Hot answers tagged

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 ...
user avatar
  • 17.6k
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 ...
user avatar
  • 13.7k
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 ...
user avatar
  • 45.6k
25 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.
user avatar
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 ...
user avatar
17 votes
Accepted

What's the purpose of traces that are later punched out?

Actually, if you look closely you see that many of these holes connect switch channels with their common signal (ground or supply). So this is simply to test the fabrication of the FPC itself, before ...
user avatar
  • 18k
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 ...
user avatar
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 ...
user avatar
  • 164k
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 ...
user avatar
  • 10.3k
13 votes
Accepted

Rubber push-button

It's a silicone rubber keypad. They're usually custom-made for the application (MOQ in the thousands or more if a mold has to be made). They require a matching PCB that is either gold-plated or ...
user avatar
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 ...
user avatar
  • 4,927
12 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 ...
user avatar
  • 68.8k
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 ...
user avatar
  • 45.6k
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 &...
user avatar
10 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. ...
user avatar
10 votes
Accepted

How does this button work without any circuit closing device?

The gold plated interlocking concentric "rings" are two contacts of a switch. When they are electrically connected by a resistance of less than say 10 k Ohms the circuit is activated. The white "...
user avatar
  • 142k
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 ...
user avatar
  • 78.7k
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 ...
user avatar
  • 378k
9 votes

Understanding interrupts and software button debounce

Torsten, yes, introducing a 40ms delay into the ISR is a wrong idea. Usually, buttons are polled in the main() loop. Interrupts are good when you have to detect an event with a very small latency, ...
user avatar
  • 35.9k
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 ...
user avatar
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 ...
user avatar
  • 475
8 votes

What's the purpose of traces that are later punched out?

Another possibility is to disable features when assembling a "lesser" model. So you can use the same PC or flex circuit for a range of models and decide which options to implement during manufacture.
user avatar
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 ...
user avatar
  • 68.8k
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 ...
user avatar
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 ...
user avatar
  • 87.1k
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 ...
user avatar
  • 159k
7 votes
Accepted

Replace 5-pin push button in my laptop

The switch is probably a SPST-NO tact switch with an earth connection to the metal top (for ESD protection reasons). The earth connection would be the center connection on the right. If you want to ...
user avatar
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 ...
user avatar
  • 57.4k
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 ...
user avatar
  • 140k

Only top scored, non community-wiki answers of a minimum length are eligible