Relay Definition and 143 Threads

A relay is an electrically operated switch. It consists of a set of input terminals for a single or multiple control signals, and a set of operating contact terminals. The switch may have any number of contacts in multiple contact forms, such as make contacts, break contacts, or combinations thereof.
Relays are used where it is necessary to control a circuit by an independent low-power signal, or where several circuits must be controlled by one signal. Relays were first used in long-distance telegraph circuits as signal repeaters: they refresh the signal coming in from one circuit by transmitting it on another circuit. Relays were used extensively in telephone exchanges and early computers to perform logical operations.
The traditional form of a relay uses an electromagnet to close or open the contacts, but other operating principles have been invented, such as in solid-state relays which use semiconductor properties for control without relying on moving parts. Relays with calibrated operating characteristics and sometimes multiple operating coils are used to protect electrical circuits from overload or faults; in modern electric power systems these functions are performed by digital instruments still called protective relays.
Latching relays require only a single pulse of control power to operate the switch persistently. Another pulse applied to a second set of control terminals, or a pulse with opposite polarity, resets the switch, while repeated pulses of the same kind have no effects. Magnetic latching relays are useful in applications when interrupted power should not affect the circuits that the relay is controlling.

View More On Wikipedia.org
  1. EmmyBamidele

    Can someone recommend a relay for me?

    I have a 30V - 100A power supply that I want to control using a -/+ 10V NI DAQ. I want a relay between the current output of DAQ and the power supply. Please advise the specification of relay to use. I'd appreciate a comment on how to connect it also.
  2. Next_Of_Kintetic

    How can I reroute multiple signals from a 4 pin connector using a relay switch?

    Hi, First off, I want to say that I'm basically a noob when it comes to electrical engineering; I have some knowledge and took an intro to robotics course in college, but if I knew the answer to this question, then I wouldn't be here asking haha. So here it is: From what I know, relay...
  3. CAMTWO

    Flyback Voltage Spikes Emitted From an Unprotected Relay

    I research the phenomenon and came up with the fact they weren't using protected diodes in their relays they utilize in a multitude of wiring harnesses for cars and also go into factory built kitcars in massachusettes.. I was having huge issues and have accrued over $1000 in blown sensors and...
  4. PainterGuy

    European data relay satellite system

    Hi, I was watching the following video. So, a low Earth orbit continuously transmits data to a geosynchronous satellite via a laser link. The geosynchronous satellite relays the data to a ground station on Earth via a radio link. In case of European Data Relay System (EDRS) laser communication...
  5. P

    3 Phase Harmonics and Solid State Relay Issues

    I have a 3 phase problem that I think might be applicable to this forum. The setup is equipment which contains 5 resistive heaters (A through E). The unit is powered by 208V 3 phase and each of the heaters are hooked up line to line in an unbalanced configuration as follows: L1-L2: Heater D...
  6. V

    Samsung double door fridge overload relay changed 3 times in 2 weeks

    Hi Guys, I am new to this forum. I request an expert opinion cause I've not found anything relevant on the web search. I have a Samsung double door refrigerator. Two weeks ago, it stopped cooling and clicking noise coming from the overload relay box plugged into the compressor. I took out...
  7. M

    PID or Relay for Circulating Shower

    I am considering using PID (autopid arduino lib), in order to control the heat, with PWM and a 50amp mosfet heating a 40amp 24v heating element in a 3litter tank, but I am thinking, that since the water is going to be circulating, and sometimes losing heat to a person, sometimes falling straight...
  8. L

    Could Tin-Plated and Nickel-Plated Contact Materials Cause Relay Failures?

