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Topic: Detecting a change from LOW to HIGH on a pin (Read 3510 times) previous topic - next topic

csnsc14320


When you say delaying is that a fixed delay which in effect is a phase shift. Or is it a micro second extension of the period.


I believe phase shift. We have a 1Hz TTL signal that we want to use to calibrate a detector that can detect photons with microsecond precision. In order to calibrate, we want to be able to delay or phase shift the TTL signal from 1 microsecond to 1 second and synch it up with the detector. So we just need an accurate shifting of the 1 second TTL to compare with to synch it up.

Grumpy_Mike

In that case, I would use a presetable counter that normally runs from the same master clock source. Then when you want to change the phase, output the required number to the counter's preset lines and when the reference 1HZ counter makes a transition arrange the preset value is clocked in. I would probably look into using an RS flip flip to handle the request / acknowledge part of this. It is old school TTL logic but it is your best bet for getting the precision you need.

Photons can go a long way in 1uS.

csnsc14320


In that case, I would use a presetable counter that normally runs from the same master clock source. Then when you want to change the phase, output the required number to the counter's preset lines and when the reference 1HZ counter makes a transition arrange the preset value is clocked in. I would probably look into using an RS flip flip to handle the request / acknowledge part of this. It is old school TTL logic but it is your best bet for getting the precision you need.

Photons can go a long way in 1uS.


Using this method do I still need the comparator, or the arduino even? Or would I be using only the clock generator, the TTL signal, flip flops, and counters?

Grumpy_Mike

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do I still need the comparator

No

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or the arduino even?

Well you have to find a way of inputting the preset numbers. You could do this through a set of BCD switches if you make your clock chain count in decades. Otherwise you can dispense with it and just have a TTL generator.

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