30
votes
Accepted
Smart ways to detect a button (less power consuming)
A low-current method I used once was to connected a switch between two microcontroller I/O pins.
One I/O was configured as an output (SWO). The second was configured as an input (SWI) with its ...
- 23.8k
30
votes
Long-distance Arduino buttons crosstalk over Cat5e cable
The point of the twisted pair is to have a signal and its return on the pair. Using the two halves of a pair for an unrelated signal is an unintended use, and the tight twist of the two halves ...
- 20.6k
28
votes
Accepted
How does the telephone's keypad work?
There is a conductive pad on the bottom side of the button that "shorts" out the spiral. Usually dark grey since it is carbon based.
The spiral just give you a higher probability that the pad will ...
- 47k
26
votes
Smart ways to detect a button (less power consuming)
A SPDT (Single Pole Double Throw) button would be your ultra efficient button.
Source: http://www.ni.com/white-paper/3960/en/
In your case the 1P would go to the MCU, the 1T to VCC, the 2T to GND.
- 8,249
20
votes
Accepted
What's the purpose of a tactile switch with GND pin?
ESD from fingers is diverted to shield for 15kV test.
Confirmed in spec
• Ground terminal available to protect against static
electricity.
• Beware path inductance 1nH / mm (typ) and avalanche ...
- 148k
16
votes
Can multiple Schmitt triggers in series fully debounce a switch?
Can multiple Schmitt triggers in series fully debounce a switch?
A single Schmitt trigger with a analog filter in front of it can be used for debouncing. However, after that Schmitt trigger, the ...
- 315k
15
votes
Accepted
Software Debouncing to detect if switch has been pressed for T seconds
I have managed to complete the aforementioned task using timers, however, since then, I have used all timer registers (and match resisters that are available) for more important tasks within the same ...
- 178k
15
votes
How can I reuse this set of buttons from an old Sky cable TV box?
It would be much easier to understand if you rearrange schematic like this:
simulate this circuit – Schematic created using CircuitLab
Now you can see that by applying voltage to IO1 you can ...
- 13.1k
13
votes
Accepted
Can multiple Schmitt triggers in series fully debounce a switch?
Using Schmitt triggers in series would not further reduce bounce.
Consider the filter:
The input is (U). The red line is a 50% threshold, the output of which is seen as signal (A). It bounces each ...
- 5,242
11
votes
Is it possible to use just a capacitor to debounce a button?
I think the accepted answer said that you can only use an RC trick to de-bounce a switch that is tied to low, but I think that is not true. You can do it for high as well. Here is the schematics. ...
- 1,669
11
votes
Accepted
Push Button with Voltage Rating (AC) : 125V, Only having power supply of 3.5 or 5V
Your question is wisely asked. In general, an AC-rated switch should be derated for DC use. AC ratings are usually higher than the DC rating, if available, for the exact same switch. There's a reason ...
- 78.7k
11
votes
Smart ways to detect a button (less power consuming)
One method I have used takes advantage of the capacitive nature of CMOS inputs.
simulate this circuit – Schematic created using CircuitLab
In the circuit above the switch, when closed, allows ...
- 47k
11
votes
What kind of tactile switch is this?
This is a familiar feature in DSLR shutter controls- partial press for focus and full press for shoot.
Here is a lower profile switch from (major Japanese switch manufacturer) ALPS. They call it a &...
11
votes
What do dashed lines mean in the schematic?
Here is a similar switch with a different way to show the states:
I would prefer they didn't show the arrows on pins 1 and 6 in OPs diagram, it makes it a bit ambiguous.
There are other similar ...
10
votes
Smart ways to detect a button (less power consuming)
How long will the button be pressed? If it is not a toggle switch (which keeps its state) but a momentary switch then the current flowing when the button is pressed is largely irrelevant due to the ...
- 81.4k
10
votes
Accepted
Button debounce ringing
The ringing is caused by poor layout (possibly breadboarding is the worst culprit) AND the fact that your button's switch-contact is shorting out a charged capacitor - the instantaneous current flow ...
- 473k
10
votes
How do input pins work?
Setting pull-up or pull-down switches an internal resistor (or something similar) between the input pin and either Vdd or GND.
So you effectively have either of these:
simulate this circuit – ...
9
votes
Smart ways to detect a button (less power consuming)
If your button is a piezo switch, then the only power required is the power generated by pressing the button.
For example: R2/C1 collect the energy produced by pressing the piezo. D1 prevents the C1 ...
- 3,421
9
votes
Long-distance Arduino buttons crosstalk over Cat5e cable
Since you probably don't need ultra snappy response to the buttons, I'd first try adding simple RC filters to the switch lines. Ideally on the microcontroller side but I think you'd still get benefit ...
- 485
9
votes
Accepted
Buttons that do not bounce or scopes that pretend to be 100 MHz but actually aren't?
Should I worship the buttons for magically being bounce-free or
should I mistrust my scope? The scope did show me 100-nanosecond sized
events, so I can't really find evidence of fault with it.
On a ...
- 27.6k
9
votes
Accepted
What do dashed lines mean in the schematic?
It looks like the solid lines are the connections in the "normal" or unpressed state and the dashed lines are the connections in the pressed state. The datasheet may state this explicitly.
- 23.1k
8
votes
Accepted
Differences between Interrupts and sampling for hardware button?
Debouncing is a FAQ. You should be able to find... nearly unlimited numbers of web pages on the topic. Smith commented about Jack Ganssle's widely read PDF on the topic, as well. And with all these ...
- 78.7k
8
votes
Accepted
Clarifying an article on switch debouncing - something about leakage current causing trouble
Mr. Ganssle is saying that the worst-case leakage current (if it comes out of the input) multiplied by the R2 resistor value could result in the input voltage not getting close enough to ground when ...
8
votes
Accepted
How can I reuse this set of buttons from an old Sky cable TV box?
That is a button matrix which is read in a multiplexed fashion. Very common arrangement, almost everything that has many buttons like your PC keyboard or TV remote has a similar matrix.
General ...
- 172k
8
votes
Accepted
Detecting the push button outside the loop function in Arduino
delay() is generally bad programming except for very simple applications as it ties up the processor.
Use the elapsedMillis() library function instead. In use you ...
- 180k
7
votes
How does the telephone's keypad work?
The spirals are electrical contacts. Shorting the traces in a spiral causes the keypress to be detected.
The backs of the keys have a layer of conductive rubber or plastic. Pressing that layer ...
- 73.5k
7
votes
Automated test for pushing a pcb mounted mini push button
Instead of using the actuator to push the button, arrange something with a limited force to push it, like a weight or a sprung lever. Then use your solenoid to pull it back. This allows you to use any ...
- 174k
7
votes
How can I reuse this set of buttons from an old Sky cable TV box?
Connect IO4, 5 and 6 through resistors to ground. Hold just one of IO1, 2 or 3 high, and read IO4, 5 and 6.
If you look at your schematic, you should see how for all possible combinations of button ...
- 47.1k
7
votes
Accepted
Using relay (no microcontroller) for turning on/off power
A simple low-cost solution would be to just use a push-to-on / push-to-off switch to control the power.
There would be no need for a relay.
- 19.2k
Only top scored, non community-wiki answers of a minimum length are eligible