Talk:Relay

Sugestion for External Link
To whoever is "managing" this page, may I suggest an external link to the "Heath Robinson Rube Goldberg (HRRG) Mixed Technology Computer" project at http://www.diycalculator.com/sp-hrrgcomp.shtml. The idea is to create a computer out of a mixture of implementation technologies, including relays, vacuum tubes, transistors, simple integrated circuits, pneumatic logic, magnetic logic, and so forth. — Preceding unsigned comment added by Memyselfmax (talk • contribs) 21 February 2007 (UTC)
 * Just an FYI. No need to ask to add something. The person who is "managing" this page is you (well everyone that is). Good link idea so I am adding it. 69.72.2.72 01:48, 17 March 2007 (UTC)

Contact Rating
There seem to be two ratings for contact current: Carry current and Switching current. I think it would be useful to define these terms.

-JKoether

Italy
hello

I have a problem related to a special tipe of relay, used in Italian railway, called "disk relay".

This tipe of relay has two solenoids, with two SINUSOIDAL currents, I' and I", and the force on an aluminium disk depend on the current intensity and the phase of two currents. The force is proportional on this formula: C= K*I'*I"*sen(a)  (*), where a is the angle of phase between sinusoidal current I' and I".

The couple C must be more than a particolary minimum value: if this is not, the relay go "down", and this is an alarm. This tipe of relay is used to misure the returned current from the field in a circuit that control the free/not free state on a railway track: current I' is local, current I" is from the field.

Due to the presence of the angle a in the couple formula, the retourned current must have a phase angle strictly on a specific range, around 90°.

Well, this description is the antefact, the answer that I don't know is another: If I apply another type of current to the disk relay, for example, not sinusoidal, but for example rectangular pulses, how can I modelized the value of the force C on the disk?

With the Fourier transformer, I can divide the pulses on the disk with more sinusoidal pulse, with frequencies f, 2f, 3f, etc..

I can say that the force C must be C= C(f) + C(2f)+ C(3f)... where each C(f) is the part of the original pulse diveded with the Fourier Transformer, with the formula (*) value for every frequency, with angle a(f), a(2f), a(3f).. ?

This answer could be important to understand if the pulse is not sinusoidal how can I decide the couple.

If everyone knows ideas, could be sended to l.carlino@rfi.it

Thanks — Preceding unsigned comment added by 217.222.110.44 (talk • contribs) 30 March 2005 (UTC)

General
The description of the Italian railway relay above sounds like an AC Vane Relay.

These relays are used on electrified railways to detect the presence of trains and operated the signals. Because the power of the traction (1 MW) is so much greater than the power of the track circuit ( 1W ), special precautions must be taken to prevent the traction current swamping the track circuit current leading to a false green. In the AC Vane relay, the track circuit current at the relay has to be in the right phase compared to a reference current, and this provides the necessary immunity.

AC Vane relays are however fairly insensitive, and require undesirable insulared blockjoints and are being replaced by more modern electronic relays, some of which are jointless, such as the CSEE track circuit. — Preceding unsigned comment added by Tabletop (talk • contribs) 27 October 2006 (UTC)

SPDT, DPDT, ETC
Information should be added to the "Relay" article defining the meaning of "poles" and "throws" such as SPDT and DPDT. I would attempt to add it myself but I am fuzzy on it myself.
 * Added the information. Please see if its ok. Rohitbd 12:59, 1 March 2006 (UTC)

The switching information gets lost in the "Types of relay" section and ends up looking like it is a continuation of the types. Should it be broken out into another heading, or just better distinguished and stay here? Regardless, I think it needs something to keep it from being lost in the clutter. --Stangbat 18:33, 8 December 2006 (UTC

Irrelvant Entry
I removed "reed switch" but left reed relay. A reed switch that can detect the presence of a magnet is a sensor Commonly used in security systems to tell if a window has been opened. I also removed "vibrator". It doesn't relay a signal, it generates one. Once common in mobile radios. Bell was also removed.Seán 07:54, 12 March 2006 (UTC)

''Relays may also be operated by heat where a coil heats a bi-metal strip to open contacts, or where a solder pot melts, releasing a spring to operate contacts. Such heat-activated relays are commonly used for motor circuit protection.''

