Digital Step Km Counter Circuit

This circuit is designed for 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. The rightmost display D1 (the least significant digit) shows hundred meters and its dot illuminates after every 50 meters of walking. A beeper (excludable), signals each count unit, occurring every two steps. This is the figure of the circuit;

This circuit has operation with based on 2 IC. IC1A & 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 divides by 64. Q2 drives the LED dot-segment of D1 every 32 pulses counted by IC2. Either IC3 & IC4 divide by 10 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 allows to disabled the beep.

A normal step was calculated to span around 78 centimeters, thus the LED signaling 50 meters illuminates after 64 steps (or 32 operations of the mercury switch), the display indicates 100 meters after 128 steps and so on. For low battery consumption the display illuminates only on request, pushing on P2. Accidental reset of the counters is avoided because to reset the circuit both pushbuttons must be operated together.

Part:

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)