Harlem Academy June 2015 Workshop at RPI: An Automated Watering System for Plants

Students in grades 7-8 joined RPI's triple helix Fellows for a workshop in which they extracted CD drives and power supplies from trashed computers to create an automated watering system for growing food at home. They learned about the dangers of e-waste in landfills, and the alternative of recycling e-waste for a makerspace. Other learning outcomes included the advantages of urban agriculture (health, solidarity with others, etc.), and the fun of electro-mechanical hacking.

Here are some materials if you want to replicate the workshop in your school or program:
The lesson plan:

PPT slides on food deserts and urban agriculture (Dan Lyles)

PPT slides on E-Waste (Ellen Foster)

Materials list:
  • A trashed computer tower (plunder an e-waste recycling bin) or other source of an old CD drive
  • A 12-16V power supply - also e-waste
  • Some wire
  • Two DPDT relays that have coil input 5V & <40mA
  • An Arduino & its USB cable to a laptop
  • A moisture sensor (though you could make your own)
  • Some clear plastic bottles from waste bin (1/2 gallon juice or soda bottles works well)
  • (optional) surgical tubing, aquarium tubing, or other. Another option is to flow water by tilting the plastic bottle. Use your creativity!
  • A plant

Our instructable:
The Arduino code:

The circuit diagram: note that the motor is in the CD drive, and the moisture sensor is in the soil. The first relay (triggered by output from Arduino pin 3) is used to switch motor power on/off; since we had no spst we just used one side of the dpdt. The second relay (triggered by output from Arduino pin 2) is used to change polarity of the motor. The CD drive motors were rated for 12v; the diagram shows 16v because we recycled power supplies from discarded laptops. Try to use multistrand wire for anything requiring significant length or flexing, because the kids tend to accidentally break solid core wire by bending it back and forth. Soldering was an enormously popular activity, so you are best off if you firmly anchor parts (eg with hot glue) and then have terminals the kids can solder the multistrand from for making the lengthy attachments.
watering circuit.PNGrelay circuit diagram.jpg



Students explain:
HA video.PNG
Student research reports on environmental hazards:

Freddie Grey and Lead Poisoning

Environment Justice and Agbogbloshie

Burning E-Waste and Human Health