What is Switch: Definition and 562 Discussions

In electrical engineering, a switch is an electrical component that can disconnect or connect the conducting path in an electrical circuit, interrupting the electric current or diverting it from one conductor to another. The most common type of switch is an electromechanical device consisting of one or more sets of movable electrical contacts connected to external circuits. When a pair of contacts is touching current can pass between them, while when the contacts are separated no current can flow.
Switches are made in many different configurations; they may have multiple sets of contacts controlled by the same knob or actuator, and the contacts may operate simultaneously, sequentially, or alternately. A switch may be operated manually, for example, a light switch or a keyboard button, or may function as a sensing element to sense the position of a machine part, liquid level, pressure, or temperature, such as a thermostat. Many specialized forms exist, such as the toggle switch, rotary switch, mercury switch, push-button switch, reversing switch, relay, and circuit breaker. A common use is control of lighting, where multiple switches may be wired into one circuit to allow convenient control of light fixtures. Switches in high-powered circuits must have special construction to prevent destructive arcing when they are opened.

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  1. R

    Best path for a switch to Computer Science?

    I have a BS in Mechanical Engineering and I've been out of school for almost 5 years. Several months back I started learning Java just for kicks, but I've reached a point where I'm pursuing more and more knowledge of CS concepts on my own, and the interested level is far exceeding that of...
  2. D

    How Can I Improve My Spark Gap Switch for High-Speed Photography?

    Hi everyone , this is my first post here :) . I am an auto electrician , my hobby is photography. I am interested in high speed photography and have invented a new form of photography in a way . I call it 'superspeed photography' . It involves taking a picture of something that is triggered by...
  3. S

    Simple switch that Remembers state at power up?

    Simple switch that "Remembers" state at power up? I've been trying to design a switch that, when a relay (spdt) is energized: -if a reed switch is closed, a 12v green light bulb drawing 2.5A stays lit until the relay is de-energized, regardless if the contacts of the reed switch open/close...
  4. H

    Searching for a 12v electronic switch

    New to the site, looking for a little help. I'm trying to switch my motorcycle auxillary lights on and off using the flash to pass switch. I have a relay but only stays on when powered. Is there a switch I can put inline, or a switching relay that will work. Thank you
  5. K

    Construction of a Timer Switch

    Hi, I'd like to do a small design project. When I sleep, I switch on my mosquito repellant for about 8 hours. Sometimes I forget switching it off too. Such long durations are little poisonous and generally not required. What I plan to do is to make a timer with a dial from 0 min to 60 min...
  6. L

    Switch to chemical engineering or stick with biochem?

    Hi everyone, my first post on here. I was hoping someone might have a few words of advice/suggestions. I'm a current sophomore currently pursuing biochemistry/molecular biology. My goal is to work in drug development of some sort, at a biotech company or so. Basically, I like to design and...
  7. C

    Detect switch without a complete circuit?

    Hello everyone! I have a bit of an engineering puzzle. I've only a passing understanding of electrical engineering, so still trying to puzzle if out. Basically, imagine you have one black box A connected, via a single wire with a switch, to black box B. There is no returning wire. The...
  8. M

    Need help adding a on off IR LED/Phototransistor as switch

    I'm building a small project and would like some assistance from you folks. I have this motor 5rpm -12vdc and I'm using a Class 2 plug in transformer (input 12VDC 60Hz 23W - output 12VDC 1000mA) to power it up. I would like to add a IR LED/Phototransistor between the two to act as a on off...
  9. G

    Program Switch Comp Eng - Comp Sci

    Hello, I am currently in my Second year of Computer Engineering, but I often find myself not enjoying the electrical engineering courses that we have to take (Electromagnetics, Microelectronics, Circuits and Systems) but I immensely enjoy the programming courses and the Computer Engineering...
  10. Femme_physics

    Engineering Electronic circuit with Op-Amp, Switch and Diodes

    Homework Statement http://img689.imageshack.us/img689/6668/mycircuit.jpg Given a circuit that includes Operational Amplifiers, double-switch - S, for two situations, 1 and 2. Type of switch - DPDT - Double pole double throw. Two diodes and two lightbulbs, L1 and L2. Given: Voltage...
  11. D

    How hard is it to switch fields?

