from fraying or breaking from their solder points...
• Added some more code to update tracker every three minutes (tracker1.05.ino.txt) rename to tracker.ino to use with Arduino IDE. Change 'debug = false' to 'debug = true' to see console reports...
• Added Image of full sized version (using MG09R Servos), will add file after I print and test them...

21st April 2022, added Cell holder/bracket for cells measuring 110x69mm