Convert 5V TFT shield to 3.3V shield - Confirm understanding

Hi,

Could a TFT hardware expert please help me?

I just received a Mega TFT shield as shown in attached and it works on a Mega with a 5V TFT.

So, it feeds 5V on the VCC pin (pin 2) and 3.3V on the LED_A pin (pin 19).

There is a little jumper below the regulator and if I short it , the only change I noticed is 5V on the LED_A pin which make my 5V TFT brighter

From previous (bad) experience I know my other TFT needs 3.3V on VCC and LED_A pins.

My question is…

If I disconnect pin 2 ( break it up) and feed 3.3V to the pin 2 from the regulator, will my TFT work with my 3.3V TFT. I think the answer is YES - please confirm?

I am assuming (correctly I hope) all other pins are running at 3.3V for all types of TFT.

Thanks

I don't know about the display or shield you talking about, but if you are putting together 3.3V and 5V systems, you need to handle the outputs too. Some 3V devices break if there is 5 volts on any pin.

It seems in this forum resistors are used to lower the voltage, kind of. But you can also use level shifter ICs to do that.

Not much but I hope this helps.

Yes your proposal will work. Pin 2 for both of my displays is 3.3V. You should have got a CTE shield while you were ordering your CTE TFT ;) :P. The CTE Shield has more jumpers than you can shake a stick at..... You can select 5V or 3.3V for LED_A, VCC and signal input voltage independently :D.

Regards,

Graham

Hi Graham,

Thanks - I will try it this week and report back. My second question ( sorry it was unclear ) was if I have Pin2 supplied with 3.3V and LED_A too which I know is correct for my TFT, are all the other pins always compatible i.e. always 3.3V compliant regardless of which shield I have?

Please see PS's to not 'bore' others :) :)

Thanks

PS1 - I did get a CTE shield as well, but before my conversion to CTE by you, I had ordered some 'cheap' parts which is why I am going back to experiment with rather than abandon them. :) :) But I am being ultra cautious before plugging a working TFT in these shields.

PS2 - Regarding recent delay, I have now discovered 'notifications' and turned them on. All are off by default. :confused: :confused: :confused:

Yes all the other pins are 3.3V, you are safe once you modified pin 2.

Graham

Great... thanks.

I will try in next 48 hours and report. Its only an experiment.. I wont rely on these long term but useful to have a back-up when waiting for 4 weeks for delivery

Hi Graham,

The mod worked !!! Please see attached photo.

Many thanks for the help

Instructions if anyone needs it at their own risk…

  1. I cut away the plastic around pin 2 of my shield to reveal the female metal pin inside (this delivers the 5 Volts)

  2. Then pulled out the female pin while desoldering it at the other end.

  3. I further cut away more plastic around pin 2 to make space for prototyping cable.

  4. Took a standard male to female prototyping cable and cut off the male end to leave the female end and about 7 cm of cable.

  5. I soldered the cut end to Pin 19 (LED_A) which LUCKILY for me was connected to the 3.3V regulator.

  6. I slightly splayed out PIN two of my TFT, then plugged it into shield. Then finally plugged in the external female pin carrying 3.3V.

  7. Then powered up - and it worked instantly ( I had already preloaded a UTFT example with correct device ID).

Great! And of course, should you ever need to, you can easily change it back to 5V. :D

Graham