    How hard is it to switch fields in science? For example, say you do your Ph.D. in an area of theoretical physics and are very successful, but cannot find further funding at some point (can't land a postdoc in your chosen field, no professorship offers, denied tenure, etc.). How difficult would...
  12. R

    I need a 12v switch to respond to a 433.92 Mhz signal

    Im not an elctrical engineer but I do need a source for the above mentioned switch. I would even be open to a simple schematic. Please Help.
  13. S

    Engineering Question about the BJT as switch circuit

    [b]1. Homework Statement my teacher wants me to design a circuit to control the on or off of 4 BJTs in the circuit. Homework Equations The Attempt at a Solution so i tryed to control a BJT at once .. it workshttp://user.qzone.qq.com/259234914/infocenter#!app=4 but there were...
  14. D

    How to Wire a Momentary N.O. Switch to a Battery Operated Device

    Can anyone tell me how to wire a momentary normally open switch to a battery operated device (4 AA batteries) like this one? http://www.scientificsonline.com/mini-plasma-ball.html Is it even possible? Any advice appreciated!
  15. N

    Programs Switch after PhD from Nuclear to Medical Physics?

    I think after completing my PhD I want to make a switch to medical physics. With my background (described below) this shouldn't be too great of a switch. (I wish I had realized this sooner, as in undergrad I was thinking biomedical engineering, but found myself far more interested in the...
  16. O

    How can i use 5V to switch 24V on/off?

    I'm working on a project that uses a joystick to control a motor. The motor has an electric motor brake built in, and I want to be able to engage/disengage the brake with a button on my joystick. The motor runs on 24VDC, and the joystick runs on 5VDC. I currently have the button on the...
  17. B

    Maximizing the Power of 555 Timers: Creating an On-Off Switch for Your Computer

    Hello!So recently I've been playing with 555 timers. And I am beginning to understand how powerful they can be.With that reset pin switching capabilities are endless. But that led me to thinking.How can I make that switch, which you have at your computer, that power on and off switch. The switch...
  18. S

    Why is my MOSFET switch not behaving as expected?

    I have the following circuit wired up on a protoboard. The datasheet for the BSS138 MOSFET is here. I'm puzzled regarding what I'm seeing happen with this circuit - when I apply 3.3V at the gate resistor, the MOSFET turns on fully and I see 3mV at the output. This, of course, is expected...
  19. B

    Inductor, switch, snubber diode(flyback diode)

    Hello, I am designing a simple circuit and I need some guidance over snubber diode. When we open the switch, when we have a inductor in circuit, we will have that arc over switch which is something that we don't want. Using this snubber diode, we can avoid this. I feel that we will...
  20. S

    Clap Switch using 555 timer in monostable mode(Values of components))

    Hello Experts! Here is my simple clap switch schematic. First let me know is it correct or not? I have used 555 timer in monostable mode here this means LED will remain on for the particular period of time defined by R3 and C1 i.e. T=1.1(R1)(C1). Let I use red LED here. So I think 1.7V is...
  21. S

    Interpreting MOSFET ID/Vds curve for a MOSFET Switch

    Hello, I'm considering using a logic-level MOSFET as a switch in a design. The drain of the MOSFET will be connected to an IC. The IC works at 3.3V and the maximum voltage at which it's guaranteed to read a low is just 0.8V. Now, I think every MOSFET will able to satisfy this but I'm just...
  22. S

    Clamp switch (Working of components)

    Clamp switch using 555 timer in monostable mode(Working of components) Hello experts! Here is my circuits in the attachments.(Monostable mode of 555) All values of components shown here have been chosen by myself and all are arbitrary. I want to ask some question about this circuits. i.e...
  23. P

    Choosing a capacitance to limit voltage across a switch

    Hi everyone. My problem is for an assignment in a network analysis course. I attached the homework page as a pdf. Homework Statement My problem involves an R-L circuit with a switch. There is a 100 V source, and switch that is initially closed, followed by a .25 H inductor and a 200 Ohm...
  24. T