THis does not fit with headline defn and is therofore NOT a relay. How can we handle this one without deleting it I wonder. any suggestions??? Light current 22:48, 4 August 2005 (UTC)


 * Move it to sensor or switch, or both? --Heron 21:30, 5 August 2005 (UTC)


 * I have joined it with contactor. Bi-metallic relays were once common for time-delay circuits - another section. Meggar 02:03, 2005 August 6 (UTC)


 * Are you talking about a klixon? 19:04, 2005 October 25 (UTC)


 * I think Meggar is referring to "overloads". In any event, if it's bi-metallic, it's temperature sensitive and not time sensitive which is what's needed for a time delay.Seán 23:46, 5 March 2006 (UTC)


 * Bi-metallic time-delay relays had a heater that warmed up the strip over some time, after which it would open or close. They were common items once. The "overloads" also involve time to match the heating rate of the motor that they protect. Meggar 00:42, 6 March 2006 (UTC)
 * I've never seen one that I can think of. Could you help with an example? All of the overloads I've ever used required me to look at the data plate of the motor and find the FLA (full load amperage) and select the proper heater that will trip at that current. Electric motors have a short period during startup where they draw "inrush current" which can be ten times their rated current. The overloads are designed to ignore this. Seán 01:20, 6 March 2006 (UTC)
 * The "flasher" or "indicator" unit on Cars (Automobiles for those in the US of A!) certainly up to the 1990s if not beyond - they are made to provide a cyclic output by passing the current for the heating element through the Normally Closed contacts - with the intended side-effect that a reduced current (from one or more failed lamps) reduces the heating effect so that the time the contacts are closed (and the working lamps are lit) is longer and conversely the time they are open (and the driven lamps are NOT lit) is significantly reduced; This change in duty-cycle and "flashing rate" is used to indicate a bulb failure...! SlySven (talk) 11:55, 16 January 2016 (UTC)

My apologies - Meggar pointed out an example I hadn't seen since the sixties. I had forgotten thermal time delay Seán 02:02, 6 March 2006 (UTC)

Circuit symbol
The article does not contain the circuit or schematic symbol of a relay. Rohitbd 12:20, 1 March 2006 (UTC)


 * I will try to find one or draw it myself. Be patient, I just started. I have yet to play with the drawing utility Seán 23:46, 5 March 2006 (UTC)

Added the image showing circuit symbols of relays. Please check if it is ok. Rohitbd 12:59, 1 March 2006 (UTC)


 * It does indeed show the relationship of SPDT as compared to DPDT, however, a relay is usually depicted in the relaxed position. Seán 23:46, 5 March 2006 (UTC)
 * Hmm...although I am not sure what a "relaxed position" means...perhaps you could make that change...? If it is any help, I have used MS-Paintbrush to create the image. Rohitbd 11:20, 6 March 2006 (UTC)
 * The relaxed position is where the contacts would be if the coil is not enegized. In the case of DPDT (double pole - double throw) the NC (normally closed) contacts would be closed. The contacts in the picture are shown midway between energized and relaxed. In a high current application this would cause a lot of arcing. I just printed out the page on how to upload graphic files. Seán 00:20, 8 March 2006 (UTC)
 * Changed the image to reflect the relaxed position. Please see if it is ok. Also, please sign your posts with ~ . Rohitbd 19:38, 7 March 2006 (UTC)
 * There is a drawing somewhere on the relay itself. [] Seán 00:30, 8 March 2006 (UTC)
 * Notice how terminal 5 (common) is shown connected to terminal 1? This is the circuit when the coil is de-energized or relaxed. When the coil is energized or activated, terminal 5 will be connected to terminal 3. The coil is drawn as a zig-zag line. The symbol is similar to the symbol for a resistor. The drawing is simply trying to show a fixed load. The current draw of the coil is consistant no matter what current the contacts are carrying. Also notice how the coil is shown as a separate circuit? This is electrical isolation.Seán 03:01, 8 March 2006 (UTC)

Time Delay
Time delay is mentioned at least twice is this article. There are time delay devices attached to relays. There is "delay on" where the coil is energized and some mechanism holds the contacts completely open for a set time. After the set time, the mechanism lets go of the contacts and the magnetic force of the coil quickly takes the contacts from all the way open to all the way closed. In the delay off style, the coil is relaxed and some mechanism holds the contacts all the way closed for a set time. After the set time, the mechanism lets go of the contacts and the force of the spring carries the contacts from all the way closed to all the way open quickly. There are several different mechanisms. There are clocks and electric motors and dashpots which are small pistons that release fluid slowly. All of them incorporate a trigger that releases the contacts quickly. All of them are time sensitive not temperature sensitive. The copper disc is used on the solenoid/armature of an AC coil. AC current would relax its hold on the contacts 120 times a second as the alternating current passed through zero. The copper disk prevents that. Seán 00:58, 6 March 2006 (UTC)


