I used a PIC16F819 microcontroller and a sensor from an old computer mouse (the remaining parts of one of my other projects Crazy Mouse) to make this simple measuring tape.
Do you want to make yourself? If yes read the rest of this instructable.
Step 1: What you need
- Printed circuits (find files in the next step)
- Copper board
- Circuit board acid
- 1mm drill
- Soldering tools
- 1x PIC16F819 microcontroller + socket
- An old mouse (or one of its IR shaft encoders)
- 3x BC547 transistors
- 3x common anode 7 segments
- 1x 100uF electrolyte capacitor
- 1x 470ohm resistor (1/8 watt)
- 7x 10k resistors (1/8 watt)
- 2x Simple push buttons
- 1x Simple switch
- 2x AA batteries with a battery holder
- 1x Wheel (+ maybe some gears)
- A box for this measuring tape
Step 2: Making the PCB
- Print the circuit on a glossy paper with a laser printer without scaling.
- Cut some copper board and clear it with sandpaper.
- Put the printed circuit on it.
- Press the hot iron on the board.
- Remove the papers.
- Soak boards in acid and wait till visible copper disappears.
- Wash the boards.
- Drill the holes.
- Clear the board with sandpaper.
Step 3: Soldering components
- Solder the mouse IR transmitter and receiver on the board.
- Solder 470ohm resistor behind the IR transmitter.
- Solder 10k resistors on the board.
- Solder some wires on the lines that connect two holes together. (jumpers)
- Solder microcontroller socket on the board in a correct direction.
- Solder seven segments.
- Solder transistors.
- Solder buttons with some wire.
- Solder the capacitor on the board in a correct direction.
- At last solder the switch to the battery holder and solder its wires to the BAT terminal.