How Can I Design a Powerful Yet Low-Power Electromagnetic Lock?

[felix_cat]

Well I have got a lot of text warnings. Sorry for my disrespectful attitude Sir.

My request to you is just to look at the following link and explain the structure and design. It would be very thankful,grateful,utmost kind of you.

http://www.sdcsecurity.com/shared/eblast/081507_sdcsecurity/modularkit_datasheet.pdf"

This is the lock. Please explain why has he not coiled the solenoid directly on to the iron core rather he uses some black material. Could you kindly explain what that black material is and why the solenoid is coiled onto that. Give your guess of the dimensions of the core too.

And the reason why quiz questions are irritating is that you reply the answer to them very late. The other person has project deadlines to meet with if you are not aware.

Regards

 

[berkeman]

Well I have got a lot of text warnings. Sorry for my disrespectful attitude Sir.

My request to you is just to look at the following link and explain the structure and design. It would be very thankful,grateful,utmost kind of you.

http://www.sdcsecurity.com/shared/eblast/081507_sdcsecurity/modularkit_datasheet.pdf"

This is the lock. Please explain why has he not coiled the solenoid directly on to the iron core rather he uses some black material. Could you kindly explain what that black material is and why the solenoid is coiled onto that. Give your guess of the dimensions of the core too.

Sorry, I'm not able to understand that pamplet with just a quick look. Maybe others are able to understand it...

 

[felix_cat]

Then do not take a quick look please . this is the forums , you have to help others, give time to them , come on , this is not fair. Berkeman, help please ...
This is a burning issue on forums, not a single forum on the internet deals with designing the electromagnet properly, you have to answer for the sake of science.

 

[Maria2009]

berkman ... I am a newbie . ... let's face it ... i don't have answers to ur so called 'quiz questions', rather dealing me with sarcasm you could have some positive attitude and help me. I am in my 5th semester here, not working for a company like you.
I just asked you to help me make a friggin solenoid. that's it ... and my design won't let anyone lock em self up. YOU can just pull the plug out and the MAGNETISM IS HISTORY ... for godsake ...

and you josh cum here and sayin ... "we got rules mister. no one dies burning in the fire with a faulty design ... we don help peeple make that kinda stuff here" ... WELL for crying out loud I am not making such a thing. Skeptic gave the stupid idea for the PERMANENT magnet design... that's how u make peeple locked in PERMANENTLY... i think i wasted my time coming here on the forums .. buncha fyzists .. buh !

I'm very interested! I would love to find out more inforamtion related to this topic. Thanks in advance.
me too, I need more detailed info

simulation taux banque credit immobilier de France[/color] - Credit immobilier de France, simulation credit immobilier. Résultat mitigé pour le crédit immobilier de France.[/color]simulation taux banque credit immobilier de France[/color]

 

[MATLABdude]

Well I have got a lot of text warnings. Sorry for my disrespectful attitude Sir.

My request to you is just to look at the following link and explain the structure and design. It would be very thankful,grateful,utmost kind of you.

http://www.sdcsecurity.com/shared/eblast/081507_sdcsecurity/modularkit_datasheet.pdf"

This is the lock. Please explain why has he not coiled the solenoid directly on to the iron core rather he uses some black material. Could you kindly explain what that black material is and why the solenoid is coiled onto that. Give your guess of the dimensions of the core too.

And the reason why quiz questions are irritating is that you reply the answer to them very late. The other person has project deadlines to meet with if you are not aware.

Regards

Then do not take a quick look please . this is the forums , you have to help others, give time to them , come on , this is not fair. Berkeman, help please ...
This is a burning issue on forums, not a single forum on the internet deals with designing the electromagnet properly, you have to answer for the sake of science.

We don't give out designs or do your work / homework for you (which seems to be the case here). You might exhort us to spend time and effort upon your behalf (which we do, despite this being 'leisure' or a hobby for all of us) but you'd better do the same. As Jerry Maguire says, "Help us help you!" And in your very first post, you stated explicitly that you didn't want to be spoon fed a solution, you wanted us to do it in such a way(?) that you learned!

Okay, TA in me aside... As a 5th semester student in EE / Electronics Engineering, you should've taken an electromagnetics class. And, as you say, you know that an electromagnet depends upon both the number of turns as well as the current that goes through it:
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/elemag.html

Now, you may or may not know that you can multiply the effect of an electromagnet using a core with high magnetic permeability (yes, there are things that are much better than the iron / steel core):
http://en.wikipedia.org/wiki/Permeability_(electromagnetism)

With these in mind, you should be able to figure out how SDC does it. If you have to design your own system for authentication / control and locking (and it sounds like time's running out), don't do it the most complicated and sophisticated way possible (by designing and building your own electromagnet), do it the easiest, and most probably-successful way of doing it: with an off-the-shelf solenoid that pulls / engages a latch, as others have been suggesting!

Is the point of the course to design / build your own electromagnet which can rival commercial products? No? Then breathe, quit panicking, and figure out what you actually have to do (in the time available to you), and not what you wanted to do at the start of the project. This is what I counsel when the students I TA in my final-year electronics design project start freaking out with a month to go.