 * Thermal time-delay relay
 * Yes the copper disk used on all AC relay coils to prevent buzzing, fits around part of the coil to delay the phase of the field and prevent zero flux trouble. There is also a DC dropout time delay done with a copper disk around the entire coil as described in the article. Meggar 01:13, 6 March 2006 (UTC)

Latching relays
Someone needs to do a better job of describing latching relays, especially the simple latching relays that factory machines use (with green start buttons that are recessed and red stop buttons that have to be pulled out to allow restart). Anthony717 23:10, 28 April 2006 (UTC)

What does it mean by "two darned relaxed states"?--24.57.106.78 (talk) 00:21, 7 December 2007 (UTC)

Images
Not that you need it, but here's another image. Fit it in if you want. — Omegatron 06:54, 10 June 2006 (UTC)

Unusual relay
Is there any major application for an unusual thermal (not bimetallic) relay with these properties: High current/low voltage (output) huge operating temperature range (0K - 700K or so; theoretically as high as 2500K with the right materials) operates better the smaller it is; power used is proportional to the cube of its size. Theoretically would use less power than a transistor if you made it with transistor-scale dimensions. As a macroscale device (millimeters across) uses milliwatts of power to switch and stay switched. requires precision manufacturing and/or assembly to .03% of one dimension on a relative scale between two parts. They can both be a little big, or both be a little small, but in the same proportion to .03% of that dimension.Cuberoot31 21:57, 26 October 2006 (UTC)

Transatlantic cable
Can this entry be clarified? Does it really even belong here? From reading the entry on the Transatlantic Cable page I can figure out where the author was headed, but without further explanation, this entry really makes no sense. --Stangbat 20:23, 27 October 2006 (UTC)


 * You're right, thank you. This very interesting receiver is basically a galvanometer; not a relay at all.  I have moved the relevant portion to the speed section of the atlantic cable article (without leaving a link) and deleted portions that would be redundant there.


 * This article also has an excessively long lead. The material about contact types would fit better in one of the sections.
 * Jim.henderson 18:03, 8 November 2006 (UTC)

Anybody help me with some info on timing relays? like the basics, would be helpfull. thanks. —Preceding unsigned comment added by 217.34.40.93 (talk • contribs)

Noise
You say Contactor relays can be extremely loud to operate, making them unfit for use where noise is a chief concern.

but you don't say if you are referring to the constant buzzing, or the kerchunk upon closing and opening of the circuit. Also see Talk:Contactor. Jidanni (talk) 01:19, 28 February 2008 (UTC)

Symbols
What about a gallery of different symbols to denote relays and their contacts? Tabletop (talk) 09:36, 2 April 2009 (UTC)

Fuel pump relay in the CAR
I have seen these autoelectricians normally removing the relays if there is a problem and making the direct connections. They say it can work without a relay. No problem. As I am not a engineer, I do not understand the consequences of this. Is it safe? —Preceding unsigned comment added by 196.207.47.60 (talk) 17:46, 20 April 2009 (UTC)

Protective Relays
I think that it should be noted that protective relays are classically electromechanical, but more recently are microprocessor based. They compare digital values as opposed to analog current values. 205.162.225.4 (talk) 20:31, 14 May 2009 (UTC)kyle

Relay suppresion
To reduce arcing between the contacts, you can put a resistor in series with a capacitor across the contacts to reduce the arcing. I've used it quite a few times, but only under instruction.

I've never calculated the values myself. It would be good to include the equations to calculate the values of R and C for a given contact rating and voltage. —Preceding unsigned comment added by Wouse101 (talk • contribs) 09:06, 22 June 2009 (UTC)

reverse voltage in normal relay
hi, i want to know what will happen if u change the voltage accross the DC relay. weather the relay is having permenent magent inside the relay as a moving part. —Preceding unsigned comment added by 123.236.220.190 (talk) 11:47, 18 October 2009 (UTC)

what is relay and how it can be used in simple way and for domestic use  —Preceding unsigned comment added by 122.164.28.201 (talk) 08:58, 14 December 2009 (UTC)

Glossary of terms used to describe relays on data sheets
I would really like to see definitions of terms used to describe relays. Of particular interest to me are the terms non-zero, zero, and random used to describe solid state relays (and possibly others). 70.127.202.34 (talk) 12:35, 2 July 2010 (UTC) Bill

Hans Sauer
Who knows more about Hans Sauer, the inventor of miniature high power relays with 309 patents worldwide? http://de.wikipedia.org/wiki/Hans_Sauer_(Erfinder) --Hyperboreer 18:07, 15 August 2010 (UTC) —Preceding unsigned comment added by Hyperboreer (talk • contribs)

Make it blue!
instead using a semiconductor device to perform switching. I'm not sure how to do it I do not play in the sand box enough, however I suggest making semiconductor a link to the semiconductor page. —Preceding unsigned comment added by 149.152.34.59 (talk) 18:48, 13 November 2010 (UTC)

Perhaps add in : Mercury relay, Coaxial relay, Optical relay
There is a page Mercury relay that could be used to add in a new type easily.

