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I'm trying to control an RGB LED strip using a NodeMCU. I have been following the guide linked here. However, the diagram included in the diagram is rather unclear, especially for someone like myself who is new to electronics. This is the diagram:

enter image description here

All I can make out from the picture is "500 Ω". However, when googling for the resistor, I am unable to find exactly what I need. For example, on this AliExpress listing, I am unable to find any mention of "Ohms" and just get given an option of multiple "...R". "...K" "...M".

I would really appreciate it if someone could point me in the right direction as I am new to electronics and have found myself stumped by this relatively basic issue.

Thank you in advance for any help.

P.S. I am aware that the method used to step down the 12v to 5v shown in the diagram can be problematic and I am instead going to use a 12v - 5v car charger.

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    \$\begingroup\$ 500R is a shorthand for 500 ohm in many cases. Other examples of this shorthand include 1R2 (1.2 ohms) and 1k2 (1200 ohms). \$\endgroup\$ – ζ-- Aug 31 '18 at 3:38
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A 500 Ω resistor might be listed as 500 R. However, 500 Ω is not a common value - 510 would be much more common, and would be appropriate for that application.

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  • \$\begingroup\$ Thank you for your concise answer! That makes perfect sense. Possibly unrelated: in the article I linked, it was initially suggested to use a TIP122 but was then edited to suggest using an IRLZ44N instead. A) does this have any affect on the type of resistor needed? B) why do you think this was later changed? Thanks once again! \$\endgroup\$ – Rocco Aug 31 '18 at 3:44
  • \$\begingroup\$ @Rocco MOSFET gates are like small capacitors, so they have no resistance at first, until their voltage equalizes. Gate resistors protect the gate current source from that. Choose the gate resistor by assuming there's no other resistance, and limiting the current flow to what your chip can safely source and sink. 500 ohms should be fine, except for wimpier sources like op amps. \$\endgroup\$ – piojo Aug 31 '18 at 4:19
  • \$\begingroup\$ @piojo Ah I see. Just to confirm, using both the IRLZ44N along with the 510 Ohm resistors should work find then? \$\endgroup\$ – Rocco Aug 31 '18 at 8:55
  • \$\begingroup\$ @Rocco Assuming you're driving it with 5 V (not 3.3 V), I wouldn't worry about it. Though you'll want to touch them to see how hot they get. If it hurts, consider heat sinks or chunks of aluminum. \$\endgroup\$ – piojo Aug 31 '18 at 9:48
  • \$\begingroup\$ I think the NodeMCU's pins (D5, D6, D7) operate on 3.3v rather than 5v. However from the original article, there is no mention of this being a problem. Do you agree? I will be sure to check the temperature of them when I start using them as you have suggested. Best \$\endgroup\$ – Rocco Aug 31 '18 at 11:58
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"R" is an alternative way of writing ohms--it's actually a substitute for a multiplier (m, k, M, G, etc.) when there is none (when the multiplier would be "1"). In that alternative definition, the multiplier is treated as a decimal point, so "1R2" would mean "1.2 ohms". And "3K3" means "3.3 k ohms". "1R" is one ohm, "R1" is 0.1 ohms.

So your 500 ohm resistors may be labeled "500R". Though I don't think they would ever be labeled "K5", despite being logically the same number.

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    \$\begingroup\$ Thank you for your answer! What you are saying makes perfect sense and it's much clearer now. Thanks! \$\endgroup\$ – Rocco Aug 31 '18 at 3:41

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