I've been advised in another forum ( ) to try and get hold of a 16F84 series PIC. I am completely new to PICs and programmers, so I would need a kit that would start me off. I'm looking to program a PIC to control RGB LEDs. I have been told a need to use Pulse Width Modulation so that I can fade each colour of the LED to produce any colour I want. Basically, I would like to use visual basic code to control the serial port to output a command somthing along the lines of "RGB[rrr],[ggg],[bbb]" (where [rrr], [ggg] and [bbb] are three digit values [from 0 - 255] for the colours red, green and blue) and the PIC decode it and powers the LEDs. I wanted to use a PIC so that I could detach the circuit from the computer and the LEDs would stay the same colour. Could anyone recommend me the things that I would need to produce a PIC/circuit capable of this. (I know there are things similar to this on the forum and Google, but they just fade through colours, I would like to be able to set the colour using a serial command) Thanks, Martin.
The easy way I think would be to grab a Olimex PIC-P18 board. It's got the crystal, voltage regulator and MAX232 for serial communications all set up. You only have to wire Tx, Rx to the right pins. For a programmer, they have several at the above site, I'd probably go with the PIC-PG2C or the PIC-PG1 if you use the development board and want to do it in-circuit. You can find tons of plans to make your own programmer, but these are pretty cheap and you dont' have to worry if you're having problems if it's the circuit or the programmer. If you are more comfortable using C than assembler, then make sure you get a PIC that is supported in the free version of HiTech C.
Here's a link to a couple of PIC12F629/PIC12F675 and PIC16F628 RGB LED controllers that I whipped up a while ago using JAL (http://jal.sourceforge.net/ http://groups.yahoo.com/group/jallist/): http://www.wahoo-wa.net/PICprojects/ -special [k]
http://www.dvarchive.org/RGBLED/ is pretty cool if you're good with super small surfacem mount stuff. (and I mean small like QSOP, makes a modchip install look like a walk in the park IMHO.)
Hello, I've designed a board which will control up to 40 LEDs through the parallel port. The board is designed around the MAX6956 chip from Maxim. PM me if you would like more details. Regards, Buddabing
I've came up with this using opto-isolators to protect the PC: (notes about this image: resistors need to be before the opto-isolator and the PC, i forgot to put a power source on the right-hand side) I just need to make Visual Basic output to the paralell port at 50hz. I've made a program already to create a steady(ish) 50hz(ish) output, I just need to get the opto-isolators to test it!!
A cheaper and simpler way is a ULN2803A, 8 darlington switches, 500mA per channel and base resistors built-in...
That optoisolator thing won't work. Optoisolators don't produce current. They are actually an LED and a photodiode/phototransistor in a box. It works like a relay but uses less power.
Actually optoisolators do produce current, just not much. The keyword here is Darlington. Using one transistor to switch another for lot's of current. cpemma, nice. Haven't seen these before. Have to pick some up.
Can anyone recommend a source for some decent RGB LEDs in the UK? I have seen some really awful ones, and I'd rather get some that have been previously tested by others. The ones specialk used look quite good!
I purchased mine on eBay from cwithk (http://stores.ebay.com/Chi-Wing-LED-product-shop); however, I would not recommend them because they are very low quality RGB LEDs. The LED dies are significantly off-center, so when this fact is coupled with the fact that they use water-clear lenses, the beam of each color faces a different direction. The reason they look good in the pictures is because all of the pictures are taken from the side (notice none of them are head-on). I would suggest using seperate LEDs that you can individually manipulate or diffused RGB LEDs, depending on your project. -special [k]
Rapid sell 3 Kingbright 5mm RGBs, different brightnesses, that should be quality. I think the brighter ones are 4-wire (common-cathode) types which may cramp your style. One's on offer ATM (see home page), but it's the lowest mcd.
I have 4-lead common cathode RGