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Resetting Latching Relay with Momentary Button

wowblaauw

Jul 22, 2023
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All, being a complete newbie and not studied electronics for some 40 odd years since age 11, I come to this forum for help.
I have a project which requires as in the title a latching momentary relay with button - this requires a momentary button to be pressed which cuts power to the device and on cutting power to the relay resets the relay - make sense? Please let me know what you know, is there such a thing?
Thanks in advance
Craig
 

crutschow

May 7, 2021
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have a project which requires as in the title a latching momentary relay with button - - this requires a momentary button to be pressed which cuts power to the device and on cutting power to the relay resets the relay
Not enough info.
How is the relay set?
What is the relay contact load voltage and voltage, and AC or DC?
What is relay coil voltage, and AC or DC?
 

Alec_t

Jul 7, 2015
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What type of latching relay? One with two coils (one for Set and the other for Reset) or one with a single coil (energised with one polarity current for Set and the opposite polarity for Reset)?
 

Delta Prime

Jul 29, 2020
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Yes more information. Is it a bi directional relay that latches is it magnetically or physically locking .The term latching implies memory, magnetic latching relays are held in place by electromagnetic forces, whereas a mechanical latching relay is held in place by a physical locking mechanism. They come in many flavors depending on your application ask for it by name. Specifications please....
 

AnalogKid

Jun 10, 2015
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Depends on the relay. Part number / coil voltage / coil current / coil power - anything - ?

Also, what contact arrangement do you need for whatever is being controlled?

The basic idea is that the relay needs an extra set of contacts beyond what is needed for the task. For example, if you need DPDT contacts for the task, then you need a 3 pole relay. The extra pole forms the latch circuit.

For the complete details, we need to know more about what power source and circuit or button arrangement is controlling the relay to set the latch.

ak
 

wowblaauw

Jul 22, 2023
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Hi, I heres an attached drawing which matches my requirement:
I hope this makes sense; basically I require the 12v utilising 0.3a/h device to power from a vehicle ignition switch at 12v but to allow the user to switch off by pressing a momentary button. When the ignition switch is then turned off, effectively resets the latching relay and resets it. When the ignition is then turned on again it turns on the device.
 

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  • Latching Relay Switch.png
    Latching Relay Switch.png
    34 KB · Views: 9

crutschow

May 7, 2021
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Below is the LTspice simulation of a circuit, that should do what you want:
It uses a MOSFET (M1) to power the relay coil from the R2-C1 momentarily gate signal when the +12V is applied (blue trace) until the relay pulls in and is latched by the ground connection through one of the relay's NO contacts and the NC momentary push-button, S1 (green trace).
Opening S1 (red trace) turns off the relay and load (purple trace), which is then ready for the next turn off and on of the +12V supply.

1690139491418.png
 
Last edited:

wowblaauw

Jul 22, 2023
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Below is the LTspice simulation of a circuit, that should do what you want:
It uses a MOSFET (M1) to power the relay coil from the R2-C1 momentarily gate signal when the +12V is applied (blue trace) until the relay pulls in and is latched by the ground connection through one of the relay's NO contacts and the NC momentary push-button, S1 (green trace).
Opening S1 (red trace) turns off the relay and load (purple trace), which is then ready for the next turn off and on of the +12V supply.

View attachment 59981
Although I was rather hoping for something simpler, I suppose my next question is where i can get these mass produced?
 

crutschow

May 7, 2021
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my next question is where i can get these mass produced?
Didn't know this was for production, as my circuit was not particularly designed for minimum production cost
The relay is a significant cost and will depend upon the load.
Does it have to be a relay controlling the load?
How many do you expect to sell?
 

wowblaauw

Jul 22, 2023
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Didn't know this was for production, as my circuit was not particularly designed for minimum production cost
The relay is a significant cost and will depend upon the load.
Does it have to be a relay controlling the load?
How many do you expect to sell?
Probably looking at a minimum of around 1,000 to start maybe leading up to many 000's thereafter - this is part of a project which has been constantly changing for many years and is finally in its last stages pre-sale.
 

wowblaauw

Jul 22, 2023
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I just found what I have been looking for - do you think that this is relevant to what I am looking for?
 

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  • Latching relay with reset button Image - 1.jpeg
    Latching relay with reset button Image - 1.jpeg
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AnalogKid

Jun 10, 2015
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What post #15 shows is that the controlling circuit (the relay and switches) and the load that is being controlled (shown as an LED) both run on the same power source. If you had told us this in post #1, this thread would have been finished in post #2.

Shawn19 is running a similar thread at All About Circuits.

ak
 

wowblaauw

Jul 22, 2023
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I did say that I was completely new to this process and thank you very much for your update
 

crutschow

May 7, 2021
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I just found what I have been looking for - do you think that this is relevant to what I am looking for?
Not really.
If you answer our questions and tell us exactly what you want to power with this circuit, then we can better suggest a circuit for your needs.
 

Harald Kapp

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What aboutthis circuit?
1690268690560.png
solenoid = relay coil
 
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