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Author Topic: Problem with my 3.3V LCD screen 1602 contrast not working  (Read 441 times)
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Hi there! First of all, i'm french so my english is sometimes really bad.

So, i have problem with my new blue and withe/ 3.3v lcd

I cant get contrast working on the lcd, i try everything (10k pot,5K pot and a bunch of resistor)



  Here is the wiring i made.

Before i knew it was a 3.3V screen i put it on 5V is this can be the problem? Did i fried it?


Thx.
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blue and "white".
What makes you think it is a 3.3V display ?
That would be unusual for a 1602 display.
Can you give us the link from where you bought it ?
Do you have multimeter for taking measurements ?
Can you measure the voltage on the contrast pin ?
What voltage do you think it should be to see the text ?
Why are there no other wires connected other than
backlight ,power and contrast ?

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its this one...
http://www.wvshare.com/product/LCD1602-3.3V-blue.htm

i follow this tutorial... and i dont see white ''square'' for adjusting contrast.
http://www.dreamdealer.nl/tutorials/connecting_a_1602a_lcd_display_and_a_light_sensor_to_arduino_uno.html

and yes i have a multimeter

Thanks for the fast reply
« Last Edit: January 28, 2014, 10:34:11 pm by Gablussier » Logged

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Why are there no other wires connected other than
backlight ,power and contrast ?

Because you don't need any connections to the Arduino to establish the fact that the contrast is working.  If you can't get the contrast working at this point there is no sense in connecting any data or control signals.

Don
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... and yes i have a multimeter

There is the possibility that your backlight needs an external current limiting resistor and without one it could be drawing enough current to cause the 3.3v regulator to shut down.  Use your multimeter to make sure that you are still getting 3.3v with your circuit connected as shown in your photograph.

If that is OK then make sure that you can adjust the contrast voltage from 3.3v to 0v.


Don
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I get 3.29 on pin A & k (15-16) backlight

And i get 3.30 one pole on the ground pot, and the other on the  wiper wich is connect to the pin 3 (contrast) i've got fully control.

Backlight is working but i dont the withe square.
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Got it. You don't see the pixels (white dot-matrix).
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yup
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Before i knew it was a 3.3V screen i put it on 5V is this can be the problem? Did I fried it?

Definitely a possibility.  This clearly is a 3.3V unit, identified by the existence of "U3" on the back along with C1, C2 and J3.

R8 is the correct value for 3.3V operation - I cannot quite see what its value is on the illustration.  R9 is zero ohms.

Remember that the correct setting of the contrast potentiometer is close to the "ground" end.

Connecting only pins 1, 2, 3, 15 and 16 is indeed the correct approach at this point.  If you cannot get the first row of blocks to show as you turn the potentiometer down to the ground end, that looks really bad.  It may be illustrative to see what is the maximum voltage you can find with the meter with the potentiometer turned to ground and measuring across the (various) ends of R1 and R5 (i.e., one probe on R3 and one on R5).

Should be nearly 5V (with 3.3V supply)!
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And i get 3.30 one pole on the ground pot, and the other on the  wiper wich is connect to the pin 3 (contrast) i've got fully control.
You should get 3.3v with the pot at one extreme but you should also get 0v with it at the other extreme.  As Paul said you will not get the row of blocks until the contrast voltage is at or near 0v.

Don
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Nothing happen smiley-sad my pot works good...
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