Make ILI9341 dispaly brighter by changing resistor value??

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Matadormac

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Hello the list.
I have completed my portable meter project and put in a case. Field testing shows that the ILI9341 wired as suggested in the PJRC store page and using a 100 ohm resistor from VCC to LED is bright enough in low light indoor situations but unreadable in higher light situations especially out of doors (even in shade). I would be happy for a display bright enough to readily read in all indoor lighting situations and just possibly in the shade out of doors but this last is currently not a great need.

In posts on this list I see some people have "brightened" their ILI9341 display by using a lower resistance value resistor. bboyes has used a 5 ohms resistor while FrankB has used a 10 ohm resistor from VCC to LED.

The sensors I am using are low power consumption and only on upon demand, battery life is not a great issue at this time.

Are there any reliability issues or other issues I should be aware of before trying these lower value resistors with my project? Oh, yes, Teensy 3.2 is the micro-controller I am using. The ILI9341 display is wired to the Teensy 3.2 3.3V output.

Thoughts and advice?

Best
 
I wired the LED through the 100 ohm resistor to the Vin (3.6 to 6.0 volts) terminal and the resulting display brightness if very much better. I will field test today. If the display needs to be more readable in areas with more ambient light I will change the display background color(s).

Question: If I want to make the display lighter still, can I change the 100 ohm resistor to something like a 50 or even a 25 without damaging the display? It would be getting the voltage from the Vin terminal which is being fed 5.5 V from a regulated battery power source.

Thank you
 
The 100Ohm resistor is a current limiting resistor for the LED on the display. I believe
Changing this will only blow the LED. It won't effect the screen brightness

The device will accept a maximum of 5.5V on Vin. This is your theoretical maximum without over driving and almost certainly breaking the display
 
Another way is to run a pwm to a fet and power the backlight with the fet, adjusting the duty cycle to control the brightness. Some of the Adafruit screens use a Fet to allow controlling the led with a digital or pwm signal.
 
Hm, the displays i have all have a current-limiting resistor on board. I run them with 5 v and additional 10 ohm(+5..8 ohm from an old fet) for weeks now ( some hours per day).
But you should check the current of course.
 
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