Ok, not really sure if this is in the right section, if not, please feel free to move it to the correct section mods. Right, my sister is in her 4th and final year of uni doing a BSc in Product Design. Her final year project is making 3 outdoor LED Light prototypes. Each Light will have 84 LED's, for a total of 252 LED's. She has designed, made the casing, soldered the LED's into her acrylic frames. She, like me, has never done electronics yet she keeps asking me for help, that is where you guys hopefully come in. The lights will be connected to an arduino mega 2560 board. She needs a power supply to power the arduino, the drivers and the 252 LED's. She is using 5mm LED's and they are rated at 3V - 3.2V. She bought 500 LED's on ebay and it doesn't tell us the current rating, so we don't know which power supply will be able to power that many LED's. She has a circuit diagram already, but that is getting checked by her lecturer tomorrow. I can post it if it helps. Also, any ideas on which resistors etc she'll need? Also, at some point she will need to code the arduino which I may be able to help with using my A-Level in computer science, though that was some 7 years ago. Any help or suggestions are welcome Pic of Lights *UPDATE* LED's use 20mA Using 4 drivers instead of NPN transistors
Found the LED Specification, the LED's are 20mA each. Here is the current circuit diagram which may change tomorrow (she now has 4 drivers instead of NPN transistors) Grid Layout and here is a multiplexing diagram
Hi guys This is the infamous lil sister, just a minor detail I forgot to mention ....only one LED in each pendant will be lit at one time (so 3 LEDs in total) like an LED Cube. I just got back from Maplins and I purchased a Regulated 12V 500mA AC Adapter so hopefully it should power it fine if not I can always return it. I also added an image (above) of the LEDs in the acrylic frame so you have a better idea on the LED layout. Any idea on how I will code this bad boy? I should hopefully be sorting out the circuit board by tomorrow...if not you'll be hearing from me again
I can't see the images at the moment, as photo sharing websites are blocked at work. If you're only going to light one LED at a time, you *might* be able to get away with powering them directly from the Arduino. I can't imagine that the Mega will differ too much from the Uno or Duemilanove in this regard, but the current limit is 40mA per pin with an overall draw of 200mA. However it's far safer to use an external power supply and attach a transistor or driver to the Arduino pins. In terms of coding the Arduino, the best place to start is the online help pages or the examples built into the IDE. Grab a few spare LEDs & resistors and just get cracking . You can study books to learn the theory & syntax all you want, but the best place to start is just to dive right in. What I can't figure out at the moment is what you need the Arduino for? Do the lighting conditions need to change based on a sensor input, or do you want to have some sort of "chasing lights"/persistence of vision arrangement? EDIT: It's worth noting that those current limits are the absolute maximum for the atmega328 - in real life you probably don't want to get anywhere near those values.
Without any knowledge of how the LED's are interconnected, we are lost. Those two 16 way cables will look mighty ugly... ideally you need a transmitter/arduino + three receivers/PSU's. Sorry ! dunx
they are about 15 Meters long and they are all working but in the middle about 1/2 a meter isnt working i have tried tapping it and there is a little blue spark from one of the LED's, what can i do to fix this? Help
