- #1
Furion
- 3
- 0
Ive been working on a new project for my studies but can't seem to get any info on 'switch bounce'
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SUMMARY
Switch bounce refers to the electrical noise generated when a mechanical switch closes, causing multiple rapid transitions between on and off states, typically lasting around 40 milliseconds. This phenomenon can lead to erroneous signals in digital circuits. Switch debounce is the technique used to eliminate switch bounce, often implemented using NAND gates or by introducing a delay in microcontroller interrupt service routines. Understanding the distinction between switch bounce and switch debounce is crucial for effective circuit design.
PREREQUISITES- Basic understanding of electrical circuits
- Familiarity with mechanical switches
- Knowledge of digital logic principles
- Experience with microcontrollers and interrupt service routines
- Research "NAND gate switch debounce circuits"
- Study "mechanical switch characteristics and behavior"
- Learn about "implementing debounce in microcontroller programming"
- Explore "interrupt service routine best practices for switch inputs"
Electronics students, hobbyists working with microcontrollers, and engineers designing reliable switch interfaces will benefit from this discussion on switch bounce and debounce techniques.
- #2
Antiphon
- 1,685
- 4
It's the electrical noise made by metal coming together to form a circuit. It lasts maybe 40ms depending on the switch.
Google "switch debouncing circuit" and you'll get lots of examples.
Google "switch debouncing circuit" and you'll get lots of examples.
- #3
dlgoff
Science Advisor
Gold Member
- 4,441
- 3,264
If you are interested in cleaning up switch bounce (switch debounce), you can do it with a couple of nand gates.
http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/setreset.html"
http://hyperphysics.phy-astr.gsu.edu/hbase/electronic/setreset.html"
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- #4
Furion
- 3
- 0
Is switch bouncing and de bouncing the same?because I am not sure
- #5
Feldoh
- 1,336
- 3
Switch debounce and switch bounce are two different things.
Switch Bounce happens when you close a mechanical switch. When you close a switch it tends to literally bounce upon the metal contact which connects the circuit.
It's almost like dropping a basketball. The basketball will hit then ground (analogous to a closed switch) then bounce back up (analogous to a open switch) then bounce back down, then up, then down, etc... until it permanently stays on the ground (permanently closed).
Usually switches take a few microseconds to a few milliseconds to completely close. What this means in terms of digital logic is that as the switch physically bounces your logic can switch back and forth low-to-high-to-low-etc... until your switch settles down.
Switch Debounce is the process of getting rid of switch bounce. One solution to get rid of switch bounce is given above by dlgoff
Switch Bounce happens when you close a mechanical switch. When you close a switch it tends to literally bounce upon the metal contact which connects the circuit.
It's almost like dropping a basketball. The basketball will hit then ground (analogous to a closed switch) then bounce back up (analogous to a open switch) then bounce back down, then up, then down, etc... until it permanently stays on the ground (permanently closed).
Usually switches take a few microseconds to a few milliseconds to completely close. What this means in terms of digital logic is that as the switch physically bounces your logic can switch back and forth low-to-high-to-low-etc... until your switch settles down.
Switch Debounce is the process of getting rid of switch bounce. One solution to get rid of switch bounce is given above by dlgoff
- #6
MATLABdude
Science Advisor
- 1,663
- 6
If you are doing microprocessor/controller work (e.g. with an externally-triggered interrupt), it's quite common practice to pause for a period of time (~20 ms or so) upon receiving an input in order to debounce a button / switch / relay.
A friend of mine nearly tore his hair out trying to fix an interrupt service routine where he'd forgotten to do this.
A friend of mine nearly tore his hair out trying to fix an interrupt service routine where he'd forgotten to do this.
- #7
Furion
- 3
- 0
ohh I get it now make a lot sense now thanks guys