Solar Robotic Dual 55 Gallon Drum Composter (Vex Lancer Bots Project)

Helping the environment one robot at a time!!

Thursday, I turned over our working dual 55 gal drum solar robotic composter to Bettina , a volunteer gardener in the Grant High School Serenity Garden.

IMG_0821The garden has been in the news over the years but has  run down considerably.   Thanks to volunteer Master Gardeners and the Tree people, it is undergoing a transformation back to its former glory.

The kids on the Grant Vex team 1508 (Lancer Bots) coached by Mujtaba Khan  worked hard this spring to complete the project before school was out.  The project was funded by a $1000 IEEE grant obtained through ARC foundation but we only spent about 60%.  ARC Grant representative Wendy Castellanos has been our biggest supporter and we owe her a big Hug.    The project was conceived by Roots and Shoots school environmental club and  led by Beth Davis, a member of both clubs. Shown below are Beth and I with the first photo of the near finished product.   Beth is on her way to UC Santa Cruz in the Fall.  I will miss her great spirit.The Vex team was given the job of design and construction.   They didn’t quite finish before the end of the school year,  so Beth  and Ramin Khajeh  spent a few days this summer with me completing the adjustments to handle the weight of the compost that was dimpling the 55 gal drums and install the solar panel.  The main difference from this photo is that the support and drive wheels were moved outward toward the rim to give more structural support.

The composter has a programmable timer that switches relays on to drive the motor for 2 minutes per day which in turn rotates the barrels about 5 rotations.      Rotating the barrels aerates them and the composting time is considerably shortened (about a month).   The barrels are held on a 2×4 treated lumber frame.

Drive Train:

The drive train consists of a 1/2 inch stainless steel axle with two 4 in drive wheels.  The axle is driven with a cog belt pulley system that provides a 4.5:1  gearing to a Taigene van door motor (I borrowed/stole this from  my 599 team FRC kit).  It is held in place by four plastic self_aligning  flange  bearings donated by Igis.


The electronics/motor are powered by a 5 AmpHr battery that is recharged by a 8 watt solar panel through a charge regulator.   The solar panel is from an old highway call box.   It has a Ioc = .5 amps and a Voc of 21 v.

The motor draws about 8 amps while rotating.   It is designed to operate at 10 amps.  The electronics are housed in a water proof box.  A special thanks to Ramin for extra effort put forth over the summer.   He is on his way to UC Berkeley (my alma mater) after graduating as class valedictorian.  He too leaves a big void for the team to fill.


(Click on figure to englarge)

I will post my mentor design notes sometime in the future if the team decides they don’t want to sell the plans to raise money.    I did most of the detailed design to help them along where the mechanical/electrical became a bit too complex.  I tried to keep them on a systems engineering process best I could.   At some point we will get a good web site going on it but the kids got out of school before they wrote the report!!%$#

Sad to say, the only Vex parts used were a few nuts , bolts and aluminum beams.

3/27/2013  Posted mentor design notes here:   This is an excel program that contains detailed mechanical/electrical requirements analysis plus dimensions and materials used.   Also included is a tab on electronic circuitry.  Please ask permission to use designs.

DIY Dual Solar Robotic Composter video link:

Photos of the team during construction here: These give you a better look at the in- progress assembly.

I think this is a first!

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7 Responses to Solar Robotic Dual 55 Gallon Drum Composter (Vex Lancer Bots Project)

  1. Spencer says:

    Hello. My name is Spencer Jackson, and I am a junior at Manteca High School. Our school recently got a new program, called Environmental Science. My project is to build a solar-powered composter. Is it possible that you have plans, for I saw your video, and I absolutely loved the idea. If you do, may I use them?
    Spencer Jackson

  2. says:

    Requesting permission to use the design for a backyard garden.

  3. Hi I’m working with my local Habitat for Humanity to go Zero Waste. We would like to set-up a composting system. Would you be willing to share your design plans with us? I might be able to donate some money for them. Thank you ~amber

  4. Tom says:


    Did you know that your referenced URL for more information on this composter build is dead? Wayback doesn’t even have a saved copy. 😦 Simply says it was deleted and no forwarding URL,

  5. Dear Chris, I just sent you a request to purchase the detailed plans so we can use this design on our family farm. The message was sent to your account. We might even like to purchase the electronic box and control panel fully built if your students are willing to put it together for us. We will compensate them to do this. It shortens our cycle time in assembly.
    Thanks so much. This is the most resourceful, brilliant design I’ve ever seen. Professor Dawn M. Fotopulos, The King’s College, NYC

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