Introduction: Solar Powered Composter

We are Robot Revolution, a First Lego League Team (, and this is our research project for the 2015 Trash Trek season. Composters don't process the leaves and kitchen waste very fast without some physical help from people. We all have a compost bin we add to and fill up but never seem to get much dirt out of it before it is filled, because nobody wants to go out and turn the yucky stuff every week. We are even too lazy to turn the drum ones! So we've invented a compost turner that uses solar power and a timer, so we never have to do anything other than dump in the new compost. We chose to retrofit the world's most used composted, The Earth Machine (tm), because there are over 2,500,000 people who use it in North America. You can buy a discounted one at most local municipalities.

Our invention has a screen at the bottom to let the dirt fall through to be collected and let more air in but the bugs can still get to the compost. Its more efficient and easier to collect the dirt. The turner moves everything so air can get to the compost.

Step 1: Gather Materials

Gather materials

1) 13 Watt Briefcase Solar Charger

2) The Earth Machine(tm)

3) ZYT16G microcomputer timer switch

4) ExpertPower 12 volt battery EXP1270

5) AndyMark PG188 Gear Motor, Encode Ready (am-2193a)

6) 16 standard screws

7) 1 bolt

8) A piece of 1.5x2.4(feet) cut log

9) 2 pieces of 2x4 wood cut 2 ft. long

10) Expanded metal 3/4 “x24”x24”

11) Zip-ties(4)

12) PVC pipe (cut it into 9.25 inches, 15.5 inches, and 1.5 inches)

13) PVC pipe T connectors

14) PVC pipe cap

15) 12 gauge wire with alligator clips

16) PVC glue

17) 10 millimeter key hub am-0985a

18) RioRand LCD DIgital Volt, Voltage panel Meter Voltmeter, 7.5V-20V

19) aluminum plate, 5 ½ inches long, ⅛ inches thick, and 2 inches wide

Step 2: Build Metal Screen

Flatten all metal corners (of the expanded metal) to a 45 degree angle, 7 inches in. Put the Flattened metal screen into the bottom of the composter.

Step 3: Make Wooden Support

Cut the 2x4 to 2 feet long, and then put the piece of wood into the top part of the composter. Drill a hole through the middle of the 2x4 piece of wood (make the hole in the wood 2.25 inches in diameter) so the motor can fit through it.

Step 4: Secure Your Wood Support

From the outside, screw four screws into the composter when the woods is put across; so the screws go through the composter and into the wood. Measure the composter yourselves and how high you want to put it up, ours was 26” from the bottom.

Step 5: Make Aluminum Plate to Attach Motor

Cut aluminium sheet to 5 ½ inch long, ⅛ thick, and 2 inches wide.We are going to attach the motor to the aluminium sheet to attach that to the wood. Refer to the picture of measurements, to drill the holes. Screw the sheet to the motor in two places. Then down to the wood.

Step 6: Attaching Battery and Timer

Strap the timer and the battery to either side of the motor (2 zip ties each).

Step 7: Make the Paddle Turner

We’ll make the turner next. Cut the PVC pipe to 9 inches, 4 inches, 8 ½ inches,3 inches, and 2 inches. Adjust the different pipes in the picture as shown. Screw the hub cap into the PVC cap, as shown above. Screw a screw into a PVC cap, so it holds onto the metal screen to keep the turner upright. Attach 2 PVC T connectors as shown above. Attach all of these features with PVC glue.

Step 8: Attach the Turner to Motor

Attach the PVC pipes to the motor, with the hub cap set screw. (don’t do this step with PVC glue).

Step 9: Wiring the System

Attach the alligator clips to the motor and battery, as seen in the picture.

Step 10: Test and Set Your Timer

Test if your battery is charged, then set your timer, for once a day.

Step 11: Making a Support for Solar Cells

If you want to solar charge your composter, you have to decide where and how to mount it. We mounted ours on a tree as seen in the pictures, with a 2x4 and plywood sheet.

Step 12: Secure the Solar Panel

Attach the Solar charger to the sheet of plywood.

Step 13: Connect the Solar Charger

Connect the wire from the solar panel to the batteries with the included alligator clips. If you want to monitor the voltage, you can use a RioRand digital voltmeter( #18 on the list).

Step 14: Pat Yourself on the Back

Give yourself a pat on the back, you’re done!

Thank you for looking at our instructions!

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