Large 7-segments with WeMos D1 Mini
Posted: Fri May 15, 2020 3:14 pmHi all,
I'm working on controlling 12 large common-cathode 7-segment displays (it's actually 6 displays with red and green) from a WeMos D1 Mini. The person I bought them from said they could be powered with 5v or 12v with 100-330ohm resistors. I tried 5v with 200ohm, 100ohm, 44ohm, and 20ohm resistors (just probing each pin, but only 200ohm on the dot for fear of frying it), but nothing lit up except the dot with 200ohm. (I assume that's because the dot has less actual LED's in it?) But 12v with 100ohm resistor lit up everything, no problem.
From my own probing and testing, each segment seems to pull around 8-9mA (max 10mA, I think.) Seems like 5v is only able to light up the dot, so powering it from the D1 Mini is out.
Other than what's printed on them (which, to me isn't super helpful), and what the person said, I have no idea on the specs of these displays. Is there a way to find out (without frying anything) what kind of resistors and voltage will work?
Also, I'm planning on using TPIC6B595N shift registers because I heard that they can sink/ground bigger currents (data sheet for them says up to 50v I think?). I have a simple schematic that I'm working on, but I really have no idea how to daisy chain them to control more than just one digit. Can someone help me out?
I'm working on controlling 12 large common-cathode 7-segment displays (it's actually 6 displays with red and green) from a WeMos D1 Mini. The person I bought them from said they could be powered with 5v or 12v with 100-330ohm resistors. I tried 5v with 200ohm, 100ohm, 44ohm, and 20ohm resistors (just probing each pin, but only 200ohm on the dot for fear of frying it), but nothing lit up except the dot with 200ohm. (I assume that's because the dot has less actual LED's in it?) But 12v with 100ohm resistor lit up everything, no problem.
From my own probing and testing, each segment seems to pull around 8-9mA (max 10mA, I think.) Seems like 5v is only able to light up the dot, so powering it from the D1 Mini is out.
Other than what's printed on them (which, to me isn't super helpful), and what the person said, I have no idea on the specs of these displays. Is there a way to find out (without frying anything) what kind of resistors and voltage will work?
Also, I'm planning on using TPIC6B595N shift registers because I heard that they can sink/ground bigger currents (data sheet for them says up to 50v I think?). I have a simple schematic that I'm working on, but I really have no idea how to daisy chain them to control more than just one digit. Can someone help me out?