Digital step-kilometer counter

Circuit diagram:

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 (100m)
D2_______Common Cathode 7-Segment LED Mini Display (Kilometer)
IC1______4093 Quad-channel 2-input Schmitt NAND gate IC
IC2______4024 7-level ripple counter IC
IC3,IC4__4026 Decimal counter IC with decoding 7-segment display output
Q1,Q2___BC327 45V 800mA PNP transistor
P1_______Single-pole single-throw button (reset) P2
_______Single-pole
single-throw button (display) SW1______Single-pole single-throw mercury switch, also known as tilt switch SW2______Single-pole single
-throw slide switch (sound switch)
SW3______Single-pole single-throw slide switch (power switch)
BZ_______Piezoelectric sound generator
B1_______3V battery (2 AA 1.5V batteries in series)

Purpose of the equipment:

This circuit measures the distance covered during walking. The hardware is housed in a small box that fits in a trouser pocket. The displays are designed as follows: the leftmost display, D2 (highest bit), shows 0 to 9 kilometers, with its dot always lit to distinguish between kilometers and hundreds of meters. The rightmost display, D1 (lowest bit), shows hundreds of meters, with its dot lighting up after every 50 meters walked. A buzzer (optional) signals each counting unit, occurring every two steps.
A normal stride is calculated to be approximately 78 centimeters, so the LED indicating 50 meters lights up 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 displays only light up when requested by pressing P2. Accidental resets of the counter are avoided because resetting the circuit would require operating both buttons simultaneously.
Obviously, this is not a precision instrument, but its approximation is good enough for such a device. In any case, the most critical thing is to properly position the mercury switch inside the box and set its tilt angle.

Circuit operation:

IC1A and IC1B form a monostable multivibrator, providing a degree of freedom to avoid excessive jitter from the mercury switch. Therefore, a clean square wave pulse enters IC2, which performs a 64-fold frequency division. Q2 drives the LED segment of D1 every 32 pulses counted by IC2. IC3 and IC4 both perform a 10-fold frequency division and drive the display. P1 resets the counter, and P2 enables the display. IC1C generates a square wave at an audio frequency, which is enabled briefly during each monostable count. Q1 drives the piezoelectric buzzer, and SW2 disables the buzzer.

Note:

• Experiment with the placement and tilt angle of the mercury switch inside the box: this is crucial.
• Try to get one pulse every two steps. Listening to the beeping sound is very helpful during the setup process.
• Adjust the value of R6 to change the beep power.
• Press P1 and P2 to reset.
• This circuit is primarily suitable for walking purposes. For jogging, extra care must be taken with the placement of the mercury switch to avoid unnecessary counting.
• When the display is disabled, the current consumption is negligible, so SW3 can be omitted.