Introduction: How I Used a Smartphone As a Stroboscope to Stop Time

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This is a simple but a cool hack I made for my kids.

I used a simple Android Application to make a stroboscope effect.

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Safety Notes:

- Please don't use this App in front of young children's eyes.

- Also make sure that those flickering lights will not cause trouble to people seeing them.

- Don't try to touch a fast rotating device even if you see it as moving slowly or stationary. Remember the this is an illusion.


- You can download the App from here.
- You can optionally get a ready made Stroboscope from

Amazon US , eBay , Amazon UK , Amazon DE , Amazon FR , Aliexpress

Step 1: How Does It Work

Stroboscope is a device that flashes at certain rate.

You can use this device to know the rate of rotation of rotary devices such as wheels, fans or anything that rotates.

This is called the stroboscopic effect. It's that effect that causes the optical illusion of wheels rotating backwards.

Step 2: Android Application: Strobily App

Download and Install Application and start it. Make the required adjustments.

Those adjustments are:

Adjusting the blinking frequency -- This one determines how much the mobile flash blinks.

This value is important for detecting the speed of objects. The speed of flash blinking must keep up with the speed of rotation of the object under study.

Adjusting the duty cycle -- This one determines how long the flash remains ON during one ON/OFF cycle.

This value is important for defining the object. The more the flash is ON, the more the object will appear. And the less the flash is ON, the more defined the object appears. This is useful in rotational objects like fans, spinners and wheels.

Step 3: Run the App and Let the Fun Begin

Now it's time to start the App and change the frequency and duty cycle and see their effect on how you see the object.

You can make the spinner or the fan move slower, stop or even rotate backwards as you can see in the video.

And as you change the duty cycle, you can see the spinner arms and the fan blades appear more or less defined.

Change the App settings and have fun.

Thank you for reading.