    12 volt switch from 5 volt supply

    Hello Please my apologies for mistakes as I am a new member, and I would like to ask a how to question,I am trying to make a system up that I can use on my racing cars ( classic hence no onboard computer ) What I want to do is to have a 12 volt pulse(from 12 volts to o volts) that I can use on...
  25. O

    Switch the divergence coordinate system

    Homework Statement i have the divergence in the (x,y,z) Cartesian as \frac{dA_x}{dx}+\frac{dA_y}{dy}+\frac{dA_z}{dz} and the assignment is to transfer it to cylindrical system (r,{\phi},z), by any way i choose. Homework Equations tried with the chain rule, but i am doing...
  26. S

    How does a debounce switch work?

    i recently had a lab where i needed to build a circuit with a debounced switch in it. now i have to explain how the debounced switch works but I'm having trouble articulating the different operations that occur. the circuit consisted of two wires each with a resistor of the same type and...
  27. K

    Is Switching from Engineering to Physics Worth It? A Personal Perspective

    So I've been contemplating switching my ME major to physics for months now, and I'm still having trouble deciding. I really love physics, but I don't want to regret switching. I've read in some sources that Physics majors are extremely employable, while some claim that it's a worthless major...
  28. F

    Building a 6V DC Circuit Switch for Rapid On/Off

    I have looked everywhere for help with this, and I can't find any. I am trying to construct a mechanism that will rapidly switch a DC circuit on and off, anywhere from 10 to 100+ times a second. Ideally this switch should consume as little power as possible, and should be powered by a 6 volt...
  29. M

    Engineering How to Calculate Voltage Across a Capacitor in a 2-Position Switch Circuit?

    In the circuit below, the switch reaches a steady state while in position 1 then at t = 0 gets thrown to position 2. I am supposed to find the voltage (s-domain) across the capacitor under these conditions using thev. theorem I just want to make sure I am approaching the problem with the...
  30. N

    Solving Micro Switch Problems: Maintained vs Momentary

    i am in no way a engineer so i need help i just bought (MICRO SWITCH, PIN PLUNGER, SPDT 16A 250V; Microswitch Type:Standard; Actuator Style:Pin Plunger; Operating Force Max:100gf; Contact Voltage AC Nom:250V; Contact Current Max:16A; Switch Terminals:Quick Connect; Circuitry:SPDT) and it...
  31. P

    Designing a Temperature-Activated Timer for Grain Storage Fans

    Hello knowledgeable ones! I need your help to make my life easier; Background. I need to turn on fans every cold night during winter in a grain storage shed to keep the grain from heating/rotting! This involves treking to the shed in the cold after midnight (cheap electricity) and...
  32. C

    Continue with Aerospace Engineering or switch to Astrophysics?

    I'm a second year Aerospace Engineering student and I'm wondering if this is the best career path for me to take. Since a young kid I've always been fascinated by the universe and everything related to it. I want a career that will let me progress our knowledge of space forward whether it's via...
  33. N

    Any 4 from 8 switch permutation

    Good evening to all I wonder if anyone can help please I have 8 switches b1,b2,b3,b4,b5,b6,b7,b8 I am trying to work out how many permutations I would have if I pressed any 4 of the 8 switches ie if I pressed b1,b3,b,7,b8 to make a circuit or it could be b3,b5,b6,b7 doing it by long hand I...
  34. D

    Switch ratings conversion from AC to DC

    I have a push-button switch rated at 3 amps @ 125vAC which I want to use in a 12v DC application (my motorcycle). ((on ground line under continuous use {headlight})) Does the AC rating translate as 3 amp for 125v AC hence 375 watts 375 watts for 60v AC hence 6.25 amps or 375...
  35. S

    Using MOSFET in Saturation (as a switch)

    I'm trying to learn about MOSFETs in order to use them as a switch. (note: this is not a homework/school question). On my breadboard, I have the following circuit hooked up: I vary the gate voltage using a potentiometer. Here is what confuses me: according to wikipedia, the MOSFET is in...
  36. D

