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Topic: PWM problems when controlling a MOSFET gate (Read 74 times) previous topic - next topic

scoyne122

I am working on a project that involves using an Arduino to control the brightness of an led. The LED takes in 12v to power, so I am using an external power source and connecting it to the ground via a MOSFET controlled by my Arduino Uno.

This issue: no matter what component I try to power, it "flashes" whenever the analog pin output is an intermediary value (i.e. not 0 or 255). Interestingly, the brick in my power source has an LED that will start to flash the same way.

I am confused why the lights work perfectly on full power but have this flashing issue when PWM techniques are used. I attached a diagram of my setup, so any help would be appreciated.

Thank you!

Also, here is the datasheet for the transistor: https://www.arduino.cc/documents/datasheets/MosfetTransistor.pdf

PS I come from an all software background, so I would appreciate hardware explanations in layman terms

larryd

#1
Jan 13, 2018, 09:53 pm Last Edit: Jan 13, 2018, 09:57 pm by larryd


You need the correct MOS FET, that one needs 10 volts to turn on.


Make sure your load does not need current limiting.
Use a logic level transistor.
Use a gate resistor.
See the Q3 circuit.

Click on the image for full resolution.




No technical PMs.
The last thing you did is where you should start looking.

jremington

#2
Jan 13, 2018, 10:16 pm Last Edit: Jan 13, 2018, 10:18 pm by jremington
That particular MOSFET won't work properly with Arduino, because it requires 10V on the gate to turn it on fully. Use a logic level MOSFET, like this one.

Always use a current limiting resistor between the output pin and the gate, 150 Ohms minimum.

If the power supply LED is blinking, that may mean that the supply is overloaded.

raschemmel

#3
Jan 13, 2018, 10:16 pm Last Edit: Jan 13, 2018, 10:19 pm by raschemmel
Sparkfun has logic level mosfets.

WHAT "analog pin output" ?
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