How to double a variable freq

[zhassan]

Hi
I need some help in designing a frequency doubler circuit. The requirement is that i have a signal comming from a motor which starts from 0hz till 1.2khz.
My plans is to quad the I/P frequency (using NAND gates & NOR) and then 1/2 it with a flip flop. Hence getting a doubled frequency.

Firstly i did managed to make a freq doubler circuit with a RC circuit but this can't work on a variable freq because it will overlap freq's.

How can I do this Plz guide

 

[picbits]

There are a few ways.

Have a look at PLL circuits (phase locked loop)
Sample the input frequency with a microcontroller and write some software that varies the output frequency vs input frequency (I have a product that does this for cars)
Use a Frequency to Voltage converter and a Voltage to Frequency converter together

 

[zhassan]

will look into PLL

There are a few ways.

Have a look at PLL circuits (phase locked loop)
Sample the input frequency with a microcontroller and write some software that varies the output frequency vs input frequency (I have a product that does this for cars)
Use a Frequency to Voltage converter and a Voltage to Frequency converter together

thanks for the reply. I'll look into PLL circuits. Why do i have to sample it? the input freq. is a square wave.
Plz let me know if i'm wrong.

 

[picbits]

Those were 4 different ways of doing it. I really should have put bullet points or numbers on them

1. use a PLL
or
2. Use a microcontroller

etc

 

[crutschow]

If the doubled frequency doesn't have to be symetrical you can just trigger a one-shot at the rising edge and at the falling edge of the signal. This will give pulses at double the input frequency.

 

[zhassan]

Thanks

Thats better now. Thanks i'll look into those and let you know if i got stuck.