Electronic Pedometer for lap counting

Using an Electronic Pedometer for lap counting

An alternative to electromechanical counters is an electronic pedometer - "step counter" - or whatever the supplier chooses to call them. These are intended for clipping on to you trousers to automatically count how may paces you've walked and are sometimes available for as little as a pound each.

A typical pedometer A typical example of a pedometer.

The counter, display and reset button are already there, all you need to do is connect it up to your track. Remove the back and you'll find some electronics and some sort of switch to sense movement. In the example (see photo below) there's a pendulum on a light spring that makes contact when it is in the down position (right hand half of photo).

inside a pedometer Inside the back of a pedometer

To make it count laps all that is needed is one wire from the pendulum and one from the contact going to a pair of normally open relay contacts connected to the lap counters - as shown in the diagram below. It is advisable to keep the relays fairly close to the counters - this sort of electronics may play up if you start connecting yards of wire to it. I've had no trouble with up to a foot of wire (30cm).

Pedometers come with their own batteries - usually a small "digital watch" type (see photo above) These will probably last for ages, but it may be worth connecting up a power supply to replace a the internal battery. The normal single cell type batteries provide about 1.2 volts. This can be conveniently supplied by a couple of diodes (1N4001, IN4002, or 1N4003 etc.) in line with a 470 ohm resistor from the main track power supply as shown below. It's always wise to check the pedometer battery voltage with a voltmeter before connecting the supply to make sure that its supplying to correct voltage and is connected the right way round!

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