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Need some help with Electromagnetic locks, LCD Screen, Smart card Reader and Battery Power! Answered

Hi All,

I am designing a locking device (see attached image) that will house a smart card reader, a small LCD screen (roughly 80mm x 20mm) and a small electromagnetic lock that will need to withstand reasonable force.

The overall device will be no bigger than 140mm x 80mm x 40mm

I would like to know whether a rechargeable battery would be able to power the LCD screen, electromagnetic lock and smart card reader. If so how big and what size would that battery need to be?

How would an LCD screen be programmed to take information off of a magnetic strip and display it on the screen?

I would also like to know some names for the components that would be required to operate all of these components.

Thank you to anyone who comments. 



4 years ago

Your images looks great, at least in my imagination, so could you please add them?
Or am I missing something something, as I can't see your images here.

Can't help you with all but might have some ideas for power supply and locking machanism.

If low power consumption is a must (battery operated over long periods of time?) you have to start with suitable components and tricks for the task.

That means main focus for parts selection is their low power consuption.

for example you want to use a simple LCD display but nothing with a backlight that is constantly switched on.

If security is your aim you also need to mount all electronics on the inside and if possible use RF ID tags instead of a card reader, magnetic cards are easily copied and card readers can be tampered with by using some electronics to check millions of codes in a few seconds. Also RF systems use far less energy to run.

Screen, electronics and reader should be able to run on 3V, if not 4.5V should do.

You also have to option to use step-up-converters to get up to 12V from a 3V supply, but that should be the last option as they also consume power for stepping up.

Screen only needs to come on if a RF tag is in range or for even less time to just confirm the actions.

As for the locking system....

We could talk days about all sorts of variations and types but I think for starters you should not go for an electromagnet.

Firstly you need quite big holding forces for a suitable locking bar, which means big magnet and high power consumption.

Next problem is reach, to be able to provide good movement you need a quite long magnet, which makes alignment and free play a big concern.

Using some non-direct locking mechanism, like a roll bar, clamp or similar requires even greater forces.

There are several ready to go options available for electrical locks but most require at least 12V to operate.

Some of the simpler door latches just hold the door in place using the original lock, but I can't really recommend them as they are not really safe.

Better option is to use a system that is complete in terms of the frame and door part and use and interlocking system, but they are quite expensive.

I would suggest to use a small electro motor with reduction gear box attached, provides great forces at low power levels.

With that you could include the locking system from an old secrutiy screen door, you know the type that "folds out and down" to grab into the frame like a finger?

Another good option is to simply drive a strudy steel round bar out with the motor, simply use a fine thread inside the locking bar and the motor with spindle to drive it in and out.

With access to some machinery you could also design your own locking system or salvage a bolt system from an old safe.

You might want to check you local locksmith and ask for some electric and electronic locks to see as well as electrical "door openers" as used on many commercial and residential entry doors - the kind where someone presses a button and hear the buzz in the door and can push it open.

Gives a good overview on the option and good ideas on how to incorporate something into your project.

I would also suggest to either use a small solar panel to keep the batteries charged or to build a tiny generator that is driven by the door (like a small DC motor driven by a spring loaded belt or that runs with a roller along the floor).

If you don't want to re-design the entire wheel you might also want to check RF ID reader systems more closely.

You can get reasonable cheap systems that offer multiple outputs and integration into computer systems.

Some suppliers also offer RF ID kits for doors already, mostly without a screen but still you would get a suitable lock, battery system and tags in one go.


4 years ago

In the top search box where is says 'let;s make'-----------, type in "electronic locks" and hit the little magnifying glass icon to go. Read up on electronic locks from the instructables. Then you could search for "RFID locks" or "RFID" to read up on smart card readers. The trick is to substitute the keypad with an RFID reader. Good luck.