This fatigue testing circuit is very simple and easy to build and will determine how tired a person is. It has been discovered that the highest light frequency that a human can detect is negatively influenced by his fatigue. This circuit is based on 555 timer that is connected here as an astable multivibrator. Its output is connected to a LED that is flashing with a certain frequency.
With P1 potentiometer that frequency can be adjusted between 20 and 50 Hz. The highest flashing frequency the humans can detect is somewhere between 30 and 40 flash per second but a test made by us in a early morning produced some questions like: “What LED?”
To make a reliable fatigue test you must adjust P1 when you are not tired. So, adjust P1 untill you just start not seeing the LED light. Leave it like that and then power up the circuit when you are tired and you will notice that the LED light has gone :).
Because of the fatigue tester circuit nature, there is no wonder it has a small current consumption of just 25 mA so you can powered it up from a 9 V battery. Do not consider this to be equal to fatigue testers found on the market.