This might not even be the right place for me to ask, but I hope somebody can help;

I have an arduino mega with 4 PWM outputs (5v, fitted with 220 ohm resistor) that I would like to use to control about 2 meters of your average 5050 RGBW 24v LED strip. It should consume about 35 watts in all, so at about 370mA per channel it shouldn't be too monstrous to handle, I think.

All the LED drivers I have found so far require big MOSFETs with heatsinks, so I'm wondering how it is possible that all these cheap chinese wifi controllers can handle it in such a small and relatively low temperature package? Isn't it possible to make something like that? Suggestions i've had were using the IRL540NPBF 1 N which can do a whopping 140w on its own, which seems excessive to me.

Does anyone know of a component I could use on a typical 2.54mm board to make a nice little PWM controlled 4 channel LED driver?


I remember using the BS170 for driving "small" LED-strings.

  • N-Channel
  • 500mA Continuous Drain Current (Id)
  • 60V Drain-Source voltage (Vds)
  • 2.1V Threshold Voltage (Vgs), which is ideal for arduino's 5V outputs
  • TO-92 package, you can bend the pins to fit a breadboard

See BS170 LED arduino example for an example on how to use the BS170

  • 1
    \$\begingroup\$ A solution AND an example on how to apply it. As good as it gets, thank you! \$\endgroup\$ – Sokonomi Nov 13 '19 at 10:29
  • \$\begingroup\$ I'm going to have to come back to you on this one i'm afraid;Are you sure these can grunt about 9 watts of power? Im terrible at reading data sheets, but it states 'Total Power : 830 mW'. \$\endgroup\$ – Sokonomi Nov 13 '19 at 11:43
  • \$\begingroup\$ Correct me if I'm wrong but I believe that to be the power dissipation of the BS170 itself: check: onsemi.com/pub/Collateral/BS170-D.PDF , this power is much lower than the power trough the LED strip because of the lower voltage. Hope this helps \$\endgroup\$ – Ruben van Leeuwen Nov 13 '19 at 12:03
  • \$\begingroup\$ Aha! That makes a lot more sense than the sheet I was reading, thank you. So at 24v it should be good for about 12 watts. So it should be alright when I push for 9 watts. I'm trying to gleam the drain current to temperature correlation, but im having difficulties. Do you think it would get hot during operation? \$\endgroup\$ – Sokonomi Nov 13 '19 at 17:13
  • \$\begingroup\$ Yes it can get hot and you do need to keep an eye on the drain-source-voltage, multiply it with the total current running trough the BS170 and keep that power-level below 830mW \$\endgroup\$ – Ruben van Leeuwen Nov 14 '19 at 6:59

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