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Topic: esp32 and 2.4" SPI TFT ili9341 led input 5v (Read 189 times) previous topic - next topic

europer

Hi,
perhaps in the forum but cant find it.

The 2.4" SPI TFT ili9341 is a nice display and work perfect with my different esp32 (wemos lolin 32 light and ttgo T8 V1.7) so no problems.

The display is working VCC = 3.3V and LED to controll the light (and also to dim the display).
As I was testing a bit around I did see that if I use 5V (what you can also use expample a arduino) the brightness of the display is lot better (sunny days).

So here my question(s):

1. If we use a tranistor/mosfet to controll a voltage of 5v (instead of 3.3v) and the adjustmet of britness through the output signal of esp32 (for this I use this code at given time with 3.3v https://randomnerdtutorials.com/esp32-pwm-arduino-ide/)
2. somebody done this and how would the wiring look like? (see my attachment, VCC=5V and LED comes from ESP32 with max 3.3V)

Last question the VCC for the display (1st pin on the TFT) can be between 3.3 and 5V (my model can both) do this have any impact of the point 1 and 2.. Lets say I can use 5V on LED and controll it over a transitor with max 3.3V but the 1st pin of the display (VCC) with 3.3V. Why do I want it to keep it like this, this to controll it over the MC if I need to turn of the display or not.

Thanks


david_prentice

I do not believe your schematic.   Most displays have more components on the pcb.

Post a link to the actual screen that you have bought.  e.g. Ebay sale page

Or post a photo of the pcb on your desk.

David.

europer

Hi David,

the schematic is correct, is not the pcb view but the schematic view.
but here the link to the same I have:

https://www.amazon.de/Zoll-240x320-Serielles-Anschlussmodul-ILI9341/dp/B0749NHRV4/ref=sr_1_fkmr1_2?__mk_de_DE=%C3%85M%C3%85%C5%BD%C3%95%C3%91&keywords=tft+2.4+spi+though&qid=1582899260&sr=8-2-fkmr1

BR
Per

david_prentice

#3
Feb 28, 2020, 04:32 pm Last Edit: Feb 28, 2020, 04:42 pm by david_prentice
Your Red ILI9341 SPI display requires 3.3V logic signals.  e.g. from ESP32 or ESP8266.

It has an on-board regulator i1 which means you can connect VCC pin to 5V and the regulator provides 3.3V to the display controller.
You can bypass the regulator by shorting J1 i.e. if you only have 3.3V

This particular board does not have a XPT2046 Touch controller mounted U2.
This particular board does not have a transistor to switch the backlight via the LED pin.

So yes,  you can supply the LED pin with 5V if you like via a limiting resistor e.g. 22R.
Or via a PNP transistor and 22R.

I do not advise your NPN "emitter follower" circuit.   Especially with a crap transistor like 2N2222.
Choose a PNP with hFE > 100 @ 100mA collector current.   It will still need >1mA base current.

The controller requires 3.3V logic.
The backlight draws 50mA - 100mA.   Make sure that the resistor is suitable value for 5V.   (or smaller value for 3.3V)

David.


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