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What is debounce?


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#1 JerryTX

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Posted 01 July 2010 - 02:47 PM

So your marker has debounce and your not really sure what it does? Here is the quick explanation.

In a typical scenario where debounce is involved you have a trigger that when pressed is actually pushing a button (normally a microswitch) inside the trigger frame. When the marker is on this switch completes the circuit which indicates to the marker to fire.

Since these switches have a spring, when you push the button there is a tendency for switch the bounce. This can cause the switch to contact and lose contact with the the metal inside the switch that completes the circuit.

Also, a circuit continually loops and runs it program until powered off. So, the board is continually reading (many times a second) the state of the switch. As you're starting to see, this bouncing can cause the board to believe many shots have been "requested" within a very narrow window of time.

Note: This is a problem with mechanical switches so this problem is not specific to paintball markers, etc.

The accepted practice of fixing this problem is the concept of debounce. Debouncing simply means when the state of the switch changes (IE, off to on or on to off) to wait for a predetermined amount of time before checking for the final/actual state of the switch.

So the debounce setting basically tells the marker board how long to wait until getting that final state of the switch to avoid misreading these bounces.

Without debounce:
Scenario A: I start to press the trigger causing bouncing; marker fires multiple shots.

With debounce:
Scenario A: I start to press the trigger causing bouncing but I realease before the debounce time; circuit detects the switch is not pressed; nothing happens.
Scenario B: I start to press the trigger causing bouncing but I continue with my trigger pull during the debounce time; circuit detects the switch is pressed; marker fires!

Now this scenario is over simplified because the boards offer a lot of additional programming to consider modes of fire, ramping, etc. But basically, you get the idea.

If you want a more sensitive trigger lower the debounce if you want a more predictable trigger increase the debounce. But also keep in mind that there are other factors in terms of how quickly the marker can cycle (IE get ready for the next shot) and a debounce that is too low could result in misfiring issues.

Edited by JerryTX, 01 July 2010 - 02:54 PM.

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#2 brycelarson

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Posted 01 July 2010 - 05:53 PM

nice writeup.




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