When I toggle a push button switch on and off, instead of getting a pure on/off continuity levels I sometimes get "transitional" values. I need it to be purely on/off with nothing in between. What components do I need to add to the switch to make that happen?
There is +5 V being applied at what is labeled "TIP".
Here is am drawing of the original circuit I am trying to replace:
Mechanical switch contacts "bounce" both when making and when breaking. Bounce is when the contacts make partial, higher resistance contact or bang into each other repeatedly and very quickly. It is common for contacts to make and break 5 or 10 or even 100 times in a few milliseconds. Depending on the circuit the switch is driving, this can be taken as an intermediate voltage or as 100 really fast clock pulses.
The standard way to fix this is to "de-bounce" the switch with an electronic circuit. Two common methods are 1) any one of a group of circuits that essentially act as a lowpass filter; or 2) have the switch input clock a flipflop. Once a "1" is clocked into the flipflop, multiple successive clocks have no affect. With this method, you have to reset the flipflop before it will respond to another button press.
All you need is cap. such that the RC=T exceeds the bounce time using the large internal pullup R.
The contact closure gives a low RC attack time and the release a slow decay time to act as a Sample and hold for as many milliseconds to cover your transitional time.
Logic and software can also do the same thing with edge detection with a timeout.
But if you introduce a series string of binary weighted R's, the the MSB R weighted value will swamp the value of all the others.
The only solution then is to use software averaging and choose analog thresholds to discriminate which combination of switches are active. You then have to deglitch by averaging or look for successive values in a 5% window of full scale for a duration > max transitional time.
The issue you are facing (or more accurately the solution) is called 'debouncing'. Google it and you will find answers.
When a physical switch closes, and applies a voltage that goes from (let's say) ground to 10V (or whatever), at first there is intermittent conduction. Think of it as microscopic sparking, until a solid circuit is formed. Then it is solid at 10V.
usually, a capacitor (with or without a resistor) across it will do the trick.
So in the circuit there is +5v being applied to what is labeled as "IN". So each button push is to provide a different return voltage level to the device it is plugged into.
– Brak Sep 14 '17 at 16:25So everything works perfect.... except for the bouncing (thank you all for giving me the term) giving "transitional values".
– Brak Sep 14 '17 at 16:29