Display takes about 400mA. It's too much current and brightness!
Have anybody success with modifying shield to allow backlight control (or kill 50% of leds)?
Image attached.
In the old days Mcufriend displays had an AMS117-3.3 LDO regulator on the pcb.
This was fed from the 5V pin. The regulated 3.3V went to the BL pin on the TFT Panel Ribbon. A resistor-pack limited the backlight current or they relied on the ribbon components.
The new pcbs omit the LDO regulator. And do not seem to have any series resistor to replace it.
You will have to identify the trace that goes from 5V to the BL on the ribbon. Cut the trace and put a 22R resistor across the gap.
Yes, some of these shields take 400mA and get VERY warm. My new Nucleo-144 board monitors the USB current.
It would cost Mcufriend very little to mount a resistor pack with some solder-bridge pads. e.g. 4x100R pack would give a choice of 50R, 33R, 25R
Hey-ho. Mcufriend could stick a paper label on each pcb to say which controller was mounted. They could use proper LVC245 instead of HC245 buffers.
David.
I’m not sure who designed these mcufriend tft lcd’s you sell , but they are a BAD really CRAP design - with the backlight LED's connected directly to the +3.3V bus - WITH NO CURRENT LIMITING RESISTOR & they draw over 400mA, overloading both the Arduino Mega 5v & 3.3V regulators – and definitely limiting the backlight LED life, as they run at 40-50C.
I have managed to drop the current by cutting the 3.3V trace to the TFT - pics show details
I don't sell anything. I have no connection with mcufriend.com at all.
Yes, there are several things that are WRONG with the shields. Especially the current pcbs without AMS1117.
I have no idea where your "22R" resistor is going.
I am horrified if the backlight is being fed from the Arduino 3.3V pin. This pin is not designed for high current.
I have never really looked at these "new" pcbs. There would be no problem with feeding the backlight from the 5V pin via a sensible series resistor. Bear in mind that the resistor must dissipate up to 250mW. Backlights might need 40mA - 100mA. Depending on panel size.
David.