I have looked at similar thread but as I dont have a lot of electrical know-how I wondered if someone could help me wrp my head around this.
I have a 44 sets of leds (3 in a set) that I want to run independantly from one arduino.
I have had some success using the HT16K33 chip, but this meant I had to cut one led out of each set so they would run on the 5v available.
This led me to the ULN2803 and I thought if I connected the HT chip to this, I could then run my led sets off of a 12v power supply solving my problem.
Here's an idea of the schematic, but so far it doesn't work as hoped.. all leds from each ULN chip come on at the same time so I can't control the sets individually like I could before I added in the ULN chip.
All my leds are setup in a common annode config which leads me to think the HT chip may not be happy with this as it's aimed at common cathode displays?
Thanks for any ponters!
-Edit-
What the schematic doesn’t show is that there are 6 ULN chips in total, two for COMM1, two for COMM2 and two for COMM3 to make up the 16 inputs for the HT chips 16 row outputs.
With only 44 groups of LEDs and not using the keyboard functionality, the HT16K33 https://cdn-shop.adafruit.com/datasheets/ht16K33v110.pdf can be regarded as supporting common cathode or common anode led configurations. You may have to swap rows and columns, though.
Look at the data sheet for the HT1632C https://cdn-shop.adafruit.com/datasheets/ht1632cv120.pdf for examples of circuits which augment the outputs of a LED driver, with transistors or transistor arrays, in order to drive higher voltage LED configurations.
Depending on how your leds are configured, you may be better off using these two chips:
mic5891 high side shift register
tpic6b595 low side shif register
instead of the HT16K33.
This would only use 4 arduino pins in total. The coding is, however, a little more complex because you have to handle the multiplexing and, if necessary, display brightness control yourself.
Since the HT16K33 appears to have a built in constant current driver, I'm not sure that it is suitable for indirectly driving a load as you are proposing.