Ther are a large range of coaxial relays used in RF and similar applications that have some interesting characteristics that make them unique. They are designed to have better transmission line characteristics to minimise impedance mismatches.

There are relays that use fibre bending, micro mirrors and perhaps even accousto Optics (if the last is a new idea it is now public domain) to route optical signals from one oprical fibre to another, not sure if these should be mentioned in this article.

Idyllic press (talk) 12:32, 15 March 2013 (UTC)

On reflection I would say Optical relay does not belong here. It is an optical routing device that is controlled by electricity and not by light, where as a relay is intended to amplify or invert a signal of the same type.

Undersea cable amplifiers are sometimes called relays but they are more properly a repeater as they provide more than a simple function. By the same token the thermal relays are valid if they use a heating coil to deflect the bimetallic strip and if they are resetting and not of a fusing type. A more elaborate temperature detection system that has remote sensing is not formally a relay but may often be called a motor starting relay as it usually incorporates the contactor and may have other over load protection though technically it is a 'motor starter' that incorporates a relay etc.

Idyllic press (talk) 11:49, 3 June 2013 (UTC)

using relays in place of plc's? (197.88.31.224 (talk) 09:16, 23 April 2015 (UTC))
i would like to get some advise on weather one would be able to use relays instead of a plc?
 * WP isn't the place for advice, but some of the links can be useful. The PLC article might give you a better start.
 * PLCs began as a substitute for relay-based ladder logic controllers. So for small PLCs, there's still overlap with relays. If you understand ladder logic, you can convert the programming from one to the other.
 * That said, I wouldn't convert a PLC to relays. You can do a lot of programming in a very small, very cheap PLC. With relays, that would cost far more. So for something needing only a few relays, this might be workable. Otherwise the PLC keeps the advantage. Building relay systems, changing them and future maintenance is also more awkward.
 * If you need reliable future maintenance, then relays might have an advantage. Especially if you have a simple problem with lots of outputs, rather than a complicated problem with only a few. Andy Dingley (talk) 09:26, 23 April 2015 (UTC)

Error: Basic design and operation
Existing text: "When the coil is energized with direct current, a diode is often placed across the coil to dissipate the energy from the collapsing magnetic field at deactivation, which would otherwise generate a voltage spike dangerous to semiconductor circuit components. Some automotive relays include a diode inside the relay case. Alternatively, a contact protection network consisting of a capacitor and resistor in series (snubber circuit) may absorb the surge."

Contrary to the existing wording, the snubber network is not an alternative to the diode across the coil. These deal with two separate issues in two separate parts of the circuit.Gwideman (talk) 07:04, 13 July 2015 (UTC)
 * Yes, I don't think I've ever seen an RC snubber across a coil anyway (they're placed across the contacts). Andy Dingley (talk) 08:16, 13 July 2015 (UTC)


 * I'm not so sure about there being a significant difference. I think engineers may distinguish different applications of the technology, but they do the same thing.
 * The snubber network across some mechanical contacts tries to prolong the life of the switching contacts by either suppressing glow and arc discharges/breakdowns or by limiting their duration. The problem is some stored energy in an inductive load, and that energy is dissipated in snubber network.
 * The catch diode across a solenoid tries to prolong the life of the switching transistor by preventing destructive breakdown. The energy is dissipated in the diode. I have seen applications where a resistor is put in series with the diode. The decay time constant is L/R, and with just a diode the value of R may be too small. If the solenoid/relay/inductor/whatever needs to release/deenergize quickly, R needs to be increased. Adding a series resistor increases the voltage across the transistor but reduces the decay time. (A series Zener could also be used to dissipate the energy.)
 * Topologically, if you believe the powersupply is a perfect short and ignore the DC bias issues, then placing an RC network across a coil is similar to placing it across the switch contacts. Likewise, placing the catch diode across the coil is similar to placing it across the switching transistor. And if you use an RCD network, then the DC bias issue goes away and the power supply can look like part of the capacitor.
 * Presumably, one can transfer the solenoid energy to a capacitor and slowly discharge it through a resistor. Like Andy Dingley, I have not seen a circuit where that is done, but that does not mean it hasn't been done. (A couple years ago a friend described a protection network for a switching power supply that used a 0.1 W dissipation resistor when the resistor dissipated 15 W; the resistor would burnout in a few hundred ms. I don't recall if a capacitor was involved.) I have seen switching power supply designs that employ a clamp winding and clamp diode that return the transformer's magnetizing energy to the switching power supply's storage capacitor.
 * Glrx (talk) 14:53, 17 July 2015 (UTC)
 * Both systems are there to control spikes from reactive loads. The difference is the impedance: in the relay coil, this is a high impedance circuit and so a high voltage at a low current. A forward-biased diode is appropriate, to protect the reverse-biased transistor. In the switched circuit, the current may be large (this is presumably why a relay was needed in the first place) and the impedance is low. The current would be excessive for any diode-based solution (and the direction may not be predictable, making a diode unworkable) and so a capacitor is used instead. If the current is really quite large, a series resistor is needed with the capacitor. Andy Dingley (talk) 15:27, 17 July 2015 (UTC)

