is it possible to make a electronics variable frequency 555 timer? I came across it when I reading about 555 timer but don't know how to implement it.

 

Go to the top of the page.
Click on Vol VI
Choose hysteretic oscillator.

 

I wrote this!

555 Hysteretic Oscillator

The 555 Projects

 

sorry, my bad English, what I really mean was electronically variable frequency 555 timer, one that can change frequency without physical interaction.

 

sorry, my bad English, what I really mean was electronically variable frequency 555 timer, one that can change frequency without physical interaction.

Not quite sure if this is what you're looking for, but they make Digital Pots.

 

It looks to me like what you have to do is change the voltage on pin 5 to alter the frequency, and it can be done electronically.

 

The term you are looking for is a VCO, Voltage Controlled Oscillator. A 555 can do this, but not very well.