# falling/rising edges for a wide voltage range

Discussion in 'Homework Help' started by sadiq_bokhari, May 15, 2015.

May 8, 2015
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I need a circuitry to detect the falling and rising edges of voltage signals [square waves, probably PWM signals] ranging between 0.5V - 40V at a resolution of maybe 10us (10 micro seconds)
the data(voltage amplitude and on/off times) are to be fed to a micro-controller (probably from the Atmel Xmega family)

any guidelines about where i should start looking to design such a board ?
p.s. i guess its gonna be something like the circuitry of an oscilloscope

2. ### MikeML AAC Fanatic!

Oct 2, 2009
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Is the gain adjustable, or does it have to work with any pulses between 0.5 and 40V without adjustment or gain switching.

Quantizing 40V with a 10bit AD would mean a resolution of 40/1024 = 39mV

May 8, 2015
11
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for this, i will have to confirm with my instructor

4. ### WBahn Moderator

Mar 31, 2012
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Do you mean that a given square wave signal is going between a low value of 0.5V and a high value of 40V, or do you mean that your system needs to work today with a square wave that is 0.5V in amplitude and tomorrow with a square wave that is 40V in amplitude?

5. ### Alec_t AAC Fanatic!

Sep 17, 2013
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Are you trying to measure the slope of the rising and falling edges, or merely detect at what instants the edges occur, or pass a threshold voltage?

May 8, 2015
11
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I think its going to fluctuate between the values of 0.5V - 40V i mean it could be like 2V or 36V at different times

May 8, 2015
11
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Its the second one, i have to detect the instants at which they occur

8. ### WBahn Moderator

Mar 31, 2012
18,087
4,917
You might try using a peak detector to establish a reference for your upper level and then a voltage divider to establish the reference level for your comparator.

What is the frequency of this PWM signal? Is that fixed or can that vary, too? If so, over what range?