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Step 3: Pull-Up Resistors

You will now be soldering four 3kΩ resistors to R1R2,  R19, and R20. These are pull-up resistors to hold the output of the comparator high.

This is because ICs are usually better at sinking current rather then sourcing.

Tools Needed

  • Soldering iron
  • Cutter

Parts Needed

  • 4 x 3kΩ resistors


  1. Find the resistor footprints on the board. R1, R2, R19, and R20 are grouped together next to the Propeller socket.

  2. Install the resistors into their footprints.

  3. Solder them into place.