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I am looking at latch pull solenoid DSML-1153-24C. I have the following questions:
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?
What the S and F terminals of the solenoid denote?
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.
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.
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?
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:
“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.
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?
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?
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.
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.
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.
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?
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.