Hello, I own a small coffee shop. I recently bought out the store next door to expand my sitting area. As a result I will have a lot more wall space to decorate .
I have this old wooden frame that is divided into 3 squares wide x 6 long. My plan is to use white LEDs and diffuse it with different color tissue paper and put glass over the frame, and run a few sequences with the Leds. (I know it sounds hokey, but for some reason my customers love things that are bright and blinky. maybe it's all the caffeine?) Each individual square is 6"sq, so I plan on using 9 LEDs in a 3x3 array (total of 162 leds). Each set of 9 LEDs will be treated as one LED and hooked up to a 74HC595, and ULN2803 and programmed with a pictcontroller with a 9v DC wallwart. From my calculations peak V will be 3.24V, so I am not worried about that. I am unsure of what resistor value to use. Since the 74HC595 does multiplexing, only one square will be on at a time. If I calculate resistance values based on that - 2.8 forward voltage, 9v dc, 20ma, 9 leds into a LED calculator, it tells me to use three 33ohm resistors in a 3x3 array. Is that right? Or should I be using a resistor for each individual LED?
**broken link removed**
I have this old wooden frame that is divided into 3 squares wide x 6 long. My plan is to use white LEDs and diffuse it with different color tissue paper and put glass over the frame, and run a few sequences with the Leds. (I know it sounds hokey, but for some reason my customers love things that are bright and blinky. maybe it's all the caffeine?) Each individual square is 6"sq, so I plan on using 9 LEDs in a 3x3 array (total of 162 leds). Each set of 9 LEDs will be treated as one LED and hooked up to a 74HC595, and ULN2803 and programmed with a pictcontroller with a 9v DC wallwart. From my calculations peak V will be 3.24V, so I am not worried about that. I am unsure of what resistor value to use. Since the 74HC595 does multiplexing, only one square will be on at a time. If I calculate resistance values based on that - 2.8 forward voltage, 9v dc, 20ma, 9 leds into a LED calculator, it tells me to use three 33ohm resistors in a 3x3 array. Is that right? Or should I be using a resistor for each individual LED?
**broken link removed**