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19
votes
5answers
5k views

Why can't I see bouncing of a switch on an oscilloscope?

I'm trying to view the bouncing of a simple switch on an oscilloscope. I have prepared a simple breadboard circuit (power → switch → resistor → ground). The problem is, it is displayed as a perfect ...
0
votes
3answers
65 views

How to debounce a low pulse switch for automotive lighting

Hoping you guys can give me a hand with some wiring that I can't quite figure out! Background: I'm trying to rewire a set of automotive lights - these are normally controlled by a computer but I'm ...
0
votes
2answers
77 views

Non-shorting Rotary Switch “dead” Time

Is there a nominal dead time for rotary switches? Obviously all switches are different, so this value will not be precise. For making a reasonable situation, let us assume that a detent style switch ...
5
votes
1answer
198 views

Induced power supply noise on switch contact

I have a circuit that has a 24V section and a 5V section, separated by opto-isolators and an isolated DCDC converter. Both sides of the DC-DC have decoupling caps, and the MCU has one per Vcc pin. ...
8
votes
2answers
2k views

Can multiple Schmitt triggers in series fully debounce a switch?

After dealing with software debouncing for a while, I find it takes a huge toll on the system, so I thought of initially making a hardware debouncer with one Schmitt trigger (74HC14), a capacitor, ...
6
votes
4answers
2k views

Software Debouncing to detect if switch has been pressed for T seconds

I need to detect if a switch has been pressed for longer than a set time, without using any Timer registers in my embedded code. I am using software debouncing in the following manner to detect a ...
0
votes
1answer
141 views

Driving a GPIO input with a momentary switch

I'm looking for a momentary switch (like this one) that can be safely driven by the GPIO pins on a Raspberry Pi 1 Model A (hereafter RPi). This model of the RPi can sustain 3.3V and up to 16mA safely ...
2
votes
1answer
172 views

Switch bounce vs LC Spike Voltage

For my EE lab, our professor wants us to show switch bounce, and then eliminate it using hardware, and software debouncing. However, I seem to be stuck on finding the switch bounce in the first ...
2
votes
2answers
86 views

Wires not making proper contact/interfering

I want to register button presses via a Python program I wrote with a Raspberry Pi 3. My buttons are connected both connected to ground and GPIO pins 22 and 27. However, when the buttons are pressed, ...
0
votes
1answer
136 views

Considerations for debounced power switch with Li-ion battery source

From a battery source, I have connected multiple voltage converters (100V, -1500V etc...). I wish to turn all of this on with a single switch. First of all, will a simple RC filter with large C be ...
0
votes
3answers
440 views

Should I consider debouncing my push button?

Considering a +5V battery source, I have a set of input switches. These switches are push buttons which stay closed upon clicking and open upon clicking again. One side of a switch is connected to ...
-1
votes
2answers
709 views

How does this simple contact debouncing circuit work?

I made a contact debouncing circuit using a capacitor. The main idea was to charge the capacitor, so that the bouncing on the signal would be "smoothed out". It works, but It's been a while since I ...
0
votes
1answer
107 views

Automatic and manual clock managing. Errors with ring counter but not with 4-bit counter

I'm building an 8 bit computer and I've just developed the clock. I used a NE555 (datasheet) with some other integrated (74 series) to manage it. The operator could stop signal from 555 (with a ...
0
votes
1answer
157 views

Toggle switch as momentary with debounce

I have been trying to do the following: When a toggle switch is flipped down, the pic I'm using (16F1503) sends a pulse and turns on a led, when it is flipped up sends the same pulse and turns off the ...
2
votes
3answers
726 views

Where to place debouncing circuit for remote mounted buttons and rotary encoders

I have an application where a push button and mechanical grey-code rotary encoder(user inputs) need to mounted away from main pcb. 24" - 48" away. This is for space and packaging reasons. Is it OK to ...
1
vote
1answer
220 views

USB and button power on solution

I've a circuit that have one input pin that should go LOW if one of two conditions is accomplished: USB is connected; Button OR Switch is pressed/slided; If USB is connected Button or Switch is ...
0
votes
1answer
393 views

Timing diagram of circuit involving switch debouncing

I have a push button switch (single-pole double throw) connected to a latch as follows... I was thinking about the timing diagram of the circuit above (above image is the default state of the circuit ...
5
votes
4answers
3k views

Which diode to use on my RC switch debounce circuit?

I am choosing parts to build an analog RC switch debounce circuit. I plan to implement the circuit described here: http://www.ganssle.com/debouncing-pt2.htm (see "An RC Debouncer"). RC debouncer ...
4
votes
3answers
3k views

Is this a good way to debounce a switch?

There are plenty of debouncing circuits on the internet, but I couldn't really find one that fitted my needs / available parts, so I came up with my own, from what I had. There's nothing special about ...
0
votes
1answer
819 views

RC Schmitt Trigger Debouncing - Cap discharged but there is a voltage across it still

As you can see in the image, I'm running the example given in here where I would debounce the limit switch. I'm running the SN7414 with the given resistors in the diagram. The problem here is that ...
7
votes
3answers
699 views

Debouncing by ignoring data?

All of the software debouncing routines I've seen involve waiting until some number of sequential reads of a signal return 0 or 1. That makes sense, of course. But it means there's an inevitable ...
0
votes
2answers
121 views

Sporadic Clock Signals from Momentary Switch

I'm having trouble using a NO momentary switch to send clock edges to a J-Kbar flip flop, specifically the TI CD74AC109E(datasheet). I have a switch between +5V and the clock pin, and also added a ...
4
votes
1answer
1k views

Choosing transistor for a raspberry pi switch

I'm trying to design a circuit that will control the power to a raspberry pi with a button. The basic usage is: first button press-> rasp powers up. second button press-> rasp continues with power ...
19
votes
1answer
33k views

Is it possible to use just a capacitor to debounce a button?

I have been wondering: why cannot you just hook up a capacitor to a button to debounce it? I have been figuring out how to reduce the work my microprocessor has to do, but I have very limited space on ...
13
votes
3answers
1k views

Physics behind switch bounce when opening?

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 ...
4
votes
2answers
1k views

How to eliminate the forbidden state in an SR latch?

I'd like a latch where the output only changes when both inputs have changed. If only one input has changed, the latch output should stay constant. Here's the state table I want: ...
8
votes
4answers
1k views

Does a switch need to be debounced when opened?

Suppose that an input on a microcontroller has a pullup resistor to 5V and a switch to ground (normally open) connected to it. I know that a switch should be debounced (in my case, in software) when ...
6
votes
1answer
2k views

How is this Pushbutton Debounce code?

I am monitoring a pushbutton with a microcontroller where I am trying to take care of four things together: 50-msec debounce upon push-begin and 25-msec debounce upon push-release identify a short-...