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Anonymous Poster

Regarding Latching Relay

12/16/2007 11:19 PM

Hi friends

Can any one help me in accessing the details in depth from basic concepts about latching relay.

pls suggest me which websites will be more useful ??

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#1

Re: Regarding Latching Relay

12/17/2007 12:11 AM

The basic definition is that a latching relay maintains state in the absence of a control signal. From what level of knowledge are you operating with? I don't want to waste both of our time explaining something far too basic or far too advanced to be of use.

Have you tried Wiki or even just a basic Google search? If you have, what specific questions do you have after reading what you found there? If you have not even tried that much, at least go to that much effort to educate yourself and then come back with some specific questions. Good luck!

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#8
In reply to #1

Re: Regarding Latching Relay

12/18/2007 8:51 AM

You touched the heart of a CR4 problem.

For some mysterious ( laziness?)reason many of the posters prefer to throw in a stupid question instead of say Googling it first, or investigate to some degree. "Latching Relay" brought me over 80.000 answers, Wiki included. in less than 0.18 of a second.

Just as you say we should ignore these posts, not waste our time on kindergarten level education. After all the title is "The engineer's place for news and discussion..."

Wangito.

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#2

Re: Regarding Latching Relay

12/17/2007 3:53 AM

A latching relay can be wired from a normal relay. One of its normally-open contacts is wired in parallel across the exterior contact that energises the relay. Once the exterior contact closes, the relay energises and closes its own contact, which maintains the supply to the relay once the exterior contact is opened again. Such a relay requires a separate exterior contact in order to de-energise.

Rather than an internet search, an hour or so with a 9V battery, some wires and a miniature DC relay may prove of more benefit - try and make one!

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#9
In reply to #2

Re: Regarding Latching Relay

12/18/2007 9:03 AM

Hey there PW,

I must disagree with you.

What you describe is a Self holding arrangement. A latching relay will hold it's switching mechanism open or closed mechanically by mean of a Latch, (spring return) hence the name, or a balanced spring, without the presence of energizing power. It will only require a short pulse of power to close, and another to open.

Wangito.

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#13
In reply to #9

Re: Regarding Latching Relay

12/20/2007 4:27 AM

(No problem with constructive disagreement.)

Then what is needed is the same sort of relay that can be found in vehicle headlight dip circuits. Make the circuit once, and the switch changes state. Make it a second time and the switch changes back again. Specialist automotive parts stores are the sort of places to find such a thing off-the-shelf, and it won't break the bank.

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#14
In reply to #13

Re: Regarding Latching Relay

12/20/2007 6:25 AM

OK,

They AKA "Bi-stable relay"

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#3

Re: Regarding Latching Relay

12/17/2007 10:52 PM

A Simple 1n4004 type diode will make it easier if using normal 12v spdt type relay.

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#4

Re: Regarding Latching Relay

12/17/2007 11:29 PM

A latching relay needs a voltage pulse to make or break contacts points. It then stays in that latched position until an unlatching event occurs, another pulse.

There are a few ways to do it, look here.

http://www.google.com/search?hl=en&q=%22latching+relay%22+%2Bways&btnG=Google+Search

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#5

Re: Regarding Latching Relay

12/18/2007 3:10 AM

I've been using latching relay for years to control water pumps whenever I install 2 pumps ( 1 duty 1 standby ) it is just like a flip flop relay and close one of the 2 contact at one time and changes the contact everytime it is being energised.

Don't know whether this will help to answer your question, but I'll try to pass you more info when I get hold of them.

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#6

Re: Regarding Latching Relay

12/18/2007 3:15 AM

You can try to check from the websites below,

http://www.ia.omron.com

http://www.galco.com

Hopes it will help you to solve your problem.

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#11
In reply to #6

Re: Regarding Latching Relay

12/18/2007 1:25 PM

Hello William,

Thanks for your kind words of encouragement. It is always good to know that someone appreciates your efforts.

Wangito.

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#7

Re: Regarding Latching Relay

12/18/2007 4:02 AM

The direct-on-line motor starter is a circuit built as a latching relay with a start pushbutton and a stop pushbutton. Take a look at a wiring diagram for a small starter.

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#10

Re: Regarding Latching Relay

12/18/2007 10:53 AM

The question is "which websites will be more useful." I think hat has already been answered. That would be search engine websites such as Google, Ask.com, etc...

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#12

Re: Regarding Latching Relay

12/18/2007 6:41 PM

Basically, latching relays are electromechanical devices that latch-on to a different state everytime they are pulsed with a same signal source. The mechanism that latches is usually a plastic guideway and a stiff lever that toggles in one direction, and on the subsequent signal pulse it latches to the other. You see these on automatic gates and doors. They are beneficial for manufacturers and consumers because they usually cut down on cost by not having to make duplicate or complicated circuits; (ie. 2 relays for opposite similar operation).

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#15

Re: Regarding Latching Relay

12/22/2007 2:57 PM

Permanent magnet or Electromagnets are used in latching Relay to hold in one or the other side.

The 1st latching-ON-OFF-device I used was an ON-OFF switch for Bath-Room [Wash-Room] to avoid electric shock in Wet Area. Ratchet operated by a Silk-Cord hanging down to user's approach while switch fixed above near ceiling of roof.

The 1st Latching-Relay I came across was based on above switch idea.
A Ratchet-operated relay; ratchet pushed to next step by an electric plunger.

Later developments brought Centre-balanced moving contact moved by electric-coil(s) came up using Magnetic-Catch.

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Users who posted comments:

Anonymous Poster (1); aurizon (1); CSM Engineer (1); Haajee (1); PWSlack (3); ronald (1); Self Thinker (1); wangito (4); William Tan (2)

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