I am about to start a project that requires 2 LCD screens from a single Uno. It needs to show the same data on both. Can I simply run both LCD's (Normal or I2C) with all connections in parallel or will I need to use two Arduinos and/or two displays separately from same Uno?
Sorry if this has been asked before. I couldn't find answers based on the same data being displayed.
For context, I am fitting a camper trailer with water tanks and using flow meters to show tank volumes. I would like to show the tank volumes on the fill side as well as the tap/draw side.
I2C for sure; you just need to give each module its own address and update each module individually.
I do not immediately see a reason (looking at the library and the wiring) why the 'normal' ones can't be connected in parallel but I might be mistaken.
Two displays will draw double the current; I would advise that you do not power them from the Uno's 5V pin.
You can definitely run several character mode LCD's in parallel using the 'normal' method. Each display requires it's own 'E' pin and the others are all connected in parallel.
The links to the photos are broken but I can dig them up and repost them if you need to see the proof!
Note that these examples have different data displayed on each LCD but of course you can send the same data to all of them as you indicate you want to do.
You could try paralleling the 'E' lines to send the same data to all displays at once and see if it works but I have never tried that.
What has not been specified is what these displays are.
I will presume the common "1602" LCD modules. The backlight LEDs draw about 24 mA each, so one can be controlled by an Arduino pin (UNO - which is a poor choice - or Nano, using an ATmega328). You would need some other arrangement for switching the backlight of two displays.
If you use them with the I²C backpacks, then the two displays are separate, you need two instances of the code to drive them even with the same data. But the backpack includes the control for the backlight.
You do not switch the displays off, only the backlight.
The displays I used a decade ago were already several decades old. The backlights (if they had any) would have been electroluminescent and they would have been connected to the two tabs at the right end of the module.
Thanks for the update and your help. Nice set up there btw
I have ordered a nano and 2x I2C displays. TinkerCad allows both to run simultaneously but I think that might be a bug rather than true representation. We will see soon enough.