    Trying to troubleshoot a field failure on a purely resistive load on a 30A rated relay utilizing only a 24A load (cycled off/on for 45 min, 1x/day). Our wiring/load has been verified but this failure has been occurring sporadically but impact has been large. My question is, could a tin-plated...
  9. C

    What Are Suitable Alternatives for 4-Leg and 5-Leg Ronway Relay Switches?

    hi can anyone here recommend an alternative relay switch x2 one has 5 legs one has 4 im not able to find any the same :( and the ones I've looked at all have 5 legs the diffrece is Ronway RWG1-DC12V-HS and Ronway RWG1-DC12V-ZS Any help is appreciated :) hs and zs is the only diffrence i can see...
  10. srinaath

    Arcing in electrical relay contacts due to different types of loads

    Arcing in a contact occurs due to open and close action of the switch. I am curious if the arc intensity depends on the type of load. For example the arcing (arc intensity) due to induction load will be greater than arcing due to resistive load?
  11. F

    Relay and Capacitor circuit - blinking LED

    Hello Forum, I am having issue understanding what is going on with the circuit below which is supposed to blink an LED by alternatively pulling the switch up and down which results in opening and closing the circuit the LED is part of (lower circuit portion). This is what I am confused about...
  12. D

    How to build a radio relay station?

    if i decide to build two relay stations 100 miles apart, what frequency or frequencies should i use to send a radio signal across 100 miles from 1 relay station to the other relay station.
  13. S

    Solving Power Delivery Issues in a 5V Series Circuit with a 1.5V Rated Relay

    Hello, I'm using a "TQ2SA-1.5V Panasonic 2 Form C AS Single side stable, 1.5VDC 2A DPDT NON-LATCHING SMD Relay" (specifically the coil side of this relay) that is rated for 1.5 volts that is connected in series to this circuit (as the last device in this circuit shown below), which in this...
  14. shushi

    Novice question about Relays, Capacitors, and Diodes

    Hello, In regards to this relay, TQ2SA-1.5V Panasonic 2 Form C AS Single side stable, 1.5VDC 2A DPDT NON-LATCHING SMD Relay https://www.mouser.com/ProductDetail/769-TQ2SA-1.5V PDF 1 of Relay PDF 2 of Relay (specifically pages 5-6) is attached at the bottom as a pdf file. I was previously told...
  15. BlackPowder

    Electrical Massive Relay Control: Do I Need 100 I/O Ports?

    Is there any solutions for a micro controller to control massive amount of relays, such as 100 of them? Do I really need 100 I/O ports for this circuit? I can make one master MCU with couple slaves to get many I/O ports. But I think there must be some better way to do it.
  16. J

    Controlling 10 mA Relay with Opening/Closing Switches

    Can opening and closing switch turn on and off 10 ma relay
  17. adamaero

    Replacing two corresponding switches as one with AND-gates

    Homework Statement So this is not homework or an assignment, but usually my questions get moved here anyway. This is from a project I'm working on for my job. A user can choose between DPDT functionality (so having "SensorI" be a doorway that goes up and down, reverse) or add another sensor in...
  18. srinaath

    Current rating for an electromechanical contactor

    I have a elctromechanical contactor (contactor is an electrically operated switch - It is larger version of relay) which has following specification, Inductive full load current - 30A Resistive full load current - 40A Why is rated inductive current less than rated resistive current?
  19. sn9434

    Relay Insulation: Microsemi BR246-S0233 - Why Resistance Changes?

    I have Microsemi BR246-S0233. As is, the resistance between the X2 (GND) and signal line (e.g. A2) is OL. However, when I power it up (X1 = 25VDC), leave it for 5 minutes and power off, then straight away measure the resistance between X2 (GND) and the signal line A2, the resistance is now...
  20. H

    Alternative to Relay for Accurate Time Measurement Experiments

    I am carrying out a physics experiment to measure g by free fall using an Arduino. This experiment requires accurate time measurements of upto a millisecond. I am using a relay to turn on/off an electromagnet and there is a maximum lag of 10ms due to the relay. I am a complete beginner. Please...
  21. H

    Motorcycle starter safety circuit

    I don't know if it's the same for a car but bikes uses a starter relay to set off a starter motor which cranks the engine. Bikes have a side stand for you to lean the bike against when stationary. In case the rider tries to start the bike with side stand deployed (could cause crash if forget to...
  22. H

    Why do we need a switch before a relay?

