MAX7219 Binary Clock question

Hi,

I designed a binary clock project that uses a max7219 8 digit led driver. I use 3 of the digits to display the time in binary, and the other 5 to drive 7-segment displays for translation (for those that cannot read binary). It looks kind of like below picture

_B__B__B

_B_BB_BB

_B_BB_BB

BB_BB_BB

HH:MM:SS

(ignore the “_” uderscores, they are there for spacing only)

where "B"s are LEDs translating in BCD what is in the “H ours”, “M inutes”, or “S econds” 7-segment digit display at the bottom of the column. A toggle switch turns the 7-segment displays on and off. The high order Hour 7 segment display is either a 0 or 1 (using 12 hour clock) so I control it directly by the microcontroller.

The project works great with red LEDs, but when I try to use other colors the LEDs burn out. I have tried changing rset up to 50k and I still burn them out.

The datasheet for the colored LEDs I am using can be found at:

http://www.well-ton.com/datasheet/HH-10PGD-50.pdf

Surely I am overdriving the LEDs with current. There are no current limiting resistors because I didn’t think I needed them with the max7219. I don’t know how to measure the actual current of the circuit since the each LED is only on a portion of a second.

Can anyone please help me figure out what is wrong? I went through the trouble to burn boards and give a few of these away as gifts, then the LEDs (other than red) started burning out.

I know the voltage drop of the colored LEDs (other than Red) is around 3v, where the red is 1.8v. I have no trouble with the 7-segment displays, only the LEDs. Also, I never mix colors of the LEDs.

Thanks,

Trey