can the 16x2 LCD pin RS & Enable connect to other than pin11 & 12?

My question is can these 2 pins from LCD connect to any of the Arduino pin other than pin11 & 12?
As i move from pin 11 & 12 to Pin 6 & 7 of Arduino, the LCD screen freaking a bit when i turn on the 3 x led light bulb.
Note the LCD pin 15 or Led+ is power with Arduino broad 3.3V togrther with 3 x led light bulb..

below are some infor extract from Arduino LiquidCrystal.

the usual way

  • LCD RS pin to digital pin 12
  • LCD Enable pin to digital pin 11

A register select (RS) pin that controls where in the LCD's memory you're writing data to. You can select either the data register, which holds what goes on the screen, or an instruction register, which is where the LCD's controller looks for instructions on what to do next.

An Enable pin that enables writing to the registers.

Hi and welcome.

How much current do you think you can draw from the on board 3.3. volts ?
And what board is that ?

My question is can these 2 pins from LCD connect to any of the Arduino pin other than pin11 & 12?

The answer to this question is yes. Any Arduino I/O pin can be used to drive any of the LCD data or control lines. The numbers in the constructor are used to tell the library which Arduino pin is connected to which LCD pin.

The documentation is not easy to find.

It would all be much clearer even without finding the documentation if a few comments were added to the tutorial example:

//LiquidCrystal lcd(RS, E, D4, D5, D6, D7);
LiquidCrystal lcd(7, 8, 9, 10, 11, 12);      // put your pin numbers here

Don

MAS3:
Hi and welcome.

How much current do you think you can draw from the on board 3.3. volts ?
And what board is that ?

Hi MAS3,
DC Current for 3.3V Pin 50 mA from the summary here https://www.arduino.cc/en/Main/ArduinoBoardUno.
Probably the current not enough for LCD & 3 x leds to run together.

Or i can connect to 5V for LCD & 3.3V for led bulb.
from datasheet indicate LCD Backlight VCC (5V) for Led+ pin-15.

But for 5v need a resistor. i know online there a lot of source saying the resistor value. How they derive the resistor value?

floresta:
The answer to this question is yes. Any Arduino I/O pin can be used to drive any of the LCD data or control lines. The numbers in the constructor are used to tell the library which Arduino pin is connected to which LCD pin.

The documentation is not easy to find.

It would all be much clearer even without finding the documentation if a few comments were added to the tutorial example:

//LiquidCrystal lcd(RS, E, D4, D5, D6, D7);

LiquidCrystal lcd(7, 8, 9, 10, 11, 12);      // put your pin numbers here




Don

Hi Don,
i didnt know of this sequence after you & one of my friend highlight to me.

LiquidCrystal(rs, enable, d4, d5, d6, d7) .

And from MAS3 the 3.3V with 50ma is not enough to support both hardware.
Cos when i make 3x Led bulbs to blink, the LCD contract also blink with the Led bub.

Some infor i found for sharing.

The total voltage drop across these LEDs is typically 4.2 V and the recommended current through the LEDs is 120 mA. You should use a current limiting resistor RLIMIT as shown above where:

RLIMIT = (VBACKLIGHT – 4.2V) / 0.12A
VBACKLIGHT = 5V

ahbee87844:
Some infor i found for sharing.

The total voltage drop across these LEDs is typically 4.2 V and the recommended current through the LEDs is 120 mA.

That "information" is quite useless without the complete specification of the LCD display.

Most of those available on eBay contain a resistor "R8" which is marked "101" - 100 ohms - and which already limits the LED backlight current to 20 mA without any external resistor and means you can control it directly with an Arduino pin. Most also have a resistor "R9" which is "0" - zero ohms. The two might possibly be exchanged but if either is "101" then you do not need an additional resistor.

Hi Paul.

I think you missed him telling about the separate "3 LED bulbs".
I read that as 3 additional LEDs, next to the display's backlight LED(s).
That's why i asked this question, hoping to have OP check the total current drawn from the 3.3 volts.

I don't think I missed anything!

I think it has adequately been pointed out that you do not use the 3.3V supply from the Arduino for powering the backlight or additional LED indicators - that is not what it is suitable for.

If he proposes to use other than a "standard" (commonly available, eBay or such) 5V LCD display to which I referred, then he will need to specify it with a link to its specification and properly explain - with a circuit diagram - how he proposes to connect this all together.

Hi all,
Thank MAS3 & Paul for the knowledge sharing here. It did trigger me to look at for 3.3v pin can support how much current.

It a circuit for the voice command to control 3x leds bulb, & LCD will display which bulb light up (SEE circuit)

Actually i am controlling the 3 x LEDs bulb to power-up individual through the Condenser Microphone.

My mistake here: should have include circuit diagram to show you all the full view.
I make a mistake on the connection
3.3V is use to power up the LED pin15+ & Condenser Microphone 1.5V & 0.5ma.

3 x LED bulbs(red , yellow & green).
operating voltage for above 1 x LED bulb is 1.7V & current 15ma
Resistors (220ohm) = (5v-1.7v)/15ma

LCD model: 1602A QAPASS

From the spec indicate 5V for the lcd operating voltage.
But i cant confirm is there a built in resistor for the pin-15 led+ so that 5v from Arduino can be connect to it.
That y i connect pin-15 led+ to arduino 3.3v

Below is the circuit diagram.

But i cant confirm is there a built in resistor for the pin-15 led+ so that 5v from Arduino can be connect to it.
That y i connect pin-15 led+ to arduino 3.3v

Look at reply #6 where Paul pointed out that "Most of those available on eBay contain a resistor "R8" which is marked "101" - 100 ohms - and which already limits the LED backlight current to 20 mA without any external resistor "

Your display fits that description exactly - where R8 appears near the top left of the pc board and is marked 101 meaning '10 followed by 1 zero' or 100 ohms.

The 100 ohm value was chosen to give the correct current when driven from 5 volts. When you drive it from a 3.3 volt supply the backlight will be dimmer at best and it may not work at all.

Don