# frequency counter(measurement) circuit development

Discussion in 'Homework Help' started by sadiq_bokhari, Jun 1, 2015.

1. ### sadiq_bokhari Thread Starter New Member

May 8, 2015
11
0
I am working on a circuit it should have 3 input signal types (should be measurable at the same time) and i need to detect their ON-OFF times, the input voltages may range between 0.5V - 40V
something like,
1. pwm motor control
2. frequency convertors
3. relay contacts

the circuit will have an Xmega to do the processing, As my safety elements i am using TVS diodes to limit the voltage upto 40V, and i'm thinking about using SC-filters to do some processing before the data is fed to the Xmega

Kindly guide me about any alternate options for how to work with these requirements. I have some data regarding the specifications, in case of any questions or suggestions i am not able to understand i will consult with my supervisor.

2. ### panic mode Senior Member

Oct 10, 2011
1,425
349
break it down into smaller, manageable tasks and execute them one at a time. i would start with specs such as voltage (already mentioned), frequency range, input impedance etc (nor mentioned). once you know all those, you can start designing input stage...

3. ### sadiq_bokhari Thread Starter New Member

May 8, 2015
11
0
this may sound like a stupid question, but can is use a voltage divider on a pwm signal ?
because my problem is the high voltage, but my primary goal is the measurement of frequency, so if i use a voltage divider on the pwm signal to bring the amplitude within the input limits of the possible ic's i want to use, things would get really easy for me.

4. ### WBahn Moderator

Mar 31, 2012
20,256
5,759
It's hard to say what is reasonable because you haven't given a reasonably complete set of specs and goals.

You might be able to get by with a comparator to turn your input signal into a digital pulse train with a uniform amplitude.