Hello. I want to understand the circuit of a disc lock for scooters. The disc will be attached to the wheel’s disc and make a loud sound if it is moved. The pictures are from the circuit. It as a speaker, the black ic that I think is the accelerometer, a cap, an inductor, and some resistors. It is powered by six lr44 batteries. Could you help me to understand it? Thx.
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Hi Edwin
Welcome
A google search brings up plenty of places to purchase one of these but unfortunately zilch in the way of technical information.
Searching the numbers on the PCB brings up light globes for one and nothing for the other.
What exactly do you need to understand that is not covered by any user instructions provided ??.
It will be a mechanical/electronic lock, a vibration sensor and a very loud squealer.
That black blob in the top pix could well be the batteries in a protective heat shrink sleeve. If so it is a pretty cheap and cheerful way to mount them. Then again it could be an inductor or something else entirely.
I note that only the resistors have any markings on them so the rest is anybody’s guess.
I would not expect much of a response without more info unless you can be lucky enough to find someone familiar with this device.
Cheers Bob
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Hi. The black blob are not the batteries. These are located in another location.
I need to understand the circuit works and how it detects the movement.
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Hi Edwin
Why ??? If it works that is OK is it not.
For that you are probably going to need the schematic or a lot better technical description. Good luck with that.
If the components were identified you might be able to reverse engineer the device. But as you are the one with the thing in front of you it is you who would have to do that.
Or as I said, someone with enough familiarity to help out.
WE, as in Forum contributors as a whole don’t do too bad I don’t think but miracles might take a bit longer.
Cheers Bob
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Hey, @Edwin308107, and welcome.
As Bob said, without additional information we can only guess at how that part would work. If you want to trace out the PCB board and write out all the model parts and resistances, we might be able to do more, but it’s unlikely.
Hello. I just want to have of how the circuit detects movement and get a basic understanding of it. I do not have the schematic and the names of the components missing the names.
Any idea of how to identify the black ic, which seems to the brain? does it detect the movement and acceleration?
Best, Edwin.
Hello. Attached there is a pic of the large piece on the back of the circuit. It seems to be an inductor.
Hey @Edwin308107,
It’s definitely the brain, that’s the whole point of the IC, but it could be anything from an accelerometer to a timing IC. There are a lot of 8 pin ICs out there and without a label on them we cannot say for certain what they are.
From what I can tell here, the red and black wires are positive and negative, which means the blue and yellow are going to be where the logic of the circuit is being communicated to the lock.
From there, however, we would at least need a circuit diagram that clearly shows the connections to ascertain further.
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Hello Jane. The blue and yellow labels go to the large piezo speaker. Someone told me that they use the piezo speaker as a cheap motion detection sensor. Best, Edwin.
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Hi @Edwin308107 ,
Based on the big coil you have discovered, my suspicion would be that this is what is used to detect movement. This lock is designed to be mounted to a big hunk of metal in the form of the brake disc, so any change in position of the lock and the disc relative to each other will cause a detectable change in flux in the coil.
This is one of the annoying ones where we are unlikely to get a perfect understanding of the inner working of this thing based on the limited information you have available, but this is my best guess. The Piezo buzzer can definitely be used as a vibration sensor, but if that is what’s happening here, there wouldn’t seem to be a reason for this coil to also exist. A combination of both is also a possibility.
Let us know if you end up getting a definite answer on this one!