    Looking for hardware software interface to emulate mechanical switch

    I am a wheelchair user trying to find a way to trigger certain functions on my chair from a PC. Basically what I have right now is a switch like this: http://www.enablemart.com/Catalog/Sensitive-Switches/Micro-Light-Switch My goal is to emulate that switch with a software program, which of...
  37. C

    2-Capacitor, 2-Resistor Parallel RC Circuit with Switch

    Homework Statement For the attached circuit (which I've drawn rather poorly in GIMP), I need to figure out the charge on each capacitor when the switch has (a) been closed for a long time and (b) been open for a long time. Homework Equations Loop and Junction rules, \DeltaV=IR...
  38. L

    BJT switch temperature compensation

    Is there a way to minimize the temperature dependence of VBE. I am trying to design a BJT switch, that will turn on at a particular voltage(43v). ckt attached. The base sees 0.65v when Vcc is 43v or more (resistor divider bias). This turns on the BJT. It should be off when Vcc is 42V or...
  39. M

    Can I use one switch for two power sources on my robot?

    Hello, on my robot I essentially have two sources of power. #1. The first is my 9-volt battery to the BS2. (+ pin 24, - pin 23) #2. my second is a power source for the motors. it uses four C batteries not directly connected to the stamp but with it's own system of circuitry. check...
  40. Z

    Transitioning from Physics to EE: Is it a Logical Switch and How Can I Prepare?

    I am entering into graduate school next year and strongly considering going from a bachelor's in physics to a Master's EE program. One of my main reasons for doing so is that I am interested in more tangible hands on work as opposed to more computer coding based tasks and intense theory. Does...
  41. Femme_physics

    Electricity: Basic circuit question with a switch

    This is a question that was on my test Homework Statement http://img269.imageshack.us/img269/5125/circuitthingy.jpg In the circuit in the drawing switch S is open. Both resistors are idential, both having resistance R each. Given the source is E, and R = r (the resistance of...
  42. H

    Switch for 220V AC & Battery - 12V DC Output

    Hi I am looking for off the shelf switch which can handle both 220v Ac and Battery(dc). output of the switch should be 12vdc, when powered by AC it should automatically cut the DC and start Charging the battery and rectify AC to DC. Please help.its really imp for my project.
  43. M

    Finding/Implementing a digitally-controlled high-voltage switch

    I am looking for a switch or relay to switch high voltages on and off based on a digital input signal. Below are the characteristics of the device I would like to find. Switching frequency: 100 Hz to 100 KHz Input (control) signal: square waves, 3 to 12 volts amplitude, 100 Hz to 100 KHz...
  44. L

    BJT PNP Switch: Why Vee Must Reach Zero for On

    In a BJT PNP switch, why does the base voltage need to go to zero to turn it on. If Vee is 5V, the base has to be 5-0.7v to make the BE fwd biased.
  45. O

    Opening switch on inductor circuit in absolute vacuum

    So, a professor in class a about a year ago mentioned that opening a switch in a circuit that an inductor is providing power to would cause a breakdown in the air and a spark would jump across it because the current can't change instantaneously to zero in an inductor. Something just made me...
  46. B

    On/Off Alternating Direct current other than a power switch?

    Hello, I would like to know if there is a part I can buy that will alternate my dc power circuit on/off at short intervals automatically All help much appreciated, Cheers, Nick
  47. Topher925

    How to eliminate arcing in a switch?

    I'm working on a project where I'm connecting a big 36V battery to some electronics which contain capacitors on the power input. Of course when I connect the two I get some major arcing which likes to weld and stick connectors together. Does anyone know of a simple or easy way around this? The...
  48. Y

    IT and I want to switch to Astrophysics

    Hello everyone, I hope I'm writing this in the right forum. I am so desperate for guidance == Long story short == I have a BSc in Information Technology and I want to get into astronomy and astrophysics for graduate school. how can I make this shift in fields? do I have to go...
  49. rhody

    TED Video: Ed Boyden: A light switch for neurons

    Interesting http://www.ted.com/talks/ed_boyden.html?utm_source=newsletter_weekly_2011-05-17&utm_campaign=newsletter_weekly&utm_medium=email", I thought I would pass it on. Ed Boyden shows how, by inserting genes for light-sensitive proteins into brain cells, he can selectively activate or...
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