I was recently connecting an LED strand to my Arduino nano using the following wiring diagram: image schematic here

I was using 10k ohm pulldown resistors in order for the LED's to be off when the Arduino is outputting a low signal but the power is plugged in. However the LED's are still on (very dim but noticeable). I was wondering if adding a bigger pull-up resistor would fix my issue?

Also if this helps I'm using the following hardware: Arduino Nano rev 3 10K ohm resistor 12V 6A 72W power supply 300 LED strand.

Thanks in advance!

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    \$\begingroup\$ Where do these terrible wiring diagrams come from? \$\endgroup\$ – Ignacio Vazquez-Abrams Dec 13 '13 at 5:19
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    \$\begingroup\$ Fritzing.org. I get that they're super helpful for newcomers to electronic prototyping, but they're also not helping teach schematics at all. \$\endgroup\$ – JYelton Dec 13 '13 at 5:25
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    \$\begingroup\$ @Ignacio: there is a small clue at bottom right of the wiring digram :-) I think the tool can produce schematics. Their website says "Schematic View - no specific tutorials yet" :-( I'm sure it can be done though. Also this. Quentin: please edit your Q and add an image of Fritzing's "schematic" view. \$\endgroup\$ – RedGrittyBrick Dec 13 '13 at 10:35
  • \$\begingroup\$ @Ignacio: Sorry, I guess you mean: In which dark corner of the intertubes did Quentin stumble upon this diagram? \$\endgroup\$ – RedGrittyBrick Dec 13 '13 at 10:42
  • \$\begingroup\$ I stumbled upon it here: jerome-bernard.com/blog/2013/01/12/… . I didn't actually make the schematic so I can't get the actual schematic view). I see now what's wrong with the diagram now, oops! Thanks! \$\endgroup\$ – Quentin Dec 13 '13 at 17:16

The pull down resistor is in the wrong position, it should be on the output of the PWM pins.

You only need them to keep the LEDs off when the Arduino is off or if the Arduino pins are set to the INPUT state. This is the default startup of the Arduino which is probably why you are seeing the LEDs coming on faintly. Either move the resistors to the PWM outputs or change the code to set the pins to OUTPUT.

By the way, what FET are you using?

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    \$\begingroup\$ I cant tell if the pull down resistors are all wrong, or just the schematic is wrong. The Red PWM is pulled down, but not the Blue or Green. \$\endgroup\$ – Passerby Dec 13 '13 at 6:20
  • \$\begingroup\$ Hi, I am using the IRFZ44 FET (datasheet: vishay.com/docs/91291/91291.pdf), thanks for the feedback, I will move the resistors to the PWM outputs! \$\endgroup\$ – Quentin Dec 13 '13 at 17:13
  • \$\begingroup\$ Let us know if it worked \$\endgroup\$ – geometrikal Dec 13 '13 at 22:47

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