Hi,
My LCD 16x2 12C screen is too bright and i want to adjust it's contrast. However it doesn't have the 12C module backpack so no blue built in potentiometer. What connections who i need to adjust the contrast on the LCD to a potentiometer
Please post the datasheet for exactly that LCD.
Posting a close picture of the rear side might help us.
Thanks. Sadly I can't identify a point of attack.
My guess is that You need to cut a strip and instal a resistor across the cut.
But where do do it?
You need the datasheet or some kind of manual.
No worries i will try to figure it out thanks
If You find technical information, please post it.
You could try this: remove the solder blob between Vo and Vdd. Hook a 10K pot up to Vdd and Vss with its wiper to Vo as normal.
that works! thanks however after slight movement of the breadboard or lcd the contrast changes back to being too bright or starts showing random words and characters is this a wiring problem? i have connected the LCD to vcc, gnd, sda, and scl.
The backlight led is brought out to a seperate pin on the LCD module, you can PWM that to control brightness. That is assuming you are not using a back pack. If you use a back pack there is a jumper that turns on the back light, that could be PWM controlled but I do not have a circuit for it.
I've not seen that LCD1602 design before where it appears there is an on-board pcf8574 I2C port expander. Can you post a link to the vendor site. I guess that the 3 holes in triangular formation at the top edge form a footprint for the missing contrast potentiometer.
EDIT
I found one :
Freenove I2C LCD 1602 2004 Module IIC TWI Compatible with Arduino Raspberry Pi
The documentation says this:
So it does appear that somehow they have eliminated the need for a contrast potentiometer which would normally bias pin V0. Unfortunately, there does not appear to be a schematic so it is not easy to see what they have done.
If the screen is simply too bright, as opposed to a contrast problem, then put a resistor (say 100R) in series with backlight LED. It does appear anyway that R9 (100R) controls the backlight brightness:
Thank you everyone, i have adjusted the contrast by connecting the pot it to the three pins in a triangle with the wiper in the pin on the right. i have also tried the VDD and VSS with the wiper in V0 and that works as well
Are you sure? Usually the wiper is the middle pin. If you get that wrong there is a risk that you short VDD and VSS (the power rails) if you turn the potentiometer to an extreme position.
Basically, yes. The breadboard connections are poor enough so that contact resistance plays a significant part. You may find that soldered connections are more dependable in this regard.
However, you'll still run into a problem if the power supply on your board fluctuates. There are ways around this, such as maintaining a constant current through the V0 pin - however, the easy way out of this is to just ensure a stable power supply to the display in your final project.
This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.