Hello all, this is my first post to this forum and I spent several hours researching so I'm hoping I haven't missed a thread on the same topic somewhere (apologies in advance if so). I'm in need of a scalable solution for multiplexing/demuxing using an Arduino Uno that doesn't utilize I2C (long story, but the I2C bus on my Uno is otherwise occupied and I can't have LED drivers taking up I2C addresses on my network). Because of my application, I need to stick with the Uno CPU so I can't take advantage of boards like the Mega which would provide native ports.
I've found a number of threads on port expansion, reading sensors, driving outputs, etc. All very helpful. I think I've settled on a solution for multiplexing the input of multiple sensors (using 4051's-- this seems to be the easier part). I'm having trouble settling on the right solution for my outputs.
Here's the scenario. I need to be able to expand the number of output ports on my Uno so I can control up to 16 LEDs or other devices (~ 200ma mini relays). No high-current LEDs needed here (total anticipated current draw on any one output would be 200ma or less), but I want the flexibility of using the outputs to drive individual LEDs (or strings of up to 10x 20ma LEDs on a single output) or to drive relays (small relays, not mains-type relays). I'd also like to have PWM available for the LEDs (though that's not a hard requirement).
I found with the analog multiplexers (4051) that the outputs assigned were only momentary (also found that in this forum, sadly after hours of hitting my head against the wall)-- I need a solution where the Arduino can "set it and forget it" for each of 16 ports. I found the I2C LED drivers which look great, except that they take up I2C addresses (which I need to preserve for my application).
Sorry for the long story, but I want to set the stage. I'm thinking I would be all set if I could find a 16-port driver that would power my LEDs and also my relays. Because of the ~200ma current needs for both, I was also thinking of using a darlington array to drive the LEDs and relays from a separate 5v supply.
Thoughts? Any recommendations for 16 ports of latched output with optional PWM that could be used (through darlington arrays?) to drive ~200ma of LEDs or a small relay on each port?
Thank you in advance for any guidance you can provide!