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In these 2 examples, they connect the source to the gate with a 10K resistor, and both source and gate are connected to ground (edit clarification: gate connects to ground via 10K resistor - source connects directly to ground). The gate is connected directly to the PWM pins.


In this example, the 100-220 ohm resistor is between the gate and the PWM pins on the Arduino. The gate is not connected to ground nor to the source.


I'm new to this, but this seems like a pretty big difference.

Which is right or wrong?
Are their advantages or disadvantages?

(edit - now with pictures from each link included in the question)

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    \$\begingroup\$ Please, paste the schematics as pictures. Nobody will click the links \$\endgroup\$
    – fifi_22
    Feb 22, 2021 at 19:15
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    \$\begingroup\$ "both source and gate are connected to ground. The gate is connected directly to the PWM pins" makes no sense, that means the MOSFET gate-source will always be zero so it will never turn on. \$\endgroup\$
    – Finbarr
    Feb 22, 2021 at 19:20
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    \$\begingroup\$ Please paste SCHEMATICS, i.e. proper circuit diagrams. Nobody's going to bother looking up the pinouts and figuring it out from those cartoons. \$\endgroup\$
    – Finbarr
    Feb 22, 2021 at 19:39
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    \$\begingroup\$ They both work. Pay attention to resistors value. You can combine two schematics. \$\endgroup\$
    – user263983
    Feb 22, 2021 at 20:18
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    \$\begingroup\$ it's essentially "do i need to pull down mosfet gate when using MCUs?" both ways work. the MCU should pull down the gate when the pin is set low by the program. a pull down might help/be needed if your pins have a prolonged indeterminate state at power-on and you don't want the light flashing randomly for a few millis. I would not use resistors between the GPIO and gate if you have all of : a lot of gate capacitance (common with logic level fets), 3.3v pins, a PWM frequency higher than 10KHz. \$\endgroup\$
    – dandavis
    Feb 22, 2021 at 20:18

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Thank you all for the information in the comments. I'm composing them the best I can into an answer.

I believe I now understand: The 10K resistors are a "pull down" to prevent potential indeterminate state issues. The 220r resistors are to protect the MCU from potential current spikes.

I don't intend to create a Schematic for the 3 examples in the question, but here is a schematic of what has been suggested as a potential answer in the comments.

enter image description here

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