V0.8 hardware integrates Rotary Encoders onto the back of each of the stepper motors. This is important to ensure that FarmBot always knows where it is in the circumstances when it has been inadvertently moved (by kids or pets) or it tries to move but is prevented from doing so due to some obstruction (rocks, branches, kids, pets). Unfortunately, there are no readily accessible add-on rotary encoders from popular sites like Adafruit or Sparkfun (as of September 2014), however, there are a handful of companies who do produce small, add-on encoders that mount nicely to the back panel of the stepper motor and hook onto a second shaft coming from the motor. The encoders modeled in the renderings below are based on those offered by Schneider Electric.

As of prototpying V0.8 hardware, low-cost rotary encoders have not yet been found or tested. Furthermore, the Arduino firmware does not yet support closed-loop feedback control.

Bill of Materials

Part Name Description Source $/unit Qty. Subtotal
Host Computer Raspberry Pi 2 Model B Adafruit $40.00 1 $40.00
Microcontroller and Stepper Drivers Arduino Mega 2560 R3, RAMPS shield, Pololu Stepper Drivers, USB cable Sainsmart $49.99 1 $49.99
Power Supply 12V, 30Amp Output OpenBuilds $35.00 1 $35.00
5V power adapter UBEC DC/DC Step-Down (Buck) Converter - 5V @ 3A output Adafruit $9.95 1 $9.95
Electronics Housing Waterproof McMaster Carr $32.34 1 $32.34
M5x10mm Screws M5 machine screws, 10mm length, 0.8 thread pitch, low-profile 3mm hex heads McMaster Carr $0.18 2 $0.36
Tee Nuts Stainless steel, for attaching M5 screws to OpenBuilds aluminum extrusions   $0.30 2 $0.60
        Total $169.64

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