multiple seven segment displays

I am hoping to use several 7 segment displays with the Arduino and had a few questions. Obviously with each digit needing 7 pins to control you would run out of pins rather quickly on any board. What is the best way to add more segments than pins? I have read that you can connect all of the control pins together and then connect each anode to a separate pin and this way you can control which digit you are controlling. The problem I see with this is that you are creating a PWM effect that divides the brightens between the various LED's. ie if you had two digits they would be half as bright.

Check into the following chip. It was made for this purpose.

http://www.st.com/stonline/products/literature/ds/10411.pdf

You would definitely want to use one of the specialized chips designed for multiple digits if possible. It's cheaper to use some more basic chips and complicate things but not really worth any cost savings.

I put together a 4 digit using a 4511 BCD to 7-seg converter then control using a PCF8574 i2c port expander. 4 bits for BCD control and 4 bits connected to a NPN transistor for each cathode. This setup is mainly because it's cheap parts I already had around.

What I found is that it takes about 5ms for each digit to be bright enough while not having a scan flicker. With more complex programs, it will start to be a problem because some routines can easily be over 5ms.

Use an AS1107 chip. You can control up to 8 x 7-segment displays using just 3 pins on the Arduino.