    So in high current circuits which involve say a starter motor in a car we need a starter relay since a normal switch cannot handle the high current flow. I think the reason I'm asking this question is because I don't understand what exactly makes the relay be able to handle the current unlike...
  23. William123

    Switching high voltages with arduino and a relay

    Hello I came across this video on youtube where a guy was switching a lightbulb on and off with an arduino and a relay (). I was bothered by how he left out the phase wire (look at the image at 4 mins and 53 sec in). People mostly seem to be complaining about how he is breaking the ground...
  24. F

    Relay with High DC Breaking Capacity

    Hello! I have to use a relay to operate circuit breaker opening/closing coil i.e. 80W @ 110VDC. Since the breaker is having some mechanical interlocks, so sometimes when the coil is operating, the breaker may not open. In that case the relay contact has to make & break the opening/closing coil...
  25. L

    Can I use a relay to wire DC lights to a speaker?

    I want to wire some LED strips to the bass speakers in my car so that they will light up to the music. I reason that you can't wire the lights in parallel with the speaker because the lights can blow with too much volume. I also read that it will trash the sound quality. ? Anyway, my plan is to...
  26. Nikhil N

    What is the meaning of "110V AC / 24 DC relay"?

    I have seen some relays mentioned as 110V AC/ 24V DC relay. Is this means, can I use both 24DC and 110V AC to the coil of relay?
  27. Nikhil N

    How to check the condition of coil in the relay?

    I am using the relay as chatter. That is I am continuously on-off the relay to produce bursts. I am using 12V DC relay. I got voltage upto ~120V while it is switching very fast initially. Now I am not getting high voltage while switching. I am getting only ~10V. What may be the reason? Is it...
  28. Nikhil N

    Noise due to chattering of relay

    I need to know how to couple noise due to chattering of relay? I have seen the below method to couple. But I want more detailed circuit to do this. Please help me. Also I want to know where the tremendous amount of EMI can be seen ? Is it across the coil of relay?
  29. C

    Boolean Expression for Relay Contacts and Lamp

    Homework Statement In the diagram, Y006 is a lamp, and X & R references are relay contacts. Write down a Boolean expression for the lamp to light. Homework EquationsThe Attempt at a Solution This is what I have done as an interim step to help me visualise what's going on: This is the...
  30. srinaath

    Understanding Relay Ratings for Controlling Motors: A Comprehensive Guide

    hi am planning to buy a electromechanical relay with following specification: 16A 256VAC 60HZ, 3PDT this relay is used for controlling a heater. heater's specs are 2000W 256VAC I have found one matching for this spec from TE.. its specs are 16A 256VAC switching capacity: 6000VA what does...
  31. I

    Understanding Spark in Relay Contacts: Causes and Solutions

    Why is there a spark in the relay contacts? Suppose that the coil and the contacts are connected to two different power supplies. If i suddenly disconnect the power supply to the coil, then the voltage across the coil will increase and a spark will jump across the switch that I used to...
  32. X

    Relay Driving Circuit Design Help

    Hello all! I hope I am posting this in the right place. I am looking for some help on the following circuit. Basically I am doing a relay application using one of TI's chips. Below is the reference design from an app note along with my actual circuit modeled in TINA. The main function is that...
  33. J

    Calculation for Earth fault relay

    Dear friends,May I know how to calculate the Earth fault relay/ Earth leakage relay? When we going to use them? Thank you.Regards, Jason
  34. A

    Diode Use in Relay: Why & How to Protect Op Amp

    Why reverse diode is used in relay ?? In my book its written that ,to protect op amp from damage but how does it protects?
  35. T

    Choosing Relay for 5V DC & 12V Motor

    I have a 5v dc circuit and a 12v dc motor. If I had to use a relay, when looking at the specifications, what do I look for ?, will the coil voltage be 5v and the switching voltage be 12v ? Will these relays work ? http://www2.mouser.com/Electromechanical/Relays/_/N-5g31?P=1z0x3tdZ1yyfbg3...
  36. E

    How exactly does a plunger relay work?

    Hi, I'm new to relays. As I understand it, there is a coil which creates a magnetic field to cause the armature to move (such as a plunger) and closes the contacts of another circuit. My question is this - how can the AC cause the plunger to move? isn't the AC producing sinusoidal B field, which...
  37. S

    Reverse relay and travel limit switch - PLC

    Homework Statement Hi, I'm currently studding a module on PLC and have a question on "what will happen if you do this ...". Homework Equations I don't have a problem with explaining operation of each rungs of the ladder diagram, I need some help on explaining the function of the reverse relay...
  38. S

    Reverse relay and travel limit switch - PLC

    Hi, I'm currently studding a module on PLC and have a question on "what will happen if you do this ...". As I don't have a problem with explaining operation of each rungs of the ladder diagram I need some help on explaining the function of the reverse relay and travel limit switches. Can anyone...
  39. T

    Electronic component type (what would do this?)

