Presented here is a simple pedometer circuit. It measures the distance covered by you while walking. It may not work very well for running!

Circuit and working
Fig. 1 shows circuit diagram of the distance counter. The circuit is built around quad 2-input Schmitt trigger CD4093 (IC1), CMOS ripple carry binary counter/divider CD4024 (IC2), decade counter/divider CD4026 (IC3 and IC4), two transistors BC327 (T1, T2) and some other components.

Fig. 1: Circuit diagram of the distance counter
Fig. 1: Circuit diagram of the distance counter
Fig. 3: An actual-size, single-side PCB for the distance counter
Fig. 3: An actual-size, single-side PCB for the distance counter
Fig. 4: Component layout for the PCB
Fig. 4: Component layout for the PCB

Download PCB and component layout PDFs: click here

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Gates N1 and N2 of IC1 form a monostable multivibrator that receives trigger input from tilt or mercury switch S1. When you lift your foot up and touch the ground back during walking, the mercury inside the switch makes a contact with its two metallic leads as shown in Fig. 2. This makes the current to flow between the metallic leads and a pulse is generated at pin 4 of IC1.

Fig. 2: Open-close operation of mercury switch
Fig. 2: Open-close operation of mercury switch

This pulse is fed to pin 1 of IC2 that produces a divide-by-64 counter. Its output is given to inputs of gate N4 of IC1 and the output of N4 is fed to the base of transistor T2 through resistor R8. Transistor T2 drives the decimal point segment of common cathode 7-segment display (DIS1).

IC3 and IC4 are configured as decade counters to drive the 7-segment displays DIS1 and DIS2, respectively. Switch S4 resets these two counters and switch S5 enables DIS1 and DIS2 displays.

Transistor T1 drives the piezobuzzer (PZ1), which beeps after every two steps (one stride), provided switch S2 is closed. DIS1 and DIS2 displays indicate the distance covered in metre (m) and kilometre (km) units, respectively.

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