Hello everyone, I'm new here, and I'm currently working on a project for my final college assignment. I'm inspired to create a theft detection system for equipment (similar to those in retail stores). However, such a system seems to be quite expensive, and I haven't found modules or sensors suitable for Arduino. So, I'm thinking of using a 4-6 magnetometer like HMC5883L and small size rare earth (neodymium) magnets. The idea is to attach the magnet to the items to be tested, while the magnetometer will be placed at the entrance or exit, maybe will look like picture below.
The threshold value will be set on the magnetometer, so if someone carrying the item passes through the magnetometer, there will be fluctuations in the magnetic field value exceeding the threshold (caused by the magnet), triggering an alarm.
My question is, can attaching such magnets to electronic devices affect or even damage them? I'm considering implementing this system in my friend's music studio rental, where theft of equipment such as guitar pedals, microphones, and jack cables by irresponsible users often occurs.
Thank you, everyone. Your answers will be greatly appreciated.
~Choirul
Affect may be, damage not very likely. Ask your friend for some tests with the various items. Also test how your magnetometer behaves when the items are moved across the studio.
I suggest you continue your research, some items are sensitive to magnetic fields such as floppy disk. Also there are several existing systems you need to check and determine how they accomplish it. Check into the security tag system, I think it is less then $0.02 per item. This gets deactivated when the item is checked out.
Buy the sensor and experiment with a couple of magnets. I am pretty sure that you will find the idea unworkable, because magnetic field strength drops off very rapidly with distance.
Due to the nature of a dipole field, the (physically) smaller the magnet, the more rapid the dropoff, so they affect the magnetometer only at rather short distances.
Another approach would be to wind many turns of wire around the doorway frame. A magnet moving through it will induce a small AC voltage, which might be detectable.
Yes, you're right. The tags themselves are indeed very affordable, but the readers located at the exit door can cost up to thousands of dollars. That's the issue for some small-scale businesses.
I've actually tried it. I used a neodymium magnet, size is about 20x2 mm—small but quite powerful. Within a distance of approximately 20-25 cm, the sensor can detect changes of around 1 uT. So, by creating two sides of detection poles (right and left as shown in the picture), I might be able to achieve a distance of around 50 cm. Do you think its good?
hahaha yeah, the picture is just illustration, iam forget to tell about the real distance, maybe just 50-60cm. At least it's sufficient for people passing by.
Its the magnet that i use, really small but quite strong.
And the photo below shows the detector in action, detecting the presence of the magnet. I've set a fluctuation threshold of +/- 0.8 uT from the average value read by the sensor (I have programmed it to continuously update the average value every 10 seconds). So, if the magnet is positioned in the middle, at least the lights on both sides of the detector should on.
Cool project, but you might consider false alarms from magnetic earrings, buttons, tie clasps, magnetic clasps on purses or briefcases, earbuds, etc.. If false alarms are frequent enough, the secondary inspection becomes lax. For example a potential thief could social-engineer around the system by wearing a strong magnet repeatedly until the guard waves them through or turns down the sensitivity.
How much of that answer was written by AI - it stands out a mile.
@choirulumam300501
If your studio uses magnetic tapes in any way this is a big no no.
I also can't see it being very effective as a pocket full of coins could set it off as well.
You might think those magnets are small but they are quite large I have been using 5mm diameter magnets in by last project.
Im not sure about the magnetic tape, i think there is no magnetic tape in my friend studio. By the way, i tried to detect some object too. Coins, Phone, car keys, or other "small" object not really triggering the sensor (At least if not too close to the sensor), so if someone is carrying those objects just passing through the sensor area and not intentionally 'attaching' those objects close to the sensor, it seems unlikely to trigger false alarm. Do you think it's a good thing?
what if some equipment like guitar pedal, microphone, or jack cable? do you think it will be affected or damaged bcs of the magnet? Because the equipment I mentioned earlier are often the target of theft.
In general magnets have no effect on electronic equipment.
On laptops magnetic fields can damage hard disc drives and floppy discs but that is about it.
Note that in the UK at least some coins are magnetic and some coins are not.
So, the magnet will have more negative impact for magnetic memory device, am I right? By the way in my country (Indonesia), most coins are made of non-ferrous materials, such as silver.
