Arduino to Maxim 7219, 296 LEDs, Battery powered

Thread Starter


Joined Feb 26, 2011
Hello All About Circuits forum,

It has taken two years from project conception to completion.
A lot has been learned. A lot has been gained from this forum for
which I am grateful.

The project is to control about 300 LEDs with the Arduino Uno
and the Maxim 7219.

This is an animated GIF of the first four characters of the total
of eight characters displayed.

This is a video of the completed display.
Video of completed project.
(Can't imbed the video for some reason.)

One of bumps in the project road was power.
The specs on the LEDs says 'Current:20 mA'
LED specs
I think that means that 20 mA is the max the LED can draw.
So using that as the current, 300 LEDs draw
6000 mA or 6 amps. A standard D-size carbon-zinc battery
has an amp hour capacity of 4.5. Each battery
is 1.5 volts so four batteries provides 6 volts
and 18 amp hours.

So here is the question. Right now the display
is powered with a 5 volt, 10 amp AC adapter.
Have read about unregulated
power supplies damaging sensitive low voltage components.

Is there any down side to powering the display
with batteries?


Allen in Dallas


Joined Mar 19, 2019
Allen a simple rectifier, capacitor filter and 5V regulator IC would be one simple solution. Downside of batteries is fading LED brightness as Vout drops and changing batteries. LEDs, in my limited experience, are fairly resistant to voltage variation and often use PWM voltage dimming on them.