ILI9341 LCD panel gets very toasty

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CharmingBrew

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Hi all, I just received my LCD board from PJRC.com and hooked it up with a Teensy 3.1 and loaded some test code.

It seems to be working great, but it gets very hot to the left and right of the flex cable on the panel. I measured 200 F with a thermistor probe on my multimeter.

I think it's related to the backlight. I currently have it hooked up with 100 ohm resistor and 5 volts DC.

This doesn't seem normal and I don't want to damage the panel. Any suggestions?
 
It should not get noticeably hot.

Perhaps double check that resistor and connection to the LED pin, or post a photo of your wiring?
 
Hi,

Paul it seems your last delivered 2.2' displays have a different circuitry for the back light from shown on your web site.
Adding a 100 Ohm resistor has no effect on LED, because this pin of display is connected via 1kohm to a basis of a transistor for swiching back light LED on/off to power. So with this you can use one pin (of teensy) for direct PWM the back light.

May be this causes higher current and temperature (especially if LDO on display is shorten by solderable jumper).

Best regards
 
The back-lights in the 2.8" ILI9341 with Touch are rated at 80mA(20mAx4) @ 3.2V. The 2.2" version is probably similar.
larry or CharmingBrew, could either of you post a picture. If there is a transistor driving the LED now its most likely hooked to the onboard 3.3V LDO of the screen.
 
The back-lights in the 2.8" ILI9341 with Touch are rated at 80mA(20mAx4) @ 3.2V. The 2.2" version is probably similar.
larry or CharmingBrew, could either of you post a picture. If there is a transistor driving the LED now its most likely hooked to the onboard 3.3V LDO of the screen.

It is like you discribed. Foto attached.

IMG_1297.jpg
 
Looks like an N-channel FET, the source is tied to Gnd. So the led cathode goes to the Fet drain.
larry with a DMM can you confirm if the LED pin goes to R4. If it does can you tie led pin to gnd, then measure the current when you apply 5V to VCC (Backlight should stay off), then tie it high and measure the current again. The LED's should not use more then 80mA.
 
Looks like an N-channel FET, the source is tied to Gnd. So the led cathode goes to the Fet drain.
larry with a DMM can you confirm if the LED pin goes to R4. If it does can you tie led pin to gnd, then measure the current when you apply 5V to VCC (Backlight should stay off), then tie it high and measure the current again. The LED's should not use more then 80mA.

Yes, R4 goes to LED pin. I have disassembled one display.
Your suggestion for measurement should work as discribed. But bear in mind the display backlight differs from vendor to vendor, sometimes there are 3 LEDs and sometimes 4 LEDs for backlight. So a current between 60 mA and 85 mA if LED pin is high and VCC between 3.6 and 6 Volt should be fine.
 
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