Simple Fatigue Testing Circuit

This circuit is a fun way to test how tired you are!

It works by flashing an LED light really fast.

You adjust the speed of the flashing.

When you are well rested, you should be able to see the light flickering even at high speeds.

But as you get tired the flashing might seem to slow down or even disappear.

This is because your brain has trouble keeping up with the fast light.

The faster the flashing light you can still see, the less tired you likely are.

Circuit Working:

Parts List:

This fatigue testing circuit based on a 555 IC operating as an astable multivibrator is designed to measure a persons level of tiredness by determining their sensitivity to light frequency.

The circuit is simple to construct, with a flashing LED connected to the 555 IC output.

By adjusting the frequency using the P1 potentiometer, the circuit can generate flashing frequencies between 20 and 50Hz.

Human sensitivity to light frequency peaks between 30 and 40 flashes per second.

Formula:

The formula below is used to determine the frequency of a 555 IC set up in astable multivibrator mode through the above diagram:

F = 1.44 / (R1 + 2R2) × C

where,

• F is the frequency in hertz Hz
• R1 is the resistance of resistor R1 in ohms Ω
• R2 is the resistance of resistor R2 in ohms Ω
• C is the capacitance of capacitor C in farads F

The duty cycle, or the ratio of the output waveforms peak time to its overall period, is assumed to be close to 50% in this calculation.

How to Build:

To build a Simple Fatigue Testing Circuit, you need to follow the below mentioned steps:

Connect the 555 IC:

• Place the 555 IC on the breadboard.
• Connect pin 1 to ground and 8 to the positive terminal of the power supply, respectively.

Set up the astable multivibrator configuration:

• Connect pin 4 to VCC to disable the reset function.
• Connect pins 2 and 6 together and connect them to pin 7 through a 10k resistor.
• Connect pin 7 to ground through a potentiometer.
• Connect pin 6 to pin 2 through a 0.1µF capacitor.

Connect the LED:

• Connect the anode longer leg of the LED to pin 3 of the 555 IC through a current limiting resistor 390Ω
• Connect the cathode shorter leg of the LED to ground.

Add the potentiometer:

• Connect one end of the 100k potentiometer P1 to VCC the other end to ground and the wiper to pin 7 of the 555 IC.

Power the circuit:

• Connect the positive terminal of the power supply to pin 8 VCC of the 555 IC and the negative terminal to ground.

Adjust the frequency:

• Use the potentiometer P1 to adjust the flashing frequency of the LED.
• The frequency can be adjusted between approximately 20 and 50Hz.

Optional: Add a switch and enclosure:

• If desired, you can add a switch to easily turn the circuit on and off.
• Enclose the circuit in a suitable enclosure for safety and convenience.

Test the circuit:

• Power on the circuit and observe the flashing LED.
• The flashing frequency can be used as a measure of fatigue as higher frequencies may be harder to detect when fatigued.

Note:

• Exercise caution when working with electrical components and high frequencies.
• If you are not familiar with electronic circuits consider seeking assistance from someone with experience.

Conclusion:

To conclude, a Simple Fatigue Testing Circuit utilizes an oscillator often a 555 IC, to flash an LED at varying frequencies.

By determining the threshold at which a person can no longer perceive the flashes the circuit provides a simple yet effective method for assessing fatigue levels based on visual sensitivity to high frequency light.

References:

 Fatigue test equipments and (b) circuit diagram