buttondebounceswitches
I was surprised to learn that a mechanical switch (SPST) bounces when it is opened. What causes the contact to temporarily return to touching?
Does this phenomenon only happen with certain types of switches (e.g., with sliding switches but not with most pushbuttons)?
Well, I have a idea which may not be the best but you can use it if you don't get those switch. Have you tried using acrylic sheet ?? thats a very good and neat option and you can get the job done with less number of led's & less power consumption.
as its very easy to work with these sheets and for better illumination around the switch etch the acrylic sheet, Its going to look gr8 :)
I think you are asking what can be added to the switch input (actually your IR sensor) to make it act like a single pulse trigger and not a continuously held switch. To do this you can just use the same method you are already using between your existing 555's, use a capacitive input, (see below).
You may need to adjust the R1,C1,C2 values a bit to get the timing just right, and the original 33k pull-up might also need to be higher. Ultimately you could even include a buffer or one shot in-line with the first 555 to give you a better input pulse shape. If you look into 555 applications there should even be a circuit to use a 555 as a one-shot.
As another alternative you could use a tri-state buffer gate and enable it with an output of one of your 555's. That arrangement would temporarily disable the input signal and create a single pulse, (see second circuit).
simulate this circuit – Schematic created using CircuitLab
Best Answer
Basically no substance is perfectly smooth, or inelastic. When two objects come together with any force, there is kinetic energy that needs to die down upon contact. So you get some "ringing", plus since the surface isn't smooth the contact makes/breaks a bit randomly until settling (e.g. even with a sliding switch the contact resistance will vary upon movement)
It happens with all switches; sliding, pushbutton, relay, etc, though sliding or wetted contacts (e.g. mercury) are better. It also happens upon opening the switch, not just on closing. Some are better than others - you can get some awful ones that will bounce for tens of ms, and some good ones that settle within <5ms.
To add more on the opening of the switch, it's due to the irregular surfaces opening in a not perfectly perpendicular manner. The widely varying resistance this creates appears similar to the bounce during closing. When pressure is released, one part of the contact may disengage, but another part may briefly obtain a lower resistance than it had previously, the more irregular the surface and the more of an angular force between the contacts, the more pronounced this effect is likely to be.
Although it looks smooth to our eye, the copper surface looks rather different under a microscope: