I'm trying to make a little project that would be an LED voltage meter, but I have a few requirements that I'm not sure how to implement:
I need all components to be surface mount, through hole is a deal-breaker.
Powered by 2 CR2016/CR2032's in series.
Between 10-20 LEDs BUT in dot mode, so if the 5th LED is on, 1-4 would not be.
And small, the circuit needs to fit on a credit card sized PCB.
I'm aware of the LM3914 but the only surface mount I can find is about $3 and that blows the budget.
I know I could do this with a microcontroller but the project is more for learning, so I figure there's got to be a way to do this without one.
I'm thinking the voltage signal would be coming from an opamp (so I can adjust the gain and offset) then to whatever circuit to drive the corresponding LED. If I adjust the gain and offset so the range would be 4.0V to 5.0V each LED would correspond to a 0.1V step.
Also the LED's do not need to be bright (in fact it would be better if they were more on the dim side for power consumption).
Thanks, I hope I explained myself (I'm still very much a beginner to electronics).
I should say, I don't really need the circuit designed, I just don't know WHAT to look for to design it.