Electrical Connections

Gather the Parts

For this Propeller ActivityBot construction step, you will need:

Assembled robot
(2) 20 k-ohm resistors (red-black-orange)
(5) 1.5 V AA batteries
Needle-nose pliers
Masking tape

Make sure to use (5) 1.5 V AA batteries!
The ActivityBot's High Speed Continuous Rotation Servos are rated for 6 to 8 VDC.  Its 5 cell holder is designed for five alkaline cells because 5 x 1.5 V = 7.5 V.  It's true that new and unused 1.5 V alkaline batteries can add up to 8.2 V, but exceeding by only 0.2 V will not harm the servos in any way. 
The output of an alternate supply should be measured and verified to fall in the correct supply range before used as a substitute to avoid potentially damaging the servos.  

Label the Cables

  • Put a masking tape label on the end of each encoder cable and servo cable, near the 3-pin socket.
  • Trace each cable back to its origin to see what it is connected to.
  • Label each cable Right or Left, Encoder or Servo. 

Prepare the Servo Ports

Each pair of 3-pin servo ports along the top of the Propeller Activity Board (original or WX version) has a jumper on power-select pins to its immediate left. 

  • Important! Make sure there is no USB cable or battery pack cable plugged into the board - moving jumpers with power connected could damage your board.
  • Move the shunt jumpers into the configuration shown below. (If your jumpers don't have a little tab on them, needle-nose pliers will help.)
    P12 & P13: VIN
    P14 & P15: 5V
    P16 & P17, 5V


Plug In the Cables

The encoder and servo cables have 3 wires, white-red-black. When you plug these cables into the servo headers, be sure to align white wires with the pin labels along the top of the board, and the black wires along the row labeled GND.

  • Plug the encoder cables and servo cables into the servo ports
    P12: Left Servo
    P13: Right Servo
    P14: Left Encoder
    P15: Right Encoder


Add the Resistors

  • Using the 20 k-ohm resistors, connect the P14 and P15 sockets to the left of the white breadboard to the 3.3 V power sockets just above the breadboard.



Double-check your Connections

The ActivityBot won't work if a connection is wrong.  Double-checking now is easier than troubleshooting later.

  • P12 & P13 servo port shunt jumper — Set to VIN.
  • P14 & P15: servo port shunt jumper — Set to 5V.
  • Left servo cable — P12 servo port.
  • Right servo cable — P13 servo port.
  • Left encoder cable — P14 servo port.
  • Right encoder cable — P15 servo port.
  • All servo and encoder cables — Each plug is over all 3 pins of its servo port, with white cable closest to edge of board.
  • Left encoder cable — other end is firmly plugged into encoder sensor.
  • Right encoder cable — other end is firmly plugged into encoder sensor.
  • P14 socket — connected to 3.3V header with 20 k-ohm resistor (red-black-orange).
  • P15 socket — connected to 3.3V header with 20 k-ohm resistor (red-black-orange).
  • Both 20 k-ohm resistors — if you trimmed them, make sure the leads are long enough to sit all the way down in the socket for a good electrical connection.


Insert the Batteries

  • Place five 1.5 V AA 1batteries into the battery pack. 
  • Plug the battery pack's barrel plug into the Propeller Activity Board's (original or WX version) barrel jack.


Congratulations, construction is complete! 

  • Keep following the links below to set up your software and start programming.