MATERIALS Circuit board, about 3"× 4" RadioShack part #276-168,
radioshack.com DIP sockets: 8-pin ( 1), 14-pin ( 1), and 28-pin ( 1) such as Digi-Key parts #A24807-ND, A24808-ND, and 3M5480-ND,
digikey.com Voltage regulator IC, 8-pin Digi-Key #LT1121CN8- 3.3#PBF-ND Microcontroller, Microchip PIC18F2321 Digi-Key #PIC18F2321-I/SP-ND. When you order, request hat Digi-Key pre-program your PIC with the code at
makeprojects.com/v/29. If you have your own PIC pro- grammer, then you can do the programming yourself. Requires MPLAB and C18 compiler to build, or just program the hex file onto the device. Op-amp IC, quad, LM324N package Digi-Key #LM324NFS-ND Resistors: 110kΩ ( 2), 160kΩ ( 3), 16kΩ ( 2), 750kΩ ( 2), 10kΩ ( 1), 200Ω ( 4) You can use 240Ω resistors for the LEDs, but with 200Ω they’ll be brighter. Capacitors: 0.1μF( 1), 1μF ( 6) Five of the 1μF capacitors must be non-electrolytic, because electrolytic caps can’t be used for the high-pass filters. The 2 remaining caps, 1μF for the voltage regulator and 0.1μF to stabilize the voltage reference, can be electrolytic. LEDs, 5mm: red ( 1), green ( 1), yellow ( 1), clear ( 1) RadioShack parts #276-209, 276-304, 276-021, 276-014 Pressure sensor, 5V, 7mA, 6-pin Mouser Electronics part #841-MPX5050GP1,
mouser.com Wagan Micro Dynamo LED Flashlight Charger Amazon
Gregory Hayes (D,E), Damien Scogin (F)
weight and make it more robust. Since it’s
automated, readings are more precise and
not prone to human error. A reading takes
less than 30 seconds.
1. BUILD THE CIRCUIT BOARD
1a. Cut the board to size.
With a black marker, mark the circuit board as
shown, and cut it with a saw (Figures D and E).
1b. Add the voltage regulator.
Place the 8-pin DIP socket into the upper
part #B00198GFAG, to be disassembled for the hand
crank. A cheaper hand crank can be used; they’re about
$2 in bulk from
right of the circuit board and solder the
connections as shown in Figures A, B, and F.
Solder a 1μF capacitor between pin 1 and
ground. Solder a wire from pin 8, to be connected later to the loose wire from the switch.
Solder 2 wires to the circuit ground, for the
crank ground wire and a battery ground wire.
1c. Add the filters.
Solder the 14-pin DIP socket onto the board
as shown in Figures A–C and add wires for
power: pin 4 goes to 3.3V and pin 11 goes to
ground. If you use wire thicker than 22 gauge,
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