Please help me in duty cyle detection circuit

[coolstuff07]

Help

Hi,

Please help me in duty cyle detection circuit i.e.,
A duty cycle below 35% is a 0, over 65% is a 1.

Please help me .

Bye.

 

[svhb]

Re: Help me in duty cycle detection circuit

And the frequency of the signal?

Added after 2 minutes:

If you have a stable amplitude, you can put an RC filter on the signal, and compare the signal with 35% and 65% of that amplitude with 2 analog comparators.

Stefaan

 

[coolstuff07]

Re: Help me in duty cycle detection circuit

Hi,

Signal amplitude is constant.

Please can you describe little more.

Bye.

 

[solidstate]

Help me in duty cycle detection circuit

You can use a high speed counter that you gate with your input signal. The resolution you can achieve with that depends on the ratio between your signal period and the smallest period you can handle. The output of the counter is a nice digital value of your duty cycle.

 

[coolstuff07]

Re: Help me in duty cycle detection circuit

Hi,

Iam not able to understand above explanation. Please can any one elobrate.

Bye.

 

[VVV]

Re: Help me in duty cycle detection circuit

If you integrate a signal with a constant amplitude and variable duty-cycle then you obtain a DC voltage that is proportional to the duty-cycle.
So if you integrate your signal you will get a voltage that is different for the two duty-cycles you are mentioning. All you need then is a comparator to distinguish the two levels and produce a logic output.

So, RC filter, follwed by a comparator will accomplish what you need.

 

[coolstuff07]

Re: Help

Hi,

Iam operating circuit at 150Hz.
So, RC filter components sizes
will be huge.

Please any one help if any other option
is there.

Bye.

 

[xulfee]

Help

can u give circuit diagram???????????

 

[coolstuff07]

Re: Help

Hi,

Total system is operating at 150Hz in that i should design a duty cycle detector
circuit. Normal RC filter type circuit is taking huge area. Is there any other alternate circuit.

Bye.

 

[VVV]

Re: Help

I don't really see the problem: at 150Hz the period is about 6.67ms. So if your filter has some 65ms time constant, you should be OK. With ony a 62k resistor you need about 1uF of capacitance. That can be even a surface-mount 0603 for voltages of 6V or maybe even 10V.

I am sure you can use a 555 to discriminate between the two duty-cycles, but let's not forget that the 555 works on the same priciple of RC timing, so the RC values will be of the same order of maginitude.