binary LED driver

Hi guys,

I'm looking for LED driver, wondering if you guys know if it actually exists. I wanted the functionalities of an LM3915 - a dot/bar display driver, but having a binary input like CMOS 4515 (4-Bit Transparent Latch/4-to-16 Line Decoder). I saw a STP16C596, which does the job but then I'll need to through in another MCU because of the serial input.

Is there anything like that packages already?

Thanks!

William

the lm391x are pretty much analog voltmeters, but you're asking for a digital device?

what's wrong with the 4515, that seems to be exactly what you want ... making it function as a bar graph driver is a software issue... you just feed it a string of numbers and the outputs turn on and off?

well, I really wanted a bar graph. So something like if I feed it 0100, I want all the lower bits to turn on as well. If I do this with OR gates, I'll need at least 1 for each output, which is a bit too much for a strip of 40 LEDs.

Why not use a PIC (or other micro-controller) to do it?. Depending how bright you want the LED's you may be able to drive them without any extra driver transistors - but with the usual current limiting resistors.

ok, I see what you mean ... the 4515 only turns one of its sixteen outputs on at any given time ... so you need to strobe it to give the appearance that more than one output is working at the same time... again a software problem.

if you have four lines available, check out the 74hc595 serial load shift register... daisy chain registers to get however many outputs you need, all run off the same three wire serial connection. now, use a lookup table to translate your decimal numbers into a binary scale, and bit bang that binary number out to the register.

dec = bin, 0 = 0, 1 = 1, 2 = 3, 3 = 7, 4 = 15, 5 = 31, etc etc... so you end up with a pattern like a bargraph:

0 = 00000000
1 = 00000001
3 = 00000011
7 = 00000111
15 = 00001111
etc

Why not use EPROMs? You can probably find some old 2716 etc To save space piggyback in order to get the 40 outputs.