I'm planning a 4 digit 7 segment display. I've already built a few, but I have a new problem. Until now, I've been using individual digit modules that have a forward voltage less than 5V. So I drove common cathodes with 2N7002's and the segment anodes with a 74HC595 and current limiting resistors. It works very well.
Now I have some larger digit modules on order. Each segment uses multiple LEDs to illuminate the larger area. These are usually connected in series... this makes the operating voltage as high as 6 or 9V (depends on the LED type/colour).
The question is, what is a good way to drive them?
My thinking was to use common anode diplays, with FETs and current limiting resistors driving the segments, and four high side drivers for the anodes. The segment drive is easy, since it's open drain. Is there an easy solution for the anode drive? I can see how it would be done with transistors, but as I see it, I would need two transistors and some resistors for each anode. I expect to have +9V or +12V available to drive the display. Is there a chip I can use? I have been looking around online, but all the solutions I see are for 5V systems.
TPIC6C595 or TPIC6B595.
6C can sink 100mA per output, 6C 150mA, from 50V source.
1 chip per display, or 1 chip and 4 highside transistor pairs if multiplexing.
(I say pair because the PNP or P-channel MOSFET will need its base/gate pulled to 12V to turn it off, and a simple NPN is used between the Arduino the transistor to pull the base/gate low to turn the PNP or P-channel on).
Nice. I could cascade two of the IC's and use the second one to drive the high side transistors. Because it's open collector, it could drive a single high side transistor per digit.
Yes. Open Drain tho (MOSFET), not Open Collector (BJT).
LED Display Drivers are available at Mouser Electronics. It used to maxim Integrated, LED Display Drivers 8-Digit LED Display Driver.Digit LED Display Module is one of the most popular and widely available display module.
recyclenation:
LED Display Drivers are available at Mouser Electronics. It used to maxim Integrated, LED Display Drivers 8-Digit LED Display Driver.Digit LED Display Module is one of the most popular and widely available display module.
Of course, there are many drivers IC's on the market. Do any of them directly support LEDs that operate over 5V, as I asked about?
TPIC6B595 and TPIC6C595 as I mentioned earlier.
I use up to 12 on this board to combine Arduino functionality to drive LED strips as segments of 7-segment displays.
http://www.crossroadsfencing.com/BobuinoRev17/
Thanks. To clarify - I already have a few TPIC6B595 on order. They will drive the segments perfectly. I'm resigned to using it to drive transistors as the high side digit drivers. My hope was to find an IC that would handle the high side. Ideally, it would be multiple PNP or P-channel mosfets with inputs that the open drain outputs of the TPIC6B595 could "pull down". The circuit is common. It would just be nice to have it in a package, instead of using discretes. For so few digits, I may end up biting the bullet and using discrete PNP's.
But I was mainly addressing what seemed to be a shill for Mouser. 
