Introduction: Proximity Sensor With 2N7000 Mosfet

FET Proximity Sensor

This very simple proximity detector circuit will sense over 1 meter range with very few components. Output can be modified to drive a relay, power transistor or mosfet .

Step 1: For Maximum Sensitivity, R2 Should Be of a Large Value ( in the 1000 Mohm Range ) . You Will Have to Make It.

Step 2: You Will Need : 1) a Match 2) a Small Length of Wire. Wind Wire Tightly on Both Ends of Match to Form the Resistor. You Can Paint the Resistor With Clear Nail Polish to Protect From Moisture.

Step 3: Transistor Q2 Amplifies FET Current to Drive LED.

Step 4: Calibrate Potentiometer VR1 for Minimum Brightness of LED. Watch Video for More Details.

Step 5:

Comments

author
deathofme made it! (author)2015-08-07

what can this be used for? what are some of its applications that won't mess up the fet?

author
Omnivent made it! (author)2015-05-12

Nice, but don't crumble any plastic bags or similar near it. The MOSFET is very easy to destroy due to the high gate impedance.

With a speaker on the output, you can use it to see what materials are unsuitable for sensitive components storage (almost any) - just keep your distance to keep your MOSFET :).

author
acheide made it! (author)2015-05-12

What kind of wire and what size/length for the resistor?

author
simpletronic made it! (author)simpletronic2015-05-12

Any kind of wire will do ( Not insulated ) . The length of the resistor is the length of the wood match. Make sure it's perfectly dry. Thanks for commenting !

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Bio: Music: my profession for over 40 years... Electronics: my beloved hobby always.
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