Universal (theft) Protection for Electronic Equipment or Cars With Invisible Switch




I'll show how you can utilize a reed switch as a universal protection for electronic equipment or cars. All you need is a reed switch and a magnet. For cars you'll need a power relay to increase the switching capacity of the reed switch.

A pictorial and a video demonstrates how to build an invisible switch into a PC. A schematic is shown how to apply this technique for cars.

Step 1: How to Make an Invisible Switch in a PC Step 1

I'll show how to protect a PC with a hidden switch. You'll be the only one who can turn it on and thieves will not directly be able to turn it on unless they take your pc apart and start 'fixing' it.

The first picture shows the reed switch which we will use. It's a glass tube with two contacts which are pulled towards each other making contact when a magnetic field is present. You can reed(read ;-) ) more details on wikipedia. http://en.wikipedia.org/wiki/Reed_switch

For the PC we'll use a read switch with a make contact.

The first step is to remove both side pannels from the pc housing by unscrewing the bolts shown in the picture. After that the front panel can be removed by pushing the front panel retainers together with your fingers to unlock them.

Step 2: How to Make an Invisible Switch in a PC Step 2

Now that the front panel is removed, search for the wires coming from the on/off button. In my case, I had to check that I wasn't confusing them with the led wires. Once you've found the wires from the on/off button, cut one of the wires and strip both ends over a length of 10mm. You can see this in the second pictures.

Now we can twist our read switch to the wires. Once the switch is twisted on, we can tape it to the front panel using some quality tape, so it won't let go. Mount the reed switch on a place where the front panel is not very thick, otherwise we may not be able to operate the switch.

Step 3: How to Make an Invisible Switch in a PC Demonstration

With the switch mounted, the front can be put back on and the side panels can be remounted.

The reed switch is in series with the on/off button. This means the on/off button cannot be operated unless a magnetic field is present near the switch. You have to hold a small magnet close to the reed switch and push the on/off button. The pc will turn on and you can take the magnet away.

Some people are worried that the magnet causes problems with the hard drive. The field of a magnet at this distance from the drive is way too low to cause any problems. If you're still worried, you can place the switch as far away from the hard drive as possible.

Step 4: Protecting a Car

You can also use this trick to protect a car.

You can do this by glueing a reed switch on the inside of your dashboard and having some velcrow on the other side of the dashboard. Glue a magnet to the velcrow and you can stick your magnet to your dashboard activiting the switch.

Reed switches cannot conduct very high currents, so you'll have to connect a 12V car relay to it so you can switch larger currents. You can use this relay to break a vital wire in your car, like the contact wire behind your ignition key switch. You could probably also put it in your starter motor control wire or maybe your engine management, but you should check this with your garage for your specific car model because engine management systems can be sensitive.

The schematic shows how to connect it. I'm showing a reed switch with an alternating contact here, this can be usefull, although the relay usually also has an alternating contact. You can choose if you want the car to run with or without the magnet by choosing another contact on the reed switch or the relay.

Thieves usually do know all the standard alarm systems and protection systems but will have a hard time locating this protection since they don't know what to look for.



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    69 Discussions


    Reply 3 years ago

    It's very important to avoid magnets close to HDDs , but the metal case of the HDD is a shield and protection against magnetic fields btw.


    Reply 7 years ago on Introduction

    Hard drives have two extremely powerful magnets inside them.
    WAY, WAY more powerful than the magnet in this instructible.
    No one is ever concerned about getting their hard drives too close
    to other magnetically sensitive materials.

    Your concern is good, but flawed :-)


    Reply 10 years ago on Introduction

    the magnet needed is no where near strong enough to damage the hard drives. Hard drives have surpassed the time now that near by magnetic waves damage them. Unless those of a very strong power


    4 years ago on Introduction

    Mount the magnet in the mouse so you don't use it and bypass the pc switch altogether to simply turn on your pc with the mouse. Not likely to loose the mouse and if you do, you bigger problems :) Good Instructable btw!

    1 reply

    9 years ago on Introduction

    Very impressive. I like the idea. But I have a small suggestion to make. Forget the switch at all and just put in the reed switch. You could mystify your friends by just waving your hand over your computer case, (with a magnet concealed with a bit of slight of hand) and like magic it turns on. You are now a true master of technology.


    9 years ago on Introduction

    Your video was removed by Metacafe.  I don't suppose you'd make it available again.


    9 years ago on Step 4

    very nice. will use.


    you could also mount a magnet in the table under the PC and the reed switch in the bottom of the PC, so it sits just above the magnet then hook the reed switch to an alarm in such a way so that if the PC is picked up or moved slightly it would sound an alarm. That is another theft prevention device.


    I've been looking all over online and I can't seem to find reed switches, and the local Radio Shack, Circuit City, Best Buy, Hobby Lobby, Fry's Electronics, and (of course) Wal*Mart ALL yielded nothing. Anybody got a suggestion?

    3 replies

    Reply 10 years ago on Introduction

    Mouser is where I go for most of my discrete components.
    Here is the link to the page in there catalog for reed switches.
    The bottom ones are truly tiny little things.
    reed switches


    Reply 11 years ago on Introduction

    But wouldn't that also prevent the computer from being turned off? (Of course there stil is the OS shutdown/power off, but if you somehow disabled that.... :-) )


    Reply 10 years ago on Introduction

    If you make the switch again it will cause the PC to go into shutdown. If you make it for 5 seconds the power supply will shutdown without the help of the PC