 

[felix_cat]

Firstly its a hobby thing.

Secondly, I have got a design, you just do not go by opposing the design and present a whole new mechanism, you provide small alterations to the design. All I wanted was how to construct an electromagnet that could lift 600lbs with 24/12Volts power supply. Building it from scratch was never taught in the course, only numerical questions where you are given the dimensions already, have to calculate the amperes or turns. That is the reason I came to the forums.

Thirdly: I told you guys that I am in a 3rd world/part of the world where research is at the lowest and people making solenoids and coils by just endlessly coiling the iron core. I do not want that, of course that is the difference between an engineer and a technician. That is 6th grade science stuff and has not changed at the College level either, that flux is proportional to permeability, cross sectional area, current and inversely to length. How technically, keeping in mind the changes in permeability as magnetic intensity increases and the magnetic saturation, am I suppose to design it, that was my problem.
Well thanks a lot you guys, certainly, i think i was not even told what was cooking tonight, talk about being spoon fed.
And Maria baby, do not worry. Daddy is going to figure out soon.

 

[MATLABdude]

Well then, that's a good starting point. If you already understand basic electromagnetic theory, and have a design, and you're just looking for some modifications, then go for a core made of permalloy or mu metal, or a laminate electrical steel one.

And now, I'm confused again; if you've got a design, and you understand the theory, and the modifications, then what are you asking of us? How to build this thing for real? You'll need to get a machine shop to build you a core, and to buy yourself some 30 gauge wire. Or, you can go to a motor / coil rewinder (unless you live in a country really, really bereft of infrastructure, like Cambodia, I can almost guarantee you that there'll be quite a few shops that do this) and have them build it to your specifications.

 

[Danger]

This is starting to weird me out big-time.
For safety of yourself and your family, you would want it fail-safe for exit and fail-secure to keep the baddies out if the power fails.
My thought right now (keeping in mind that I've had over a dozen beers) is that you could accomplish both by having the electromagnet mounted on a physically disconnectible mounting bracket. In that case, the permanent magnet on the door would provide fail-secure in a power failure, but you could manually disconnect the electromagnet from the frame if you had to exit in a hurry.

 

[felix_cat]

Thanks a lot guys. That was the support I guess I needed. Well I did all the math, I would post it for maybe anyone of you to check it, the force I calculated was around 4300 Newtons. But I made an assumption of B=1.2T with Ur(mu R) being 3000.

A query if you might help me with, in the textbook, there are numerical questions given where two graphs, one of Relative Permeability(mu R) and second of Flux Density(B) against H(field strength A,turns/meter) are plotted. When the core is tested these results are plotted.

My question is that if I assumed that my core would have Ur 3000 and B=1.2, is it correct ? Should I too first plot a graph and test the core ?
With the calculations I did, I found out that 35 turns on a steel core that is similar to the shape of digit " 8 " (eight) were required, where the coiled wired is on the middle of the digit
Also I assumed that I=0.5A. I guess results are valid ??

-->|(Armature Plate)
=|================<-- Magnetic Core E shaped
=|......=
=|......=
=|......=
=|......=
=|......=
=|......=
=|......=
=|...coiled...=
=|================
=|...here...=
=|......=
=|......=
=|......=
=|......=
=|......=
=|......=
=|......=
=|......=
=|================ <-- Magnetic Core E shaped
-->|(Armature Plate)

looking from side on.

 

[MATLABdude]

35 turns sounds suspiciously low (even though I haven't built one of these before); I think you may be off by an order of magnitude or two. With this whole endeavour, you'll probably need to go through at least two or three iterations (with appropriate analysis in-between) to create something that works to the specs that you're using.

I'm guessing \mu_{R} is \frac{\mu}{\mu0}, however, yes?

Do you have the equipment necessary to determine B vs. H? If not, you're probably stuck with doing some experimentation to try to derive what \mu is under a given set of conditions (and as I say, you're probably not going to build this perfectly first time through).

As Danger and some of the other posters have counseled, I urge you to consider the safety / emergency aspect. Whether it be a big red push button that kills power, or a manual (non-magnetic) unlock bracket that disconnects that frame from the magnet, allowing the (permanent) magnet to swing free with the door, and people to leave if the power fails, or just a big red sign that says "In case of Emergency, PULL POWER CORD TO EXIT!"

This is our duty as engineers: to not just build something, but to also think through failure modes, and ramifications of our design decisions. And what differentiates us from some guy that slaps stuff together without regards to design / thought. I guess we're also responsible when the unexpected happens, or when someone figures out a way around our safety constraints / recommendations, but that's a whole other discussion.

Anyways, good luck with your project, and let us know how it turns out!

 

[felix_cat]

NICE !

One mistake in my previous post by the way, its not a steel core , its an iron core.

Well, got to go to the hardware store now ...

And I would take full notice of safety issues, thanks for reminding me !

 

[Danger]

One clarification to MATLABdude's post is to point out that although I did recommend something that I thought might be a practical solution, I am not an engineer. I never finished high-school. I've built a lot of **** in my day, mostly from scratch, and I was a professional (technical-college educated) locksmith, but that doesn't count against the brainpower of most PF members. Listen to the professionals, not me.