    I was going to make a modem uninteruptable power supply, and I was thinking (possibly over complicated) that I could have a relay with the solenoid that has a potential over the battery bank and the power supply, so there would be near zero volts potential when the power supply was on (and...
  40. H

    How do you read the ratings of a relay?

    Hey guys, hopefully this is the right subforum.. Anyways, I am wondering how to read the ratings of a relay. Here is what I am looking at: http://www.ebay.com/itm/5pcs-5V-T73-SRD-5VDC-SL-C-5Pin-10A-Relay-Module-Arduino-ARM-PIC-AVR-DSP-/161755474571?pt=LH_DefaultDomain_0&hash=item25a960aa8b...
  41. B

    How Can You Protect Your Motor with Relay 542 Plus?

    motor protection relay , thermal overload,unbalance,under voltage, Earth fault,
  42. G

    Is There a Sensor to Detect Current Change and Turn on a Relay?

    I'm trying to figure out a way to turn a relay back on with a sensor. This relay is attached to a device that is plugged into a wall. I was thinking of using a non-invasice current sensor but I don't know if there will be a significant current change, if any, once I turn the device on, if the...
  43. A

    AXIS P1355 Camera I/O + relay to turn on light/garage door

    here is the manual http://www.axis.com/en/files/manuals/um_p1355_49956_en_1303.pdf see page 61 Notes: i have seen this thread https://www.physicsforums.com/threads/axis-camera-with-i-o-and-relay-to-turn-on-lights.538043/ but this camera is a bit different i think as it has digital inputs and...
  44. P

    What Are Some Options for Programmable Home Automation?

    I want to switch either a standard AC socket or a USB outlet on and off on a programmed cycle. But although there are many consumer-ready timers available to do this at set times of day, programmable to the minute, I want to be able to randomize the cycles and have it programmable to the second...
  45. L

    Arduino and DC Solid State Relay 'Flicker'

    Hi, thank you for your help in advance. I have a circuit configured as shown in this image. I got this arrangement from an earlier thread. An arduino controls a DC solid state relay, and it works fine when my load is a simple LED. The arduino is controlling through a digital output header and...
  46. L

    Help interpreting schematic with relay

    Hi, thank you for your help. I am having fun experimenting with an arduino. I have a solid state relay (SSR) which I am learning to use for the first time. I have found things sort of confusing, but have found the following image at the Arduino playground useful: Image here Here is what I have...
  47. Gordo

    Arc Suppression for Fuji PXR4 Micro Controller

    DPST Power relay has 120VAC coil & 40A contacts (resistive) ratings. A Fuji PXR4 Micro Controller is triggering the relay; the load is a 220V pottery kiln element. The contacts are arcing (but not bouncing) at make & break on nearly every cycle. The above relay just replaced a previous SPST...
  48. P

    Plotting of relay current curves

    When Plotting relay current curves using log paper, I understand that all curves should be plotted on a common base voltage (converting currents accordingly) and the curves can be cut at the maximum fault current level that the device is likely to see (corrected to the base current). What I...
  49. A

    Is there a way to keep an LED turned on even when the power source is off?

    Hi, I'm looking for a device like a transistor which preforms the opposite. E.g. On an NPN when Base is +0.7V current can flow through the Collector to the Emitter and when the voltage at B is 0V (i.e. a switch connected to base is open) no current will flow from C to E. I want the opposite of...
  50. S

    Solving a Question on Relay with IGCSE Physics

    [PLAIN]http://[url=http://postimg.org/image/pwudznwxd/][PLAIN]http://s16.postimg.org/pwudznwxd/image.jpg Hello everyone, I'm new to this forum. I'm glad that there is a forum for physics as there are questions that I try to solve but to no avail , I hope to find the answer here. I study IGCSE...
Back
Top