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Smart Lock

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RnD Engineer

New Member
Hi guys,

I am intrested in making a smart lock ( I am a total novice and I have to study hard in order to make it of course). I am an electrical & computer engineer but I haven't worked on developing any product yet and I have a lot of gaps regarding microcontrollers, programming (generally in mechatronics) but I am willing to study hard.

I have seen a special smart lock which can be unlocked only when it is placed on a specific device. This device is IoT device. So you can send (let's say via a mobile app that I need to develop) a signal to this device to unlock the smart lock when it is placed on the device. This is a summary of what I am intrested in developing

As far as I can understand, lock's mechanism should use (probably) a small electromagnet that will be triggered with specific electrical signals that will receive from the unlocking device when it is placed there (maybe RFID tag has to be used in the smart lock and an RFID reader in the unlocking device in order to be able to recognize that the correct smart lock has been placed on it). So when the smart lock is correctly placed on the device, I can send a signal via my app and unlock it

Does this make sense? Probably (99%) this already exists (I have seen smth similar to it) so you may have come accross a similar project. I just like the idea of making a strong and smart lock that is going to work this way but I have no idea how to make this work or even on how to start on this

Any guidance will be highly appreciate it.

Thank you in advance guys
To make it more specific,
I think that I need a permanent magnet (solenoid) that will be used to lock the pin/needle etc. I need to find a way to provide electrical current to this permanent magnet in order to neutralize the magnetic field and release the pin/needle etc when the authentication has been done. The problem is that this permanent solenoid should be hidden in a housing and has to be small. So I have to avoid using cables. I have to find a way in order to provide the appropriate electrical current to the solenoid but I dont know what has to be done in order to make this work properly. Any ideas would be useful. Thank you
It's hard to envision what you have in mind. However, electrically you will need some kind of inductive connection, think contactless charging, and possibly a micro servo (google) to move a bolt back and forward.

How big do you think it would be?

Hi Mike,

thank you for your reply mate.

I think that I explained it totally wrong to you. It is possibly much more simple than it sounds. Ι have to draw my thoughts and post again. It will be much easier. Thank you again
Maybe a first question is what do you want to lock? My initial thought was a door, but maybe you are thinking of a cabinet or drawer.

The electronics would be similar in either case, but the locking mechanism very different with different drive requirements.
Hi JonSea,

thank you as well for your reply. To be honest I was thinking of making 2 different types of locks

The first one will be as shown below (so nobody will be able to cut it to but I need to penetrate the product) and the second one a regular locker for suitcases,drawers etc. Both of the locks will need a housing that will be made by me (maybe with 3D printing but not sure yet about it). So let me explain you more:

1)First, I am pretty sure that I need a solenoid magnetic latch like the one shown below:

The problem is that I need a customized solenoid magnetic latch because it needs to be small (let's say around 3 cm) and secondly, I want to avoid any cables to be show externally from the housing. So probably I have to buy 2 permanent magnets with a hole at the middle (correct me if I am wrong, I have gaps in electromagnetic theory :) ) and add a spring at the top of them. Metallic rod/needle will be passed through this hole and the magnets will keep this locked.

So probably I have to go the wiring around the magnets+the spring (around the customized magnetic latch) and fit the endings of the cables at the bottom of the housing (but inside the housing).

**broken link removed** **broken link removed**

After that, I have to make an external device where I have to hide a pcb that will allow me to transform it in IoT device and communicate with my app, an rfid reader and a circuit that will be able to provide sufficient current to the cable endings in order to neutralize the permanent magnets and unlease the spring (so this device should have a well made and accurate position on which I have to plug the lockers and to allow them to have electrical contactivity - device male endings and locks female probably).

So when the RFID reader confirms the ID of the lock, I will send a reply from my app in order to allow the circuit to provide current to the lock and done. I provide security for my belongings but mostly is something I want to make it because I liked this idea.

I hope that it is much more clear now to you on what I want to make. Probably I need to buy spare permanent magnets, a spring, a metal housing to place at the bottom the 2 magnets and at the top of them to add the spring + the RFID tag. Then I have to assemble all these in solidworks in order to be able to use 3d printer for lock's housing and for the "unlocker" and that's it.
I don't have much knowledge as you can see. I decided to start studying again and train my electrical engineering degree with this project (and to improve)

Thank you in advance and sorry if you read any "foolish" or faulty information
Here are a couple lock mechanisms you may not know about. These are from Elecrow but they're common on ebay too.

Yes mate, I have seen that. The problem is that I have seen a lock mechanism similiar to the one that I want to make by myself. I will send you a photo that someone sent to me (he knows what I want to develop). I couldnt figure it out how it works. I am posting it below in order to have a look to the mechanism and if you know how I can create such a mechanism for my needs


Because of my restricted knowledge on electromagnets, I am not sure what exactly do I need to buy and what to do in order to make this work the way I like.
I will write down my questions:

1)do they need solenoid permanent magnets?if yes, how do I have to place them (regarding their poles)
2)I think that I have to build a customized armature (two permanent magnets,spring + the metal housing for the magnets and the spring). If I am totally wrong let me know
3)Do I need coils around the armature inside the housing? Do I need to connect on magnets (or whatever it is needed) the endings of the coils or I just need to let electricity flow through the coils in order to neutralize the magnets and release the armature?
4)How much current will I need?

These are few basic questions that I have. Thank you again for your help and your time
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