Solenoid DSML-1153-24C

I am looking at latch pull solenoid DSML-1153-24C. I have the following questions:

  1. Regarding the stroke length of 19.05mm for this solenoid, is that the total length of the stroke or just the part that extends out of the frame? If it is the total length, may I know what the length of the part that extends out from the frame is?
  2. What the S and F terminals of the solenoid denote?
  3. What is the inrush current of the solenoid? It is not indicated in the datasheet, is there a rule of thumb to estimate such as 3 or 4 times?

I need this urgently, appreciate if anyone can help. Thank you

Thank you for your inquiry and welcome to the community.

It’s going to be the total length of the stroke.

Based on the drawing fully extended measuring from the face of the solenoid, the pin position will extend to 1.074 inches and the tip of the actuator would extend 1.23 inches.

On your other two questions I’ve requested further support, we’ll get back as soon as we have any information.

Hello @hipoweredge,

Thank you @Kristof_2649.

I’m unable to locate a reliable source for the S and F designations. I have two possible interpretations:

  • S could stand for skinny referring to the terminal blade thickness. This assumes the DC solenoid does not have a polarity.

  • S could also stand for source (positive). This assumes that the coil requires proper (absolute) polarity as described in this related article. Given the picture, I believe this is unlikely. However, it would take seconds to determine once the relay was in your hand as it would work with one polarity and not the other.

As for inrush current: the coil inductance is the dominating factor. The current will be slow to rise and slow to dissipate. Consequently, there will be no surge. You may be interested in this article which shows the turn on and turn off current for a large contactor.

Please let us know if this solved your questions.

Best wishes,

APDahlen

P.S. You may or may not require a diode or TVS diode to catch the flyback voltage spike when the solenoid is turned off.

1 Like

Sorry, I am a bit confused here. The drawing shows the solenoid in the energized condition, right? Could you please explain how you interpret the length of the stroke in the de-energized condition? Also, what do you mean by the pin position here?

Here is the response from the Product Specialist-

The S and F means start and finish of the windings.

Got confirmation that the inrush current is the current limit for each solenoids, therefore, the inrush current for DSML-1153-24C is 0.3A.

2 Likes

Hi hipoweredge,

After looking at the documentation, and considering that the table lists the maximum stroke length as 0.75 inches, I would interpret the dimensions as follows:

Approximate lengths:

  • Energized state = 1.24" + 1.22" + 0.156" = 2.62 inches
  • De-energized state = 1.24" + 1.22" + 0.156" +0.75" = 3.37 inches

“Pin position” (the hole in the actuator) is 0.156 inches from end of actuator.

I don’t know the literal meaning of “S” and “F”, but standard latching solenoids have two contacts. When current is passed in one direction, it energizes the solenoid, and when current is reversed, the solenoid is de-energized. I would guess that “S” would be the positive terminal to energize it, but this is simple to verify once you receive the part.

1 Like

Thank you, Jeff

1 Like

Thank David

1 Like

Hi David, I received the solenoid today. I am wondering if I misunderstood the meaning of a pull-latch solenoid. The solenoid arrived with the plunger inside, but since it’s in a de-energized state, shouldn’t the plunger be extended outward in its current state?

Hello hipoweredge,

The datasheet for this part does say that it supposed to retract when energized. This may have been energized and a pin put in to keep the spring retracted during shipment. Is there a pin/ring you can pull out and see if the spring extends?

Regards,
Klint

Hi Klint,

I was suspecting the same thing, but I do not see any part that holding the plunger in. You can see in the pictures below from different angles. Appreciate if you can help to point out how to solve this. Thank you.





Hello @hipoweredge,

Intriguing component.

With your pictures, we can clearly see the permanent magnetics that hold the plunger in position.

I have requested a part from DigiKey stock. I’ll post an article as soon as I can.

Sincerely,

Aaron

1 Like

Hi @APDahlen , appreciate if you could get back to me as soon as possible. This part needs to be installed urgently. Thank you for your help!

1 Like

Hello @hipoweredge,

Apologies for tripping on my own feet with this product (DSML-1153-24C).

The black components in the upper section are permanent magnets. The S and F terminals are polarity dependent.

The device has several states:

  • Deenergized:

    • the plunger is held extended by spring tension
    • the plunger will be held closed (latched) if it is physically moved pushed into the core
  • Energized with polarity of coil magnetic field adding to permanent magnet field

    • the plunger will be forcefully pulled into the core and held firmly in position
  • Energized with polarity where the coils magnetic field opposes the permanent magnetic field

    • (dynamic) Upon activation, the plunger is released (unlatched). Spring tension will extend the plunger.
    • (steady state) Once activated, the plunger will behave as if unenergized albeit with less force. The plunger will latch if it is mechanically forced.

Summary: The plunger is latched into position mechanically or by application of 24 VDC (positive to wide blade). The plunger is unlatched upon initial application of 24 VDC (positive to skinny blade). If the spring tension is insufficient or the load excessive, the plunger will remain in the latched position.

Tech Tip: This is a pull solenoid. The latch release mechanism (plunger push out) is passive. It’s also momentary. If the plunger is not immediately withdrawn upon application of power, it will remain latched. Consequently, this solenoid and associated spring have limited ability to push against a load. You may need to add additional mechanical mechanism to ensure the plunger is unlatched.

Power

The solenoid requires circuitry to apply polarity is two different directions.

  • one polarity to forcefully retract (pull) the plunger
  • reverse polarity (pulsed) to release the latch

This could take the form of a pair of relays in a configuration similar to a three-phase reversing motor starter. One relay activates to apply retract power, the other activates to release the latch. The challenge is to include interlock protection so that only one relay activates at any given time.

I’ll present a complete circuit soon.

Please let us know if we can assist.

Sincerely,

Aaron

Hi @APDahlen ,

Thanks for the info. Given that I only have one control switch and expect the solenoid plunger to be pushed out when the switch is open, I’m considering using a relay with NC and NO contacts to change the polarity on the solenoid. I’ve attached a hand sketch—please let me know if you foresee any issues. Additionally, can you confirm that the solenoid can handle 100% duty on both polarities?

Hello @hipoweredge,

Yes, that will work as shown in this video with a few caveats:

  1. The “C” at the end indicates that this is a continuous duty mechanism.

  2. The coil will dissipate 7 W continuously and will be warm too hot to hold.

More to follow as I write the article describing the mechanism.

Sincerely,

Aaron

P.S. Given the “rule of 10” which tells us that life will double for every 10° C reduction, I would recommend a pulsed circuit.

1 Like

Hello @hipoweredge,

Getting closer to writing the article about the solenoid. Today I completed the test platform. I hope to have the article written within the week.

Have a good weekend,

Aaron

Hello @hipoweredge,

The article is complete.

You may be interested in the section of asymmetric magnetic fields toward the end of the note. Assuming your application spends most of the time in the unlatched state, you could benefit from the resistor and diode. This would significantly reduce the coil heating and provide an improved mechanical response.

Sincerely,

Aaron