Arduino + MAX7219 + Eight 7-Segment LED.

Forum 2005-2010 (read only) Hardware Interfacing
1

I want to display 8 digit number using Arduino, MAX7219 and eight 7 segment LEDs.
I read everything I could find about it, but I'm not sure on what resistor I should use for Rset.

The 7segment LEDs have 3.8v forward voltage and forward current of 5-10mA.
After looking here( Arduino Playground - MAX72XXHardware ) I'm guessing that I need a 49kΩ resistor.
Is that right?

Also, would it work if I wire everything up without capacitors?

2

Hi,

I want to display 8 digit number using Arduino, MAX7219 and eight 7 segment LEDs.
I read everything I could find about it, but I'm not sure on what resistor I should use for Rset.

The 7segment LEDs have 3.8v forward voltage and forward current of 5-10mA.
After looking here( http://www.arduino.cc/playground/Main/MAX72XXHardware#SelectRSet ) I'm guessing that I need a 49kΩ resistor.
Is that right?

I would go for a 56k resistor. Do you have the part number or a link to a datasheet for the 7segment, that would help.

Also, would it work if I wire everything up without capacitors?
http://www.arduino.cc/playground/uploads/Main/MAX72XX_Schematic.jpg

It will probably work, but is not recommended!. Omitting them can lead to errors that are really hard to track down. (Showing up every other thursday, when the weather is a bit humid)
But it won't break anything leaving them out for testing purposes. Keeping the wiring very short helps a bit.
Eberhard

3

Hi,

I want to display 8 digit number using Arduino, MAX7219 and eight 7 segment LEDs.
I read everything I could find about it, but I'm not sure on what resistor I should use for Rset.

The 7segment LEDs have 3.8v forward voltage and forward current of 5-10mA.
After looking here( http://www.arduino.cc/playground/Main/MAX72XXHardware#SelectRSet ) I'm guessing that I need a 49kΩ resistor.
Is that right?

I would go for a 56k resistor. Do you have the part number or a link to a datasheet for the 7segment, that would help.

Also, would it work if I wire everything up without capacitors?
http://www.arduino.cc/playground/uploads/Main/MAX72XX_Schematic.jpg

It will probably work, but is not recommended!. Omitting them can lead to errors that are really hard to track down. (Showing up every other thursday, when the weather is a bit humid)
But it won't break anything leaving them out for testing purposes. Keeping the wiring very short helps a bit.
Eberhard

part# SM4210

I could not find the datasheet though

Thanks for you help