Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [switches]

Devices to interrupt or route a signal or power one of several ways.

Devices to interrupt or route a signal or power one of several ways. There are mechanical (manually operated), electromechanical (mechanical, but electrically activated: relay) and electronic switches.

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Why does a resistor need to be on the anode of an LED?

Please be kind, I am an electronics nub. This is in reference to getting an LED to emit photons. From what I read (Getting Started in Electronics - Forrest Mims III and Make: Electronics) electrons flow from the more negative side to the more…
Spechal
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Why do some tactile switches have 4 terminals?

I am wondering why some tactile switches have 4 terminals instead of two? For example, take a look at these switches, like the image below: (source: pranelectronics.com) What is the use of the two remaining pins? If the pins of the exact opposite…
rajat
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When to use pull-down vs. pull-up resistors

After learning and experimenting with microcontrollers, I've understood the concept of pull-up- and pull-down resistors. I now understand when and how to use them, and how they work. I've mainly used pull-ups because I was taught to, but it has…
osvein
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Fan speed switch: why OFF :: HIGH :: MED :: LOW?

Many AC fans, including inexpensive floor models, have a rotary speed control which rotates from OFF to HIGH to MED to LOW. Since the switch does not rotate 360°, you have to rotate it backwards to shut it off. This has always slightly annoyed me,…
RichF
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Why do you need 2 resistors when hooking up a transistor as a switch

What is the point of R2 in the following diagram: I get that R1 controls the current to the Base, but what does R2 do?
Tyler DeWitt
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What's the difference between field-effect transistors (FETs) marketed as switches vs. amplifiers?

For instance, the J108 JFET is listed as "N-Channel Switch", and the datasheet mentions the RDS on resistance, while the J201 JFET is listed as "N-Channel General Purpose Amplifier" (and the on-resistance would have to be deduced from the IDS…
endolith
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How can I wire a 9-position switch so that each position turns on one more LED than the one before?

I have a 9-way switch like this guy: And I'm trying to figure out how I can turn on one LED with position 1, 2 with position 2, all the way up to all 9 in position 9. Obviously I can repeat all the wiring for the LEDs at each position, but that…
Isaac Lubow
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How do I fix an Omron d2fc-f-7n microswitch from unwanted clicks?

Omron d2fc-f-7n microswitches are used in computer mice all around, and they eventually start clicking several times per hit. AFAIK there is a flexible metal plate that wears out due to metal fatigue, so there must be a way to prolong its life. The…
user1306322
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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 a PCB I am designing, so I don't want to do a…
Anonymous Penguin
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What is the purpose of "MOSFET driver" ICs

There are dedicated "MOSFET driver" ICs available (ICL7667, Max622/626, TD340, IXD*404.) Some also control IGBTs. What is the practical purpose of these? Is it all about maximizing the switching speed (driving gate capacitance) or are there other…
XTL
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How do I make the turn off and turn on time equal in a NPN transistor?

I have a simple NPN switch, see the diagram. I feed a 100KHz square wave (TTL) to the base of this transistor and it turns on very very fast (a few nSec) but it doesn't turn off as fast, it almost takes 2uSec for it to turn off. (I am looking at…
Frank
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Three legged NOT gate? What is this symbol?

I've come across the above schematic in a datasheet for a 4x2:1 bus switch. What exactly does that triangular symbol on S mean? It looks a lot like a NOT gate, but the third leg is confusing me.
Bo Thompson
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Why do we need a voltage divider when we get the same voltage at the output as the input?

I am using a voltage divider circuit of 100 Ω and 10 kΩ resistors, and using their output for the (IRF740) transistor's input. I'm trying to figure out why do the resistors have those specific values. It makes sense that if I use voltage divider, I…
Edi
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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 square/rectangle on the scope. I have attached a…
Deniz
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Make a momentary switch control a toggle

What are the simplest, cheapest, smallest ways to make a momentary switch produce a 2-state toggling output (latching momentary switch)? In other words, the output is continuously low, and when you momentarily press the button/tact switch, the…
endolith
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