Contact Materials
I am aware that different material are/have been used to form the contact surfaces of relays, including gold for low voltage/low current applications and some silver compounds for others - the latter having the undesirable side-effect of degrading if not enough current is passed through them. Can anyone provide more information on this? There is a little coverage for the specialised mercury-wetted case but what about others? SlySven (talk) 12:27, 16 January 2016 (UTC)


 * Just because somebody asks for something to be added doesn't mean you can ignore the verifiability policy. Every Wikipedia editing webpage clearly states, "Encyclopedic content must be verifiable." Please supply references before reintroducing this content again, per WP:BURDEN. I tagged this article Refimprove in 2009, and ever since then you have been adding uncited content—completely ignoring both the tag and the policy. You have been rude to me on this and other articles, reverting my maintenance tags with the unjustified excuse of "drive-by tagging", and reverting my efforts to minimize uncited claims. You have even called me incompetent, yet I am not the one ignoring policy. Clearly, you do not like these polices, and do not believe they apply to you (i.e. you are special). If your personal beef with our policies continues, I will have to report the issue to ANI. – void  xor  19:10, 7 January 2018 (UTC)
 * Or, we could grow the encyclopedia and identify that the paragraph needs a citation. Could we maybe find references instead of tagging? Or cutting out scary paragraphs that might frighten people who feel insecure if there isn't a little blue number following every sentence? --Wtshymanski (talk) 19:23, 7 January 2018 (UTC)
 * Exactly what part of WP:BURDEN don't you understand? The burden is on you to supply references at the time that you add content. The Citation needed tag is meant to mark existing uncited content, not as a way to circumvent verifiability policy. – void  xor  19:34, 7 January 2018 (UTC)
 * You know, without a threshold level of competence assumed in every editor, this whole system falls apart? Do we still have that essay about not needing to cite that the sky is blue? --Wtshymanski (talk) 20:00, 7 January 2018 (UTC)
 * You mean WP:BLUE? It is an essay not a policy. See also WP:NOTBLUE which says pretty well the exact opposite, but that is also an essay and not policy.  What is policy is WP:BURDEN. The burden is on any editor adding material to Wikipedia or re-adding material deleted as unreferenced to provide the required references in support of that material. Simply restoring the content without providing the supporting references is disruptive editing no matter how obvious you regard the content to be. — Preceding unsigned comment added by 86.149.141.199 (talk) 17:12, 8 January 2018 (UTC)
 * Agreed. The contempt, such as in, is unnecessary. And I really don't get "the sky is blue" argument; anybody who thinks that three-phase power is as universally understood as the as the sky color needs to get out more often. – void  xor  01:52, 26 January 2018 (UTC)

Potential Relays missing.
Plenty of sources online, if you google it. Surprised it's not here, given they are used on motors and compressors. — Preceding unsigned comment added by 175gw (talk • contribs) 15:23, 12 June 2020 (UTC)

Another use case?
Uses described in the lead are about one circuit controlling another. It seems obvious to me that it could just as well be a single circuit controlling itself.

Simple on/off switching is perhaps a typical example. It's very simple to implement on/off buttons with a relay. It is also a way in which an electronic device can power itself on and off. OK, so strictly speaking something can't power itself on, but I can imagine a device having a standby subcircuit for this.

Is this a use relays are put to to any significant extent? Or is there another method that is typically used for on/off switching of these kinds? — Smjg (talk) 16:40, 20 August 2023 (UTC)