How to make a lap counter

Many times, we want to know how many laps a wheel has done, or we simply want to keep track of activities, such as jumps, hits, etc. In this article, we will see how to make a lap counter which we can convert into a general counter, using the electronic addition principle of a calculator.

Electronic calculator


- An old calculator.

- A switch.

- Cables.

- Tin soldering iron.

- Silicone sealant

Arming our accountant

The first thing we are going to do is open the calculator, remove the circuit board from the case and locate the equals (=) key contact.

calculator circuit board

Once we have identified the two terminals of the equals (=) key on the circuit board, we mark them with a pair of toothpicks so as not to make a mistake when closing the circuit, as this would spoil our project.

identification of contacts

Then, we turn the board over and position ourselves where the terminals are, identify the points to which we have placed the toothpicks and with the help of a tin soldering iron, we solder a pair of wires to the contacts of the equals (=) key.

circuit board

Now, very carefully, we pull out the soldered terminal wires from somewhere on the calculator and close the case. To prevent the case from opening, we can use silicone as a glue.

Welding of cables

Next, we connect the wires to a switch, this can be a simple electronic switch or a magnetic switch, it all depends on our imagination and what we want to tell.

Electronic counter

This small device can be modified to become even a small kilometre marker for a bicycle or for counting steps while walking, or for any other activity we want to keep records of with a counter.

How it works

The way it works is simple, in calculators there is a little trick: when we press the 1, then the + key and then the equals key (=), an infinite counter is generated, similar to the one used in programming. Each time we type equal (=) one more unit will be added to our count and so on until we stop.

By removing the terminals and connecting them to a switch, we are closing the circuit in an external device that we can manipulate at will, to take advantage of this little trick of electronics and generate a digital counter of 8 digits in a very short time.

0 thoughts on “Cómo hacer un contador de vueltas”

  1. For transformer rewinding it does NOT work, it does not count when the turn is fast. ....

    1. Frankyarango26

      it depends on which microphone you use because it worked for me with a high end microphone and of course it has a limit but if it's fast it's about 3 per second and if you use a good motor you get more out of it. 

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