I have to take a break from the circuits and layouts and go back and verify a couple of calculations. I am referring to the Rset for the MAX7221. I need to be sure that this is going to be correct in relation to the 7-Segment units chosen – and also the discrete LEDs for the indicators.
- 7-Segment: NKR161B
- Vf = 1.7V per segment
- Maximum forward current = 30mA
- LED:
- Vf = 2.0
- 20mA Test current
For Rset,
In theory, the MAX7221 should be able to drive the 7-Segment displays directly using a 50KΩ resistor. It also looks like the discrete LEDs for the indicators can be accommodated. What the impact will be in real terms of brightness and evenness of illumination, I will wait to see it for my self.
Rebooting Electronics 