Parts of Component:
R1, R3 22K 1/4W Resistor
R2 2M2 1/4W Resistor
R4 1M 1/4W Resistor
R5, R7, R8 4K7 1/4W Resistor
R6 47R 1/4W Resistor
R9 1K 1/4W Resistor
C1 47nF 63V Polyester Capacitor
C2 100nF 63V Polyester Capacitor
C3 10nF 63V Polyester Capacitor
C4 10µF 25V Electrolytic Capacitor
D1 Common-cathode 7-segment LED mini-display (Hundreds meters)
D2 Common-cathode 7-segment LED mini-display (Kilometers)
IC1 4093 Quad 2 input Schmitt NAND Gate IC
IC2 4024 7 stage ripple counter IC
IC3, IC4 4026 Decade counter with decoded 7-segment display outputs IC
Q1, Q2 BC327 45V 800mA PNP Transistors
P1 SPST Pushbutton (Reset)
P2 SPST Pushbutton (Display)
SW1 PST Mercury Switch, called also Tilt Switch
SW2 SPST Slider Switch (Sound on-off)
SW3 SPST Slider Switch (Power on-off)
BZ Piezo sounder
B1 3V Battery (2 AA 1.5V Cells in series)
Description:
This schematic measure the distance covered during a walk. Hardware is located in a small box slipped in pants pocket and the display is conceived in the following manner: the leftmost display D2 (the most significant digit) shows 0 to 9 Km. and its dot is always on to separate Km. from hm. The rightmost display D1 (the least significant digit) shows hundreds meters and its dot lights after every 50 meters of walking. A beeper (excludable), signals each count unit, which occurs every two steps. A normal step is calculated to span approx. 78 centimeters, thus the LED signaling 50 meters lights after 64 steps or 32 mercury switchs operations, the display indicates 100 meters after 128 steps and so on. For low battery consumption the display lights only on request, pushing P2. Accidental reset of the counters is avoided because to reset the circuit both pushbuttons must be operated together. Obviously this is not a precision meter, but its approximations degree was found good for this kind of device. In any case, the most critical thing to do is placement and sloping degree of the mercury switch inside the box.
The principle operation:
C1A & IC1B form a mono stable multi vibrator providing some degree of freedom from excessive bouncing of the mercury switch. Therefore a clean square pulse enters IC2 that divide by 64. Q2 lights the dot of D1 every 32 pulses counted by IC2. IC3 & IC4 divide by 10 each and drive the displays. P1 resets the counters and P2 enables the displays. IC1C generates an audio frequency square wave that is enabled for a short time at each mono stable count. Q1 drives the piezo sounder and SW2 let you disable the beep.
