Km Counter / meter circuit


Posted on Mar 17, 2013

This circuit measures 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 switch's operations, the display indicates 100 meters after 128 steps and so on. For low battery consumption the display lights only on request, pushing P2.


Km Counter / meter circuit
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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 approximation's 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. 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______SPST 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) IC1A & IC1B form a monostable multivibrator providing some degree of freedom from excessive bouncing of the...




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