Introduction: IOT123 - SOLAR TRACKER - TILT/PAN, PANEL FRAME, LDR MOUNTS RIG

By bend. break, blend
About: The tension between novelty and familiarity...

Most of the DIY designs for dual axis solar trackers "out there" are based on the 9G Micro Servo which really are under-rated to push around a couple of Solar Cells, the micro-controller, the battery and the housing. You can design around having the battery and micro-controller separate, but this way you have the option of the Solar Tracker, battery, micro-controller(s) and the sensors/actors being incorporated into a single assembly.

This Assembly is specifically built for the MG995/MG996R servos and 2 off 69mm x 110mm solar cells. The Panel Frame is modular and can be adapted for other size cells.

A separate instructable/thing will be available for the battery/micro-controller, though this assembly is seen as independent and will fit in with your own solution.

These servos draw more current than the 9G; a sleep and day/night schedule should be employed with your tracking solution.

Features

  • Modular design - easy to customize for different size cells.
  • Sun proximity sensor array (LDRs) built in to panel frame
  • Strong servo movement
  • Hidden base fixture holes - fasten from underside.
  • Zip-tie friendly circuit cavity for battery/electronics

Expected Variations

  • Size and number of solar cells
  • Type and number of batteries
  • The size of the circuit cavity
  • The geometry of the tilt/pan reach

HISTORY

  • Dec. 15, 2017
    • Initial Submit
  • Jan 29, 2018
    • Height adjustment

Step 1: Materials and Tools

    There is now a full Bill of Materials and Sources list.

    1. 3D printed parts (see next step)
    2. 2 off 69mm x 110mm solar cells
    3. 4 off LDRs (Light-Dependent Resistors)
    4. 2 off MG995/MG996R servos
    5. 3 off DuPont Cable Ribbon Jumper Wire Female to Female 40cm (cut in half)
    6. ~20 off 4G x 6mm stainless self-tapping pan head screws
    7. ~10 off 4G x 9mm stainless self-tapping pan head screws
    8. Cable ties ~2mm wide
    9. Hot glue and hot glue gun
    10. Silicone sealant
    11. 2 off pairs of waterproof JST connectors
    12. Solder and iron

    13. Solder Flux

    Step 2: The Parts to Print

    The names of the parts relate to the STL filenames on Thingiverse.

    1. 2 off SOLAR PANEL side 138mm
    2. 2 off SOLAR PANEL side 110mm
    3. 4 off SOLAR PANEL corner
    4. 1 off SOLAR PANEL stay 110mm
    5. 1 off SOLAR PANEL bottom cover 138x110mm
    6. 1 off MG995 TILT PAN base block
    7. 1 off MG995 TILT PAN base lid
    8. 1 off MG995 TILT PAN corner
    9. 1 off MG995 TILT PAN vert arm
    10. 1 off MG995 TILT PAN vert bracket

    Step 3: Assembling the Panel Housing

    1. Affix 2 off SOLAR PANEL corner to SOLAR PANEL side 138mm with 4G x 6mm screws.
    2. Repeat point #1.
    3. Affix SOLAR PANEL side 110mm between the assembled pieces in point #1 & point #2 with 4G x 6mm screws.
    4. Repeat point #3.
    5. Affix SOLAR PANEL stay 110mm between the 2 off SOLAR PANEL side 138mm on the top surface with 4G x 6mm screws.

    6. Affix SOLAR PANEL bottom cover 138x110mm between the 2 off SOLAR PANEL side 138mm on the bottom surface with 4G x 6mm screws.

