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This is the final step in the robot plant build. We hope you’ve enjoyed the project! We also hope that you’re getting your entries ready to submit to the contest, which ends on December 22.

As a reminder, here are the prizes. The grand prize winner will receive:

  • $200 in the form of a pre-paid gift card
  • Make: Electronics
  • Energizer® Night Strike Swivel Light

The runner up will receive:

  • Make: Electronics
  • $25 Maker Shed gift certificate
  • Energizer® Night Strike Swivel Light

Finally, here are a few handy contest links:

  • Finished? Submit your build to be in the running for these fabulous prizes!
  • Getting stuck? Have a question? Head over to the Forums and let us know!
  • Need to catch up? Check out the project page for links to all of the content!

Now, lets put a wrap on that robot plant!

Step 0: Collect supplies

Parts list:

  • Plant brains, plant stalk and papercraft flower
  • 1′ square of artificial grass
  • 22 AWG fence wire
  • hot glue or other adhesive (double-sided tape, epoxy, etc)
  • LED (red or green)
  • 220 ohm resistor
  • hook up wire

Tools:

  • Soldering iron and solder
  • hobby knife
  • flush-cutter
  • needlenose pliers

Step 1. Re-size the circuit board

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First, cut off the ends of the circuit board so that it will fit in the plant pot. The easiest way to do this is to use the hobby knife to score a line in the circuit board, then use the pliers to snap it off along that line. Save one of the ends so that we can re-use part of it in the next step.

Step 2. Cut out the touch sensor board

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The next step is to build a little touch sensor board that will fit between the fake grass and cardboard plant base. Cut off a small piece with at least six strips of connectors on it (as shown above). This will serve as a base for a touch switch.

Step 3. Add wire leads for the resistive touch sensor

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Solder two wire loops to the board, connected in the fourth and sixth strips from the left. Use 8″ long pieces of wire, so that there is enough length for them to connect to the main circuit board. The loops themselves should be at least 1/4″ in height, so that they just stick out of the grass. The center loop will be connected to ground, and the outside loop will be used as a sensor.

Step 4. Add a status LED

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Our main circuit board already has a status LED, however we won’t be able to see it once it is buried in the plant pot. Add a new one to the touch sensor board, to give some feedback when the switch is touched. First, add the 220-ohm resistor between the first and fourth strips, to act as a current limiter for the LED. Next, place an LED between the first and second strips, with the positive side (longer lead) in the second strip. Finally, solder an 8″ length of wire to the second strip, to allow the microcontroller to switch on the LED.

Step 5. Connect it up to the main board

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The final electrical step is to attach the sensor board up to the main circuit board. Solder the ground wire up to the ground rail on the main circuit board, the sense wire to Pin 3 on the microcontroller, and the LED line to Pin 5 on the microcontroller.

Our example build will react to this touch sensor by opening. If you’re planning to add any extra sensors (such as light, temperature, humidity, etc), you might want to add them now while the plant is still apart.

Step 6. Cut out a circle of artificial grass, and add wire anchors

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Now that the basic circuit is finished (whew!), its time to start final assembly of the board. Cut out a circle of artificial grass the same size as the cardboard cover, with a similar hole for the tape measure to extend through.

The next step is to use the fence wire to make anchors in the grass, that the fishing line will connect to. When the plant stalk extends, these anchors will hold the fishing line in place, which will cause the flower petals to open up. The anchors should be placed about an inch from the edge of the pot, at 120-degree spacing directly across from the flower petals.

Here is what ours looked like after we put it together, for reference:

mil_step_6_wire_anchors_assembled.jpg

Step 7. Mount the touch sensor

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The next step is to mount the touch sensor board and secure the cardboard base to the artificial grass. Use the knife to put three small slits in the grass, and poke the two connectors and LED through the holes. Once the sensor board is in place, use hot glue to secure the cardboard to the artificial grass. This will provide some extra weight, so that the grass doesn’t lift up when the plant stalk rises. Fit the pieces back into the pot, but keep the electronics outside of the pot for now.

Step 8. Tune the servo motor

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Now, connect up the programmer to the circuit board, and adjust the timing of the servo motor so that it raises and lowers the correct amounts when you press the touch switch. The constants in the example program allowed our flower stalk to rise about 8.5″ inches, which seemed right for our plant. Experiment with yours to find a good height.

Note: You can pull the tape measure out of the plant base easily, but have to use the servo to retract it. We found it easiest to set the “down” stage to be longer than it needed to be, and then adjusted the “up” stage to perfect the height.

Step 9. Tie down the flower

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Now that the flower height is correct, the final step is to tie down the fishing line so that the flower petals open automatically. With the flower extended, you’ll want to loop each fishing line through its respective anchor, then tie it down using a clinch knot.

Note: If you have some clamps on hand, you can use them to test the action before tying.

Step 10. Test it!


At this time, the plant should be in full working order. Press the button to make to grow up and bloom, then press it again to reset it.

Step 11. Extend it!

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Our basic plant currently has a pretty simple on/off touch sensor, but has potential to do much more. The precision 1-second timer would make it easy for it to bloom at a specific time, and the extra I/O ports can be used to interface to other environmental monitors, such as the temperature sensor used in the data logger, a light sensor, or a humidity sensor. It could even be connected to a computer, to react to the virtual environment; the sky is the limit! What will you program yours to do?


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