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Fun uses for Reed Switches? Answered

Reed switches are electro-mechanical devices that opens or closes a circuit when a megnetic field is present. They come in normally open and normally closed designs and range from the size of a grain of rice all the way up to several inches long. A relay, another electro-mechanical device, is comprised of a reed switch and an electromagnet trigger built into one housing. Common uses for reed switches (not counting relays which are used in virtually all electronic devices) include the 'pick ups' on bicycle computers and the sensors on window and door alarms. I just ordered a bunch of reed switches and I need your help in coming up with ideas for what to do with them. Post up your ideas for some things that could be made or modified to be triggered by a magnet coming in close proximity to a reed switch. Remember- the magnet does not have to touch the switch, just get close enough that the magnetic force trips the switch. The stranger and sillier your ideas are the better. Note: this is not a contest and there are no prizes. by posting an idea you are giving your consent for anyone who reads it to use your idea. Posts about integrating reed switches into knex firearms will be ignored (no offence, it's just not my cup of tea).


Bike computer.
Wiith an Arduino and a LCD you could use it to build your own bike computer

You could make some kind of secret lock on electrical devices, so that the device could only be switched on by a magnet.

It's all right ,most of the alarm lock products have the switch in it and to work with the magnet together.Like the devices for door and window alarme anti-effraction .

Here's an idea that I will make an instructable later, but people can do it now if they wanted to. Please don't post this instructable or if you do any you got the idea from me just say so in the instructable. I was going to buy 2 micro usb drives (really small ones) for about 8 bucks apiece, solder all of there pins together except ground(soldering a totoal of 6 pinstogether). You would then connect the grounds together using a spdt reed switch so it would normally show your computer one usb drive, but when you put a magnet on it it will show the other usb drive. Put all of that (excluding the magnet) in an enclosure. In the end you can store secret stuff on the normally off usb drive. It's the ultimate hiding place!

Unfortunately, this would not work. USB requires a dedicated (addressed) port for each device. You cannot connect USB ports in a daisy chain fashion. If both are connected simultaneously, only the first to respond to the query signal would be active. The other would be ignored but continue to pull current, possibly exceeding the rated current of the port (500mA).

that's not exactly what I meant, at any given time only 1 USB device would be connected. You either have the normal default drive connected, or by attching a magnet you disconnect the default and connect the secret drive

That would be fine as long as the previous drive is safely unmounted first. I would recommend a digital switch for both USB data lines, rather than mechanical.

. How will the "standby" unit pull any power if the ground is lifted? Won't it be dead? . Wouldn't it act just like you unplugged one unit and immediately plugged in the second, when "flipping the switch"? . . Some type of break-before-make arrangement might be desirable to keep from overloading the port.

I believe he was talking about just switching in and out just the second device. I still wouldn't recommend this setup using a SPDT switch to switch one out while switching in another. It would be disconnecting a drive without properly closing it, risking data intended for the drive not being written. I also would never recommend using the ground line to switch any device on and off. Ground should be the first line connected and the last disconnected.

That is an awesome idea. My wife and I share a computer and i wouldn't want her to find my collection of... ...shipping confirmation notices for birthday presents i haven't given her yet... on the computer. I hope you will build this and if it works post an instructable. I know generally magnets and computer parts don't go together so you'll have to be careful with your placement of the device inside the computer case.

I've read about it and magnets don'treally do anything to anycomputer stuff except floppy disks. The only way to do anything to a computer with a magnet is to take an EXTREMELY powerful magnet and wave it just above the harddrive. And also the magnet wouldn't reall ever be there, it's just the "key"

I just remembered a use I had for one years ago. I created a "electronic heads or tails game" using a CMOS flipflop, that semi-randomly displayed even or odd number of LEDs (one, two, or none). When someone else held the box, and pressed the button, it would be "somewhat" random, so their guess was about about 33% accurate. When I handled the box, a slightly magnetized ring ornament, would flip the reed switch and I would get "odds" all the time (no, I didn't cheat people out of their money with this, it was more of a "wow, you can predict the future" kind of a thing ;-) ).

Make an interactive sculpture with parts that move and others that light up based on the viewers movements (with a magnet, of course). I was thinking of a hand passing in the center of a tube and the tube opening up like a flower.

Replace all the keys of a synthesiser with reed switches, covered by a blank sheet of plastic. Play it with gloves with small magnets in the fingertips.

Connect a high-voltage supply to a door handle, the circuit completed by a normally-on reed switch. When you open the door, the magnet in your rings makes you safe. When anybody else opens the door...

Magnets on pet-collars will let them open the e-mag locked pet-flap.

Bury a secret lair under your garden, and hide magnets in garden ornaments - the lawn will only be hydraulically-lowered when the ornaments are stood in certain location around the garden.

That keyboard thing was MY idea, but i thought of using a calculator!

Put reed-switches behind a dart-board, and magnetise the shafts of the darts - wherever you hit, the reed-switches will control a large illuminated display to show your score.

Mounted above a door, or in a dresser drawer, a magnet could be placed on the movable potion (door or drawer) that would "trip" (on or off) the switch and set off an alarm or a warning ("Danger, Will Robinson!")

I'll get the ball rolling: Replace the button on a garage door remote with a reed switch and afix it to the inside of the garage door. A magnet placed in just the right spot on the outside of the door will open it. Much safer than leaving a key hidden under a rock!