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
D
E
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
alibaba.com.
3. 3
Voltage Regulator
Battery
C1
1μf
1 OUT
2
3 GND
4
IN 8
7
6
SHDN 5
F
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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