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I'm in the process of building my Gauss meter to measure the strength of magnets and I came up with an awesome idea for the on/off switch. I didn't want any switch visible from the outside so I made a circuit that allows the magnet you are testing to turn the device on and off from the outside. In the video, I go into how the circuit works in a bit more detail as well as show it in action.

Step 1: What You'll Need

This is what you will need to build this circuit:

Reed Switch x2

N Channel MOSFET x1

P Channel MOSFET x1

100k Resistor x2

6.8k Resistor x1 (Not critical, can be a bit above or below)

Step 2: How It Works

The P Channel is off when the circuit is done being assembled. When the switch on the right makes contact, it turns the P Channel MOSFET on which causes the N Channel MOSFET to turn on. This latches the circuit on.

When the switch on the left makes contact, it causes the N Channel MOSFET to turn off which subsequently turns the P Channel MOSFET off with the rest of the circuit.

Here is a link to the simulator I used in the video. You can play around with the switches and change values to see what happened.

Step 3: Applications

You could use this circuit for anything you want to have a hidden switch. You could build a secret compartment that can only open with a magnet held in a secret spot. Let me know in the comments what you could use this circuit for.

Thanks,

Anthony

About This Instructable

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Bio: Electromechanical Engineer, Product Designer, Maker. I love to make prototypes and teach others in the process. I graduated from UCF and spent two years working ... More »
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