I think I've been on here discussing my project before. I have a MIDI keyboard here, now, I've written all the software that makes it so when I play the keyboard, I've got 12 LED's that turn on and off with brightness being dependant on how hard you hit the keyboard and the LED being which note you push (or, two LED's if you hit two notes). Thx Arduino Mega!!
I'm more of a software guy just kind of wandering into the hardware side of things now to help a friend with her art project. The problem now is this: These LED's are going in lanterns, the LED's we're going to buy can be found here: http://cgi.ebay.com/100-pcs-5mm-White-LED-Lamp-18000mcd-Free-Resistors_W0QQitemZ160356124113QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item2555f845d1&_trksid=p3286.c0.m14
My friend has a vision of 48 lanterns, 4 lanterns for each semitone (between C to B inclusive). With 4 of those LED's in each lantern that would be 192 LED's!! (that's a lot)
About the LED's:
The LED's say they are Forward Voltage: 3.0 - 3.2V DC Maximum Current: 20mA Continuous, 50mA peak for 10% Pulse Width
if I'm going to be using PWM to control the brightness, and if the player hits every key at once at full strength, this could power all LED's at a full duty cycle, requiring 50mA (because it's on peek)
so that would be 50mA, at 3.2DC... 3.2*0.05 = 0.16 Watt per LED
0.16 * 192 = 30.72 Watts of electricity required.
Would this mean I could get away with purchasing a 12VDC power supply at 4A current? (providing me with 48W to play with)
I don't know much about the resistors I'd need to do this, but I'm assuming a 470 ohm resistor connected to each LED in the circuit would be fine? Will putting resistors in the circuit change the 30.72W required power assumption I'd calculated??
Also, for each note on the midi keyboard, it's going to power 4 lanterns (with 4 LED's in each), so 16 LED's. @ 50 mA, this would be 800mA, so could I use a BC337 transistor to switch these groups on and off??
Once again, I'm not really an engineer and help on putting this together would be greatly appreciated!!
Thanks so much,