SparkFun Forums

[Octagon26]

Hello, I recently purchased a Serial Enabled 16x2 LCD - White on Black 5V

sku: LCD-09395

and got it working with my Arduino relatively quickly. Had a few problems with the text wrapping, but that is a separate issue.

(1) PROBLEM: when the Arduino gets its power from my Mac via USB, the LCD displays the splash screen and then writes the text from my arduino script just fine.

BUT: when i connect the arduino to a verified 5v external power supply, the LCD turns "on" but the characters that it displays are incredibly dim, at fist i though that it was not working, but will all other light off, i can barely make out that the LCD is still working.

Any ideas what i have to adjust? It should be getting 5v, because it is connected to the 5v pin of the arduino, and the arduino is getting 5v from the power adapter.

thanks for any suggestions!

(2) The other issue is that if i feed the LCD a serial.print("some text") command and the "some text" string is longer than one line on the LCD, it drops a character or two when it auto-wraps to line two.

-Octagon26

[lehmanna]

What type of Arduino do you have? Some of them have an on-board voltage regulator and hence "need" more than 5V power supply when the power jack is used. "Need" is maybe a bit misleading here, since the microcontroller itself can run at really low voltages, nevertheless a regulator would drop the voltage just too much for the 5V outlet.

[Octagon26]

I have an Arduino Decimila and i just checked the summary:

Input Voltage (recommended) 7-12 V
Input Voltage (limits) 6-20 V


Indeed it looks like my 5v power supply is probably not enough Voltage. I had assumed that because the operating voltage is 5v, i would need a 5v power supply.

I guess it makes sense to read the documentation.

THanks for your reply!

-Octagon26

[lehmanna]

You're welcome.

BTW, two serially connected lithium polymer cells would fit your needs just perfectly. As an alternative, you can power the Arduino via its USB port. Although the USB port supplies only 5V, the voltage regulator is "circumvented" if power comes from the USB connector. However, you have to pay attention since some USB hosts provide only less than 5V (IMHO as little as 4V is allowed by the USB spec.).

[puffyfish]

You need to set the gamma on the LCD. It can be done with a resistor or potentiometer.