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A reed switch is an electrical switch operated by an applied magnetic field, here’s a simple how-to on using one to turn on a computer.

Phillip Torrone

Editor at large – Make magazine. Creative director – Adafruit Industries, contributing editor – Popular Science. Previously: Founded – Hack-a-Day, how-to editor – Engadget, Director of product development – Fallon Worldwide, Technology Director – Braincraft.


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Comments

  1. Mr. Obvious says:

    Magnets in close range to sensitive electronic components…ya, that seems smart.

  2. Aaron Grando says:

    I like the idea, but yeah, I don’t know how comfortable I would be having to stick a *magnet* near my computer whenever I turn it on.

  3. computerwiz_222 says:

    wrap the wires around the reed switch – nice electronic know how

    what ever happened to a good old soldering iron?

    I love the idea though… If you really wanted to, you could disuise the switch in your keyboard or something… Place the magnet on the num-lock light and presto… a little safer no magnets near your precious data.

    You could use the unused pairs on ethernet to mount the switch inside a router or something too…

  4. Earl Jr. says:

    Relax. With the shielding on most computers, it would take a fairly powerful magnet in close proximity to the hard drive to degauss it. Remember; inverse square law.

  5. BigD145 says:

    For a less obvious turn on you can use a ring with a magnet on it and just press your knuckles, and thus the ring, over the reed switch and use your thumb to turn the computer on.

  6. justDIY says:

    security through obscurity, tsk tsk tsk!

  7. vic says:

    A magnet this small will have a very fast vanishing field. It’s a dipole so if I recall correctly it will decrease in 1/r^3 (not 1/r^2).

    Despite what the commentary says it would also work through non magnetic metals, like aluminium.

  8. Dax says:

    I have a reed switch (connected to a relay) in-line with the fuel pump on my Jeep.

    No fridge magnet on the dash = Jeep starts (loud) but only runs for 30 seconds.

    Fridge magnet on the dash = Jeep runs

    Poor man’s car alarm.

    PS: To anyone thinking they can steal my Jeep now, replace dash with actual location of reed switch ;-)

  9. EllisGL says:

    Would be better if you modded the PSU along with this. For most this would be the ATX power supply. Just do what he did but put inline of the wire connecting pin 14 (green). Of course the magnet would have to stay there durring operation of the computer.

  10. Simon says:

    What about a circuit to switch on the PC via IR remote
    (e.g. using remote from TV card or Creative Audigy, etc…)

    The circuit would need to take power from the 5VSB pin of the ATX PSU making it more complicated than a simple read switch, even more so if it was to respond only to 1 button on a specific remote.