I was looking to reverse engineer those 7 segment mini LED displays to make a bigger one with 6 digits on them in order to display the time and other values.
I was successful in getting everything to work with a real time clock 1307 except that the leds are more dim than i need them to be.
I set Rset to be 10kohms at the beginning of the max7219 chip and each segment contained 4 LEDs connected with a common anode topology with each LED containing 200ohms as a current limiting resistor as shown in the attachments below. (Edit:The 1k resistors were later swapped out for 200 ohms)
I set the brightness to the max possible lc.setIntensity(0,15); I also tried used different LEDs, Rset, and current limiting resistor values to no avail.
I would get the brightness i want when plugging in the 5 volt line straight into the common anode node of one digit as compared to running it via the max7219 led driver chip which leads me to thinking that the max7219 is limiting the current being delivered to the leds…
Here is the datasheet of the LEDs i specified for the display https://datasheet.lcsc.com/szlcsc/1806080424_HONGLITRONIC-Hongli-Zhihui-HONGLITRONIC-HL-PC-3216H233W-9000-16000K_C219232.pdf
Any insight on this topic would be greatly appreciated