ESP32 project hardware power issues

Projects General Guidance
23

From the datasheet: Rds(on) at Vgs of 2.5V is only 5.2mΩ.
Your LED current is a little over 1A, so let's use 2A

Power: P=I x I x R.
I = 2A and R = 5.2mΩ
P=2 x 2 x 0.0052 = 20.8mW
However at 3.3V the Rds(on) will be even smaller so the power dissipation will be even less.
I use the Rds(on) at 2.5V because it's not specified at 3.3V, but it has to be less, so using 5.2 is more than safe for doing the power calculation.

I found a resistance of 1.25 Ohms at 70°C for the IRLZ34N

I have no idea where you got that number.

What other microcontroller or board would you use when not using WiFi?

Pro mini is small otherwise the nano.

24

If you use a 5V microcontroller you could use the IRLZ34 at 2A no problem.

25

okay then at least my calculations were right, even though based on wrong numbers apparently.

Read it from a temperature-vs-resistance diagram in the datasheet, but yeah now I see where I should've looked.

I had a look at both. While being smaller and having less features that would be left unused anyway compared to an ESP, they still are more expensive. I went and ordered an ESP32-C6 Mini. Let's see how that goes.

I can't follow you on this one, is the IRLZ34N more efficient when being controlled with a voltage of 0 up to 5V? Where's the difference if I provide a gate voltage of 3.3V - wouldn't this change only be effective when actually driving the lights at full brightness? And even then, the IRLZ34N currently already provides the full 12V when being driven with 3.3V - what else would it do when being driven with 5V? Might be some very basic questions here, my apologies already :slight_smile:

26

Let me ask you this:
For the IRLZ34, what is the maximum Rds(on) with Vgs=3.3V?

27

aah I see, the datasheet I have only has Rds(on) values for Vgs of 4V and 5V, but they already show what you were saying:

  • Rds(on)=0.06 Ohms for Vgs=4V
  • Rds(on)=0.046 Ohms for Vgs=5V
28

and there is not enough information in the datasheet to even make a good guess as to what a typical value might be at 3.3V.

You should have no problems with the IRLR6225

29

Yes, the datasheet isn't very helpful in this regard.

I'll order some and try them. Thank you very much for your answers!