How would you go about counting the duration of a very small pulse in precision of microseconds ?

 

http://www.electro-tech-online.com/viewtopic.php?t=240

Take a gander at this article.

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I'm no electronics god, i just talk too much.

 

Are you wanting to measure the pulse repetition rate? or the pulse width?

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The great thing about electronics is unlimited ways to do the job. The only limit is one\'s imagination. I generally think my way is best.
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Im looking to measure the pulse width


What about without using an oscilloscope, considering they are costly, are there any other reliable methods :?:

 

How wide is the pulse, and what resolution do you need?

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Ron (aka Rube)

 

0.5 to 2 miliseconds, im going to need to measure several different pulses within that range so it needs to be relatively precise.

 

Would these be radio control servo pulses?.

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An oscilloscope is the first and most obvious tool to use, but it sounds as though you have not got one.
My next choice would be a universal counter/timer. They are expensive and I am guessing that you dont have one of those either.

You could try building a counter/timer if you need to measure the pulse width, a simple one for the times you want is not too difficult. An oscilloscope would be usefull when you are checking the timer.....
OOPS, no oscilloscope! I guess you are stuck.

JimB

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Experience is directly proportional to the value of the equipment ruined.

 

Conect an LED to it an try to count realy fast.

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Il give you shocking experience.

 

Relatively precise means nothing. How you do this depends on a real answer.

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Ron (aka Rube)

 

I think a microcontroller in a counter would work fine. The MCU are known to be faster than most of the fast occuring events, just set to MCU to the desired (sweep) rate and have the result stored in your memory.

 

As Ron pointed out, you need to provide some quantity since the implementation method may depend on that.

For example, what is the _smallest_ width within 0.5ms to 2ms that you anticipate needing to measure? That answer will determine what minimum resolution you will need. And for all your measurments, how close to actual do you really need to be (accuracy)? a +/-1% accuracy for example would mean that if your pulse was 0.5ms long, your design would tell you it was something between 495us and 505us. Assuming you have this kind of resolution of course.

 

eventually radio control but for now Im only treating it as a serial data communicator using PWM between one wire

The smallest pulse width will be 0.5ms, but will be in 0.5ms incriments, 15 times for 15 commands at most. Its hard to predict exactly how much resolution is actually going to be really used in the circuit but I would like an accuracy of atleast 1%

0.5ms * 1% = 0.005ms, isn't that a resolution of 5us ?

so for a value of lets say 1ms I could be off by 1.005ms to 0.995ms

 

Whats the 1st and most accurate method for measuring pulse width ?

Whats the 2nd ?

Any other reliable methods/ideas ?

What about constructing a syncronous 7 segment display clock(probably using 4029's) but clocking it faster than 60Hz, starting with values 1 sec and smaller, and connecting it with a stop/start interface to display how long a specific pulse was, do you think that this method would work :?:

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Thanks for helping me out.

 

I would suggest you use a PIC at both ends, and send digitally encoded data over the link, preferably using Manchester coding (or similar), you can buy licence free radio modules which accept standard RS232 and do the Manchester coding onboard.

Your pulse width scheme looks rather crude and unreliable?, you might like to look at my SIRC's IR tutorial, which uses various pulse widths for IR remore control. You will notice that it doesn't use specific widths, but uses a wide range of widths to represent either START, ZERO or ONE - this gives high reliability.

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PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk