Raspberry Pi Forums

Hi,
I am creating a temperature monitoring pi using a Pi Zero W and displaying the temperature as a colour on the SMD5050 LED Strip using the IRLZ34N as per https://dordnung.de/raspberrypi-ledstrip/

I am just working with one colour at the moment (RED) while testing etc.

I have it all working but the red LEDs are very dim even when using I swapped out the IRLZ34N for others but still dim. ie it made no difference.

I then noticed once I had turned off the pi and pulled the jumper leads off the pi I then accidentally touched the jumper lead to the gate of the IRLZ34N the LEDs came on and became fully bright.
So I know the IRLZ34N are working correctly but anyone know why they are dim when being driven by the Pi Zero?

thanks

Hi, may I suggest you're using a logic level FET, but driving it from 3.3 not 5.
Several drivers handle 3.3 in and 5+ out. G.H. <<<)))

Are you saying I should be using a FET or I should not being using a FET, not sure what you mean.

The IRLZ34N is a FET, it's a 3.3v max gate voltage MOSFET

The Zero GPIO do not work at 5V

CustomSarge wrote: ↑

Mon Jun 22, 2020 11:52 pm

Hi, may I suggest you're using a logic level FET, but driving it from 3.3 not 5.

SniffTheGLove wrote: ↑

Wed Jun 24, 2020 6:09 pm

The IRLZ34N is a FET, it's a 3.3v max gate voltage MOSFET

Not quite true.
Its max gate voltage is 16v - it'll survive if you give it that much - but its gate threshold voltage is typically between 1v and 2v.
That means it will start to turn on at that sort of voltage, but, depending on how much current you want it to handle, you may need to drive it harder - give its gate a higher voltage.

Thanks,

How do I give it more voltage when the GPIO only provides 3.28v? Would I need yet another MOSFET or transistor inbetween the GPIO and the IRLZ34N to raise the voltage.

I think your best bet would be what's sold as a logic level converter.
They're generally meant to translate 3v3 signals to 5v, but would work just as well translating to 12v
And the advantage for is you can get them as four on one board - one for each colour and one spare! Just read 12v instead of 5v - the 2N7000 can handle 12v with no problem.
The gate of your IRLZ34 takes very little power, so the 10k pull-up resistor is adequate, and will drive the hexfet fully on.