Speed Meter

My child asked me “how fast do I run?”. Well, I said, difficult to say without measuring it. So we started to build a measuring device. I had at home some “waste components”, or better, components I bought hoping one day or another they could become usefull. That time has come.

Let’s start with the list of components:

• No. 1 arduino UNO (or any other device keeping in mind that what follows could require some few changes);
• No. 2 laser emitters KY-008;
• No. 2 laser receivers DS18B20 (that actually may be confusing since the real sensing element should be a ISO203, anyway the latter picture should clarify it);
• No. 2 voltage converters. I used the LM2596 due to the fact I’m pleanty of them, if you have alternatives (linear voltage regulators) of course it’s fine. The use is to convert the 9V from the battery to the 5V required by arduino and the sensors;
• No. 2 9V batteries;
• No. 1 OLED display SSD1306;
• Bunch of wires;
• Wood pieces and cutting tools;

Since the speed should be defined as follows:

The unexpected and brilliant (???) idea is to count the time passing from the moment a body interrupts the ray between the first coupple of TX/RX and the second couple. Knowing the distance between the two receivers shouldn’t be so hard to calculate the speed.