Build Your Pocket Distance Counter!

The maximum range is 9.950 meters with two digits

Place it in your pants’ pocket for walking and jogging

Circuit diagram

Components:

Device purpose:

This circuit measures the distance traveled during a walk. The hardware is housed in a small box placed in a pants’ pocket and the display is designed as follows: the leftmost display D2 (the most significant digit) shows 0 to 9 Km, and its dot remains illuminated to separate Km from hm. The rightmost display D1 (the least significant digit) shows hundreds of meters and its dot lights after every 50 meters of walking. An audible signal (optional), indicates each counting unit, which occurs every two steps. A normal step is approximately 78 centimeters long, so the LED signaling 50 meters lights after 64 steps or 32 mercury switch operations, the display shows 100 meters after 128 steps, and so on. To minimize power consumption, the display lights only when P2 is pressed. Accidental resetting of the counters is prevented because to reset the circuit, both pushbuttons must be operated simultaneously. Clearly, this is not a precision meter, but its approximation degree was considered sufficient for this type of device. In any case, the most critical factor is the placement and slope angle of the mercury switch inside the box.

Circuit operation:

IC1 and IC1B form a monostable multivibrator, providing some degree of freedom from excessive bouncing of the mercury switch. Consequently, a clean square pulse enters IC2, which divides by 64. Q2 illuminates the dot of D1 every 32 pulses counted by IC2. IC3 and 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 activated for a short time at each monostable count. Q1 drives the piezo sounder, and SW2 allows you to disable the beep.

Notes: