P Channel Mosfet (switching leds).

Thread Starter

PVBLLLC

Joined Feb 6, 2016
3
Can some one tell me what's wrong with the attached sketch?
The p-channel fet/12vLED's won't turn off with the potentiometer.
I'm using a p-channel fet because the LED array I'm using has 5 segments with a common ground.
The arduino (bar graph sketch) and potentiometer work correctly with 9 volt LED's.
Please ref attached.
Thanks
 

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bertus

Joined Apr 5, 2008
20,102
Hello,

Where do you think the gate of the fet will get its drive?

Please post a propper schematic with the schematic symbols in stead of a drawing of the setup.

Bertus
 

dl324

Joined Mar 30, 2015
9,121
Welcome to AAC!
Can some one tell me what's wrong with the attached sketch?
You have the MOSFET connected wrong and probably don't need a transistor to drive the gate.
The p-channel fet/12vLED's won't turn off with the potentiometer.
I don't see a pot in your drawing.

A "proper" schematic would make it easier to read your circuit. When you post pictures or schematics, please make sure they can be read. I had to use a photo editor to magnify your picture to read the text.
 

Thread Starter

PVBLLLC

Joined Feb 6, 2016
3
Welcome to AAC!
You have the MOSFET connected wrong and probably don't need a transistor to drive the gate.
I don't see a pot in your drawing.

A "proper" schematic would make it easier to read your circuit. When you post pictures or schematics, please make sure they can be read. I had to use a photo editor to magnify your picture to read the text.
Thanks for the help guys!!!!
I'm not an electrical engineer, designer, etc.
Have combined other works to get where I am with this project.
I don't know how to generate a proper sketch and this is my first post.
Can you edit my set up sketch showing the proper connections for the MOSFET?
 

dl324

Joined Mar 30, 2015
9,121
I'm not an electrical engineer, designer, etc. I don't know how to generate a proper sketch and this is my first post.
That doesn't mean you shouldn't learn how to draw a "proper" schematic so that you can communicate in the language that EE's understand.
Can you edit my set up sketch showing the proper connections for the MOSFET?
This is how I interpreted your "schematic"; I added the ground connection between the battery and the rest of the circuit.
upload_2016-2-8_6-47-1.png
This would never work. You have the MOSFET connected backwards and the LED would always be on. If the MOSFET were connected correctly, it would not turn off properly because there's no pull-up on the gate.

This is how it should be drawn:
upload_2016-2-8_6-48-47.png
 
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