NerdKits - electronics education for a digital generation

You are not logged in. [log in]

NEW: Learning electronics? Ask your questions on the new Electronics Questions & Answers site hosted by CircuitLab.

Project Help and Ideas » 2n7000 Mosfet light switch

June 30, 2012
by dmgctrl
dmgctrl's Avatar

So I've been trying to find a really basic write up on how to use 2N7000 MOSFET. For me the information seemed abstract. So I've built a circuit that shows how it works. I did a short video as well.

2 quick comments:

I haven't had a part break and I THINK I'm being careful YMMV.

I am not a writer. If any part of this is confusing unclear, please let me know.

The Project: We won't need the chip for this project, so I bought a blank breadboard. I'll be giving the MOSFET the on off signal from the 5v rail by hand.

First we'll need to setup. Most of this you can get straight from the nerdkits guide, but I'll walk through it quickly for clarity:

battery positive Pin 3 battery negative On the blue rail Voltage regulator on pins 3 - 1

Connect the +/- rails on the other side of the breadboard

I put the MOSFET facing the center of the board. On the left side of the mosfet I set the ground, on the right side I've set a LED, into the +5v rail. This is our light switch.

+5 Rail connected at 15. Connect LED positive side to pin 15 and negative to pin 13. Mosfet on 13 – 11 Connect to negative rails at pins 12 and 11 to the mosfet.

You can send the on off signal through the middle pin. In this project, if you don't set the middle pin you can get funky behaviour: Light always on, light lit dimly, etc. When you take the middle wire and ground the MOSFET that stops. Take the same middle wire and tap the +5 volt rail the light turns on fully. You can bounce between the 2 rails and turn on off the light.

On off movie

I'm currently using this setup to test the 2N7000's I salvaged from a RC car.

July 01, 2012
by Rick_S
Rick_S's Avatar

Just a word of caution. You should place a current limiting resistor between your LED and the 5V rail. If you don't, you will greatly reduce the life of the LED. HERE IS A LINK to an online calculator. At 5V, a resistor that is about 160 Ohms or greater should work fine and save the life of your LED.

Rick

July 01, 2012
by Rick_S
Rick_S's Avatar

Good write up by the way!

Cheers

July 03, 2012
by Ralphxyz
Ralphxyz's Avatar

Hey dmgctrl, you should add this to the Nerdkits Community Library.

It will just be lost here in the forum while in the library there will be a ready reference for others to see your great work.

I really like having a different view, thanks.

Ralph

July 03, 2012
by dmgctrl
dmgctrl's Avatar

Thanks for the idea Ralph. I'll sit down and write better directions, add the resistor and put it up in the library.

The current version I just finished used a switch to keep the mosfet grounded so the led doesn't light up unexpectedly.

July 03, 2012
by Ralphxyz
Ralphxyz's Avatar

That would be great!

Between the Nerdkit Guide and the Motors Tutorial and then your write up should really make it easy for some one to get started using the 2N7000 MOSFET and MOSFETs in general.

You could also experiment with different resistor between your 5V source and the center pin on the MOSFET.

Ralph

Post a Reply

Please log in to post a reply.

Did you know that our USB NerdKit comes with everything you need to get started with microcontrollers? Learn more...