Simple Fatigue Testing Circuit

This small circuit is fun way to check if anyone is tired or not!

It make LED blink very fast.

We can change how fast it blink.

If anyone is not tired can see the light is still blinking even when it goes fast.

But if anyone tired the LED blink will look slow or maybe will not see at all

This happen because our brain does not keep up with fast blink.

If anyone sees fast blink then maybe thy are not so tired.

Circuit Working:

Parts List:

This tired checking circuit uses 555 IC working like astable multivibrator.

It checks how tired person is by seeing how good they see blinking light.

This circuit is easy to make as one LED blinks from 555 IC output.

We can change blink speed using P1 potentiometer.

Blink can go from 20 to 50 times in one second.

People see blink best when it flash around 30 to 40 times per second.

Formula:

This formula show how to find frequency for 555 IC working in astable mode with circuit above:

F = 1.44 / (R1 + 2R2) × C

where,

• F is frequency in hertz (Hz)
• R1 is resistor R1 value in ohms (Ω)
• R2 is resistor R2 value in ohms (Ω)
• C is capacitor value in farads (F)

This formula think duty cycle is almost 50%.

That mean how long output stay ON compare to full cycle time.

How to Build:

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

Connect the 555 IC:

• Put 555 IC on breadboard.
• Pin 1 connects to ground and pin 8 to power (VCC).

Make astable setup:

• Connect pin 4 to VCC which turn off reset.
• Connect pin 2 and pin 6 together.
• Connect pin 6 to pin 7 with 10k resistor.
• Pin 7 connects to ground using a potentiometer.
• Connect pin 6 and pin 2 with 0.1µF capacitor.

Connect the LED:

• Long leg anode of LED connects to pin 3 of 555 using 390Ω resistor.
• Short leg cathode connects to ground.

Add potentiometer:

• One side of 100k potentiometer P1 connects to VCC.
• Other side to ground.
• Middle pin wiper will connect to pin 7 of 555 IC.

Give power to circuit:

• Connect power supply
• Connect positive to pin 8 of VCC.
• And connect Negative to ground.

Change the blink speed:

• Turn potentiometer P1 to change blink speed of LED.
• LED can blink between 20 to 50 times per second Hz.

Optional: Add switch and box:

• One can add switch to turn ON/OFF easily.
• Put everything in box to keep safe and clean.

Test circuit:

• Turn ON the power and observe the LED.
• If LED blink fast and one can still see it maybe he not tired.
• If LED blink fast and one cannot see the blink then maybe he is tired.

Note:

• Be careful while working with electronics.
• If one is not sure about electronics ask someone who knows better.

Conclusion:

To conclude this Simple Fatigue Testing Circuit use blinking light from oscillator usually 555 IC.

It make LED blink at different speeds.

By checking when person stop seeing the blink we can guess how tired they are.

If they do not see fast blink maybe they are more tired.

This way circuit gives simple and useful way to test tiredness using eyes and fast light.

References:

 Fatigue test equipments and (b) circuit diagram