    Step 4: Adding the LDRs and Solar Cells

    1. Thread the leads from an LDR into the two small holes in a SOLAR PANEL corner from the outside.
    2. Bend the LDR so it is pointing upwards and prefit it so that is sits on the small ledge.
    3. Pull the LDR out and up slightly, put a dob of hot glue making sure it seals the holes.
    4. Push the LDR into its final position while the glue cools.
    5. Repeat points #1 to #4 for the other corners.
    6. On the inside of a corner, trim all but 7mm of LDR leads sticking out and tin.
    7. Solder a 20cm female dupont lead (1/2 a 40cm female to female lead) to the LDR leads.
    8. Add a dob of hot glue as insulation and strain relief.
    9. Repeat points #6 to #8 for the other corners.
    10. Pre-fit 2 off Solar Cells to top of panel frame.
    11. Turn over onto firm flat surface, ensuring panels stay in top groove.
    12. Apply bead of Silicone sealant to edge of cells exposed bonding to 3D printed parts.
    13. Clear the edges of the centre stay of silicone, where the MG995 TILT PAN vert bracket will be affixed later.
    14. Allow to dry.
    15. Apply flux agent to the output pads on the solar cells,
    16. Tin the output pads
    17. Solder female JST connectors to pads on Solar Cells.
    18. Route and affix cables to SOLAR PANEL bottom cover 138x110mm with cable ties.

    Step 5: Assembling the Lower Servo Base

    1. Insert Rubber Grommets into Servo mount holes.
    2. Insert Brass Bushes into Rubber Grommets from underside (flanges pointing down).
    3. Insert supplied screws into Brass Bushes from underside and affix to MG995 TILT PAN base lid.
    4. Affix MG995 TILT PAN base lid with mounted servo onto MG995 TILT PAN base block from underside with 4 off 4G x 6mm screws.
    5. Affix Round Horn to Servo with Machine Screw.

    6. Centre swing of Servo with short axis of SOLAR PANEL corner and affix to Round Horn with supplied screws.

    Step 6: Assembling the Upper Servo Arm

    1. Insert Rubber Grommets into Servo mount holes.
    2. Insert Brass Bushes into Rubber Grommets from underside (flanges pointing away from axle).
    3. Insert 4G x 9mm screws into Brass Bushes from underside and affix to MG995 TILT PAN vert arm.
    4. Affix Round Horn to Servo with Machine Screw.
    5. Affix MG995 TILT PAN vert bracket to MG995 TILT PAN vert arm with 2 off 4G x 9mm screws

    Step 7: Attaching the 3 Assemblies

    1. Centre swing of Upper Servo with long axis of SOLAR PANEL corner and affix to Round Horn with supplied screws.
    2. With end-cutters or hacksaw remove 1mm - 1.5mm from 2 off 4G x 6mm screws (will hit panels otherwise)
    3. Tilt the Upper Servo in one direction so as to expose a screw hole on the MG995 TILT PAN vert bracket
    4. Align and affix MG995 TILT PAN vert bracket to hole in SOLAR PANEL stay 110mm 4G x 6mm screw
    5. Repeat point #3 & #4 but in the other direction.

    Step 8: Height Adjustment and External Power Switch

    A height adjustment collar with facility for a power switch has been added and is an optional step. Say there are room constraints where you install your rig (such as a dome) and you want to drop the panels; this collar helps. Although we are showing the Rig being installed in our dome, the practice can be applied to other situations.

    1. Position the rig with the correct X/Y clearance
    2. Mark the base surface, with the outline of the box
    3. Cut the base surface on the outline, with a cut for the servo wires to pass through
    4. Place the bottom collar on the underside of the base surface
    5. Pilot holes using the six holes on the bottom collar
    6. Fix bottom collar to base surface with 4G x 6mm pan head screws
    7. On top surface place top collar on screws sticking through
    8. Tighten screws so that top and bottom collars tighten around base surface
    9. To add a switch
      1. drill the three holes out in the base surface where the wires will pass through
      2. pass a pair of wires through 2 adjacent holes
      3. Solder a PCB SPDT 2.54mm pitch 3 wire switch onto the wires
      4. Glue the bottom and side of switch in position with the bottom collar with Cyanoacrylate glue (clamping till set)
    10. Place rig base into collar, positioning to desired height
    11. Through the holes in the walls of the bottom collar drill pilot holes into the lower box of the rig
    12. Fasten 4G x 6mm pan head screws into the holes firmly
    13. Verify new height

    Step 9: Next Steps

    • Try this 18650 battery charger.
    • House the unit in this dome.
    • Try out this controller.
    • The Panel Frame can be detached at any stage, by disconnecting unsoldered cables ends, and reversing the previous step points #3, #4, #5.