Unlatching a Latching Relay

Electromechanical Relays
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1

What kinds of latching relays are there and how do you unlatch them?

2

There are two main types of latching relays - single coil and dual coil.

Single Coil Relay
Supply the relay with the rated coil voltage to latch, this can be steady or a single pulse. The datasheet should show the minimum amount of time the voltage is needed to activate the relay (usually in the milliseconds). The coil will stay latched after the voltage is removed. To unlatch the relay, another steady or pulsed voltage must be supplied to the coil in the opposite direction or polarity.

Dual Coil
Dual coil relays have two coils. Supplying the first relay coil with the rated coil voltage (again this can be steady or a single pulse) will latch the relay. The coil will stay latched after the voltage is removed. Supplying a voltage to the same coil again will not affect the relay. To unlatch the relay, voltage must be supplied to the second coil.

3

Thanks Joey,

Is there some sort of a pulsing relay that one could use to pull and push the arm on this solenoid?
https://www.digikey.com/product-detail/en/delta-electronics/DSML-1153-12P/1144-1412-ND/6618793
The controller that I am using turns on 12vdc when the temperature is right and turns it off when the temperature is not right. What should I use to control the solenoid?

Thanks again…

4

Hi StillnessSpeaks,

Although there could be many options that you could use, I would look into our Temperature Controllers.

These are able to monitor temperature through either a thermalcouple or other type of temperature sensors and control the output via a relay.

Here is a list that I have narrowed down a little bit https://www.digikey.com/short/pnzvzj

If you have any questions on these devices, please let us know.

5

Hello Travis,

Thank you for the help. I actually already have a controller that is measuring both the temperature and the humidity. When those 2 are correct the controller outputs 12v dc. When those are incorrect the controller stops outputting 12v dc. The solenoid that I have chosen requires pulse. Would you please recommend something that would somehow create a pulse everytime my controller changes state?

Thanks again Travis. You guys are amazing…

6

A few things of note: first, folks that haven’t read this other post will be missing some important context regarding the project at hand; it’s helpful to keep related inquiries in a single thread, so that sort of connection doesn’t get lost over time.

Second, there’s no “push” to be had here; the solenoid mentioned will provide a retractile force when power is applied, with extension of the plunger achieved using spring tension, gravity, or some other such external force when power is removed.

Last, it appears that there may be a misapprehension of the duty cycle spec occurring here; the part number mentioned is designed to be operated for 0.1 second or less at a time, a maximum of once per second. The force exerted by the solenoid persists only so long as power is applied, which would not appear appropriate for a louver/vent control application without provision of some sort of external mechanical latching mechanism.

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The simpler approach to the task at hand would appear to be using the -12C variant of the solenoid (DK P/N 1144-1410-ND) which is suitable for continuous operation, to either open or close the louver with the return operation achieved by spring, gravity, etc. The 12V control signal could then be used directly if it is capable of delivering the required current and adequately protected, or perhaps used with an intermediate relay if it is not.

1 Like
7

Hi Rick,

Thanks for the help and thanks to all of you who have guided me through this process.

I unfortunately do have a couple of more questions if you will please bear with me.

The DSML-1153-12C would make my life much easier and the controller can handle the load more than likely even with the total load of 7 solenoids energizing at the same time. I will double check the specs on the controller but it is rated to operate several 10-watt muffin fans.

The total load with 7 - solenoids will be 49 - watts which may be running a total of 12 - hours per day times 30 - days per month at 8 cents per kilowatt hour will cost $1.41 per month to operate which is excellent.

The solenoids may be cycling on 20 - times per day times 365 - days which is 7,300 cycles per year which is also excellent.

I believe that the only questions are when the solenoid is in the off state how much physical pressure does it take to pull it down say if I were to press down on the shaft?
Likewise when the solenoid is in the on state how much physical pressure does it take to pull it up say if I were to pull on the shaft?

Thanks again…

8

There’s a chart on the datasheet that describes the force applied by the solenoid with rated input as a function of travel distance from the fully-retracted state. The further extended the plunger, the lesser the force it can apply. The external force required to extend the plunger would be approximately the weight of the plunger itself.

9

Thanks for the help Rick,

Having trouble grasping about how much force that is in laymans terms.
Do you think a person would be able to push shaft down with his finger? Can you possibly compare that amount of force to an everyday force?
Likewise do you think a person would be able to pull shaft up with his hand? Can you possibly compare that amount of force to an everyday force as well?

Thanks again