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+--- Thread: DIY electromagnet based time-lock devices (/Thread-DIY-electromagnet-based-time-lock-devices)
RE: Electrical engineer wanted - magnet cuffs idea - Tinker D - 01 Apr 2024
Ok, here is a bit of information that may or may not be helpfull, but it’s worth noting.
Magnet cuffs are not new. We had them in the 70s. Way before internet, Bluetooth and microcontrollers. I don’t have any pictures of these, but this is the best discription that I can think of. I could be wrong.
A magnetic coil around an iron core was mounted on the wall or floor. The wires were connected to a timer and a 9volt transistor battery. Simple and effective. Like I said, that was a long time ago.
Another device had a AAAA set of batteries, that they don’t make anymore, that connects to the electromagnetic. Once the battery has been connected to the magnetic, the time starts. The magnetic will not release until the battery dies. That can take hours or even days.
Adding a resistor between the two poles of the battery will drain the battery faster for a shorter time.
These were very crude and cheap.
Now, a little bit about electrical magnets. Electrical magnets need lots of power to pull the target to it. But, once the magnet makes contact, it only needs less than 1/2 power to hold the target. So here is a little test for you.
Mount a strike plate to a large board. Place your electromagnetic on the strike plate. Now, connect a 1.5 volt battery to the magnetic and pull. Then add another battery, making 3.0 volts and try again to pull the magnetic apart.
Keep adding batteries until you can’t pull the magnetic from the strike plate.
Have fun
RE: Electrical engineer wanted - magnet cuffs idea - Like Ra - 01 Apr 2024
I think these threads can be merged: https://www.likera.com/forum/mybb/showthread.php?tid=63
RE: Electrical engineer wanted - magnet cuffs idea - ltxrob - 01 Apr 2024
I made something similar in the past.
All ran off a 9V battery.
Used a 12v E-mag
A LM7805 to step the 9V down to 5V for the relay control board that @Like Ra mentioned
That way you can set a time delay before opening, or if all else fails the battery will give up sooner or later
RE: Electrical engineer wanted - magnet cuffs idea - Tinker D - 01 Apr 2024
Depending on the load, the 9 volt can last for almost a day or 1/2 hour.
The more current the load draws, the faster the battery will die.