In the project 1 to 3 of this article, I explained and built a 0 to 99 two-digit up-counter. The counter is not yet completely finished, but this time I will connect a simple sensor to the up-counter I have made so far, and I will actually try to use the counter.

Push-ups are sometimes performed to increase muscle strength. It is rare for people to do so many push-ups that they cannot remember how many push-ups they have done, but I decided to make a sensor to count them.

Sensor unit for counting push-ups

The circuit for a sensor unit that counts the number of push-ups added to the circuit for a two-digit up-counter that I made is shown in Figure 1.

The sensor for counting the number of push-ups is simply a momentary switch connected to the CLOCK INPUT terminal. A momentary switch is a switch that turns ON only when it is being pushed. The counter section of the unit is not modified in any way.

Figure 1. Schematic diagram with the sensor added counting the number of push-ups

As you can see in Figure 1 above, the hot side of SW3 used for the push-up sensor is connected to 5 V. By pushing the switch, 5 V is input through R9 to the Schmitt trigger circuit consisting of IC3, which becomes the clock signal for the counter.

The sensor is set just below the chin when performing a push-up, and when you lower your arms, your chin is lowered, it touches the switch, turns ON the sensor, which counts "one" push-up.

Making of the sensor unit

The sensor unit simply consists of a momentary switch mounted in a plastic case. Active elements such as transistors and ICs are not used. The sensor unit in which the switch is mounted is a thick-walled plastic box to ensure strength. The switches should be a large pushbutton switch, but it was difficult to obtain them, so four switches were mounted as shown in Figure 2, and an acrylic plate was glued over them to form a single switch.

Figure 2. Making the sensor unit

Operation of the push-up sensor unit

Figure 3 is a free image obtained from an internet search. It is not by the author. The sensor is placed directly under the chin and push-ups are performed. When the arms are lowered, and the chin pushes the switch on the sensor unit, the counter on the unit goes up by one.

Figure 3. Imaginary view of the actual operation of a push-up counter

It is a two-digit counter, so you can do up to 99 push-ups, but looking at the number on the counter is addictive and makes you want to do push-ups over and over again.

CU

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Push-up photo is taken from GAHAG | Copyright-free photos and illustrations.