# Battery powered LCD and ATmega328

Hi,

The goal of my project is to display a series of images from an SD card on a tft lcd screen using an ATmega328-PU on a breadboard , all powered with a battery.

I’ve successfully loaded my code onto the ATmega328 and everything works fine—if my power source is the Arduino board’s 5V pin. (If it is useful, I’ve included an image of it working with the 5v pin.) I can’t get it to work with a 9v battery. I know very, very little about electricity and electronics, but I’ve tried everything I can think of:

1. ATmega328 and LCD both powered through one 9V battery.
2. ATmega328 and LCD both powered through 4.5V (one 9V battery voltage divided through 1kΩ resistors).
3. ATmega328 powered through Arduino; LCD powered through one 9V battery.
4. ATmega328 powered through Arduino; LCD powered through 4.5V or 3.2V (one 9V battery voltage divided through 1kΩ resistors or 566 Ω & 1kΩ resistors respectively).
5. LCD powered through Arduino; ATmega328 powered 4.5V or 3.2V (9V battery voltage divided through 1kΩ resistors or 566 Ω & 1kΩ resistors respectively).

I’m using Adafruit’s 2.8” Capacitive TFT LCD. The datasheet can be downloaded from here. Direct download of the datasheet pdf is here. As far as I understand, the max input voltage is 4.9, minimum is 1.65V; it looks like max supply current is 80mA. For reference, the ATmega328 datasheet is here. As far as I understand, the max input voltage is 5.5, minimum is 1.8V; and I’ve seen max draw up to 21mA and 81mW.

If I follow, a 9V battery, at 450mAh, divided between the two should be supplying the correct voltage to run both the screen and chip, right? I really have no idea.

I don’t have any tools to directly measure voltage, current, etc.

Any help is appreciated.

``````9v battery
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You mean one of those little square things like goes in the smoke detector? That can't support the current needs you have.

PS. Don't ever try to split supply voltage with a divider. The things you are supplying are also drawing different amounts of current so your divider calculations will all be way off. As current draw changes on devices so will their supply voltages. Not a good thing.

I should also clarify that I am able to turn on the screen, and it is back lit to a seemingly typical level. I just can’t get the setup color to display or the photos to begin.