I have built a LED cube that is 3x3x3 for a total of 27 leds. I have the 3 rows with anodes "+" together and the 9 columns are cathodes "-" together. As a result I have 3 wires to supply positive to and nine wires that will require sinking or grounding. I currently have the resistors on the nine columns as I thought that would be the best place to put them.
Now for the question, I know I need something like FETs to sink the columns and I might need FETs to supply power to the positives, can anyone make some recommendations?
Also, if you are aware of a source that has quick shipping to the USA let me know.
TPIC6B595 for sinking.
Resistors for sourcing, with TPIC6B595 to take current away from the off layers.
Available at digikey for shipment.
Watch for 5 mS to go by (millis), do other stuff
When 5mS gone by:
Shift out 0 to turn all cathodes off
Shift out 0s for anodes to be on, 1s for anodes to be off (reverse logic - a 1 will turn on output & pull anode low)
Shift out 1 to turn next cathode on.
increment counter to keep track of which layer is being driven on next (0,1,2), reset to if reach 3
Try daisy chain with just 2 - shift out B11111111, B10000000 to turn all off
then Bxxxxxxxx, Bx1000000 to turn 1st cathode on,
then Bxxxxxxxx, Bx0100000 to turn 2nd cathode on,
then Bxxxxxxxx, Bx0010000 to turn 3rd cathode on,
Thank you for the quick response CrossRoads! Your schematic makes it look fairly easy. I can finish my cube using the chips you show. One bad thing is, my LEDs are set opposite of the ones shown in the schematic. I have 3 positives and 9 negatives. Basically, I connected the positives of the row together.
Is your schematic still the best choice? I should have done a little more homework before I soldered my cube up.
Mostly. Use the shift registers to pull the cathodes low.
Use UDN2981 to source the current into the anodes; can be controlelled by shift register, or by arduino output. Or PNP transistors./P-Channel MOSFETs. Low = On, 5V = off for the transistors.
Hard to find the UDN2981 for some reason - none at digikey, mouser, avnet.
These transistors should work okay.
You're only sourcing 180mA, so really overkill, but the next price step down seems to be 5 ohm Rds, 700mW rated parts. With 180mA being sourced, thats 900mW.
I am very grateful for your help! I will be ordering those parts today hopefully.