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Touch sensor connected to magnetic lock Answered

Hi everybody, I would like to know if anyone can help me for this idea. Indeed, I would like to create a touch sensor which will be connected to a magnet system. To be more accurate, the idea involve the same process as a touch screen phone where one needs to do a pattern with 4 touch sensitive cases . The pattern would create and electrical impulse, which would unlock the box by detaching the magnet. So in a nutshell I will need a touch sensors pattern programing that would send an electrical impulse to detached the 2 magnets. I need this system so it could help me for my 1st creation. It needs to be very small to fit in a box of altoids candy for example. As I said, as a 1st creation I am completely lost for all theses "programmation" skills required. Thank you for your help. Beniver


Hi everyone,

I have been very busy so I couldn’t do anything yet. However silentbogo you made a good point concerning the CapTouch button.

I have been checking there and there and actually I found on internet the new Wallet called Iwallet using a latch lock to open with a finger print recognition. I really think to drop the magneic lock.The dimension of the wallet are perfect and the only difference is that finger print instead of the common touch pattern that I want to use. So I guess it s possible to make it, just need to figure out how ? :)

Good idea, but you need some adjustments to the concept:

1) Those types of locks use linear actuators. It is fairly easy to find those (you can even modify a small valve actuator used in water flow control). Another way around is to use micro-servo or micro-stepper motors + mechanical locking mechanism.

2) Laptop touchpad is OK and it is not too hard to connect it to Arduino (most pads work on PS/2 interface), but it will be easier to make a regular CapTouch button matrix (you'll only need couple of pins and no special knowledge). This way you could even use LED backlight behind PCB to indicate which button you already pushed!

I might make a similar touch panel in a few days, but the actual locking mechanism you are looking for will be way too big for Altoids box.

will you use a magnetic pattern recognition sensor ?

Perhaps a capacitance circuit? Somethin similar to a lamp which switches on/off with a touch anywhere on the metal?

Dear Downunder35m, that is perfect ! You are absolutely right concerning the touchpad from a laptop. Thank you so much for the links too. I will proceed and as you say do some experiments. I will post also in the future how the project is evolving. Once again, thank you for your reactivity and your help !

You're welcome!

If I think I have a working idea I post, that's how a community works ;)

Keep us posted about the progress and if all is good post an Instructable about it, I am sure a lot more people would be interested in the touchpad-Arduino connection.

Dear Downunder35m thank you for your advice. I have been thinking about those new miniature arduino and instead of a magnet system a latch lock could be fair enough. That would be a 1st step to make a really small system to put it in an altoid box. About the keypad my only problem is that I want my surface to be blank and use sensor under it so it could look way more esthetic. I guess I can find some tutorial (not really sure about that) to use an arduino to connect the key pad to the latch lock but as I don't want to use key pad I am kind of lost about how I can use a touch sensor on a surface but hide the system under it. Any help would be much appreciated. Beniver

As I said the most elegant solution would be the touchpad from a laptop or similar in size.

Problem is that I could not find any real documentation about using them outside an OS and without drivers.

If there is a feasable way of connecting them to an Arduino it only leaves the problem of writen the right code for a pattern recognition (not saying this is an easy problem though).

Edit: I rest my case ;)

It can be done if you look in the right places:



Maby this gives you something to experiment with before building the final box?

I am quite good building small but I see no way to fit your project into a small tin can.

A mouse pad from an old laptop might be small enough to be used as the input device but it would also require a way to read it, not 100% sure if that is possible with a small Arduino.

If your skills are god you can make your own magnetic lock from old relais, attach a pin and make sure the pin can move freely inside the lock.

It is the same system used on cheap electronic safes.

Maybe disguising a normal keypad as a touchpad would work for your purpose.

They mostly use little spring plates covered by the plastic with the numbers on it.

Conductive rubber as a replacement for the plastic foil and spring contacts could work if you add tiny spacer rings around the contact areas.

When you swipe over the contact areas it will be the same as entering the code manually.

But you might have to test first if conductive rubber is good enough for those keypads otherwise use copper foil in a similar way (the sticky tape one used in electronics).