For this assignment I took apart the black and decker PlantSMART sensor for growing plants.  I thought it would be helpful because it includes a variety of sensors that could be useful toward the Bijoux modular jewelry kit that I plan to incorporate sensors into.

Parts list

Circuit: most of these parts can be purchased through digikey or similar parts supplier except where otherwise noted.

  • 1 microchip PIC18F4550
  • 20 capacitors, different packages sizes all SMD, both ceramic and tantalum
  • 24 resistors, different package sizes all SMD.
  • 1 16 mHz crystal oscillator
  • 2 Inductors
  • 1 pushbutton switch
  • 1 piezo speaker
  • 1 male and 1 female usb adapter
  • 1 battery holder and AAA battery
  • 2 voltage regulators
  • 4 diodes (including LED’s)
  • 1 temperature sensor (thermistor)
  • 1 light sensor (phototransistor)

(Probe PCB that is exposed to the elements has special coating, as well as the exposed sensors)

  • 1 fertilizer sensor (don’t know what it is – this is a non standard part)
  • 1 simple sensor for conductivity/moisture (this needs to be fabricated on a case by case basis)


  • Vinyl flower
  • 4 piece injection molded plastic enclosure, white and opaque
  • 1 injection molded plastic light housing, white and semi-opaque
  • Silicon rubber coating around enclosure to protect from water
  • Silicon rubber battery holder
  • 2 small screws

Assembly sequence:

  1. PCB milling, machine stuffing of the components.  A few of the components may be hand soldered
  2. Injection molding of enclosure.  Machined
  3. Placement of finished circuit PCB on half of enclosure.  Other half of enclosure placed onto board.  Insertion of two screws.  This assembly is by machine.  I am now calling this the circuit enclosure.
  4. The circuit enclosure is dipped entirely in silicon/rubber coating. Machine or manual.
  5. Addition of vinyl flower and light cap.  This is either by machine or manually.
  6. Probe PCB is inserted into base of circuit enclosure and glued/sealed in.  This is done manually.
  7. Insertion of battery into unit.  This is done manually.

Cost of device is $17.99, so it was likely around $4 or $5 dollars to make.  EasyBloom was an earlier version of this device (essentially the same thing) that originally sold for $64.99.  This shows the difference in cost at different quantities.


One thought on “PlantSMART

  1. Jeniffer,

    How did you figure out that the assembly in #3 and #5 is done by machine? This seems to be a step that can be easily done and screwed manually, especially if the product is assembled in a place where manual labor is cheap.

    Did you find any information on how the silicon/rubber coating is casted (through dipping)? What process did they figure out to mask-out the parts that should not be covered during dipping? Did they use jigs to hold the parts during dipping? Would be interesting to see how complicated/easy this part of the process is.

    Based on this analysis, how much time would you guesstimate that assembly process may take?

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