Ryan Kremser wrote:

is there an easy way to add maybe 136 more address easily, previously i was
looking into using a led counter to accept a pulse to incriment the value
but now that i'm looking it seems to be a bit more expensive than i was
hoping. I need to be able to drive 6 - 3 digit (7 segment) displays. plus
an extra 10 could make another aspect a bit easier. Would it actully be a
good idea to use these outputs to control the led's or even with the
difference in price would the counters be a better solution?


If you're thinking of using 136 or more addresses to directly drive individual LEDs,
then I suggest that you look at an alternative method. Directly driving that many
LEDs, without multiplexing, would require a substantial power supply. 140 leds x 20mA
per led = 2.8amps, not to mention the complex wiring (thinking of a rats nest) to each led.

All that being said, what is the application? Why do you need 6 x 3 digit 7 segment displays?
What do they need to display, how frequent are the updates, what is the trigger
to update the display information, are the displays to be mounted adjacent to
one another to make a larger display, etc?

If we knew more about the application, perhaps we could suggest a solution that may be
easier and more appropriate to implement, rather than guessing.

That being said, here's my guess.

One solution I have in mind would be to use Maxim's MAX6958. The display is a 4 digit,
9 segment multiplexed display driver, with I2C serial data input. This solution still
requires a MAX6958 for each 3 digit display group, and a separate ucontroller/PC which
would receive the trigger(s), and to send the data/updates to the displays.

Some advantages a
1. The displays are multiplexed, therefore the overall current used is less than for a
static display.
2. The driving circuits are within an external chip, which removes the requirement
of constant refreshing by a microcontroller.
3. The MAX6958 has an I2C serial input (2 wires, data and clock), which makes it easier to drive.
The addressing of each device could be solved by using an external decoder, such as a
74HC4051, or CMOS 4051, which could gate the clock of the I2C.
4. The MAX6958 has only 16 pins, therefore there's less wiring.
5. You can get some free samples from Maxim, (limited to 3 I think) so you could play
with them before committing yourself.

If you want the datasheet, type in "MAX6958" into Maxim's search engine at their
website www.maxim-ic.com.

Then again, if you're feeling adventurous, you could roll-your-own by designing a
circuit that uses a PIC or similar microcontroller to receive the trigger data from
each source, and to drive each bank of 3 x 7 segment displays.

--

David