I have a circuit that was running great when hooked up to my computer via USB.
I have a piezo, 5 led lights, and the LCD screen.
I have just attached the battery pack (4 AAs) to the vin and gnd inputs on the arduino uno board.
Everything is working except for the contrast on the LCD screen. I can still see the characters but they are very faint and darker than the back light. How can I get the LCD contrast back to what it was when hooked up to the computer? The image is with the board off as I couldn't get an image to show the screen contrast.
I am just learning arduino so detailed explanations would be helpful!
Thanks for the photo.
I can't see the batteries, are they 1.5V AA batteries ?
Four times 1.5 = 6V.
The voltage regulator makes about 5V of that 6V.
However, when the batteries are a little low, or are NiMH batteries, the voltage regulator on the Arduino Uno can no longer make 5V. It may be 4.5V.
Those LCD displays need 5V. They are the first to stop working with a lower voltage. That's just how it is. Nothing you can do about it. I assume you tried adjusting the contrast potentionmeter for the LCD ? You could use a battery pack of 7.2V. Or a 12V battery pack with a DC-DC converter.
Do you have a multimeter ? Can you measure the voltage of the 5V pin of the Arduino ?
P.S.: Welcome to the forum. I noticed that no one answered your first post about not able to communicate with the Arduino board. Sorry for that. Did you solve it ? or did you buy a new board ?
What Peter_n said is essentially correct but he stopped a little short.
The contrast voltage specification is referenced not to GND as we tend to measure it but to the supply voltage, typically around -4.7 volts.
This means that if the supply voltage is 5.0 volts you need 5.0 - 4.7 = 0.3 v with respect to GND.
It also means that if the supply voltage is 4.5 volts you need 4.5 - 4.7 = -0.2 v with respect to GND. You will need a second power supply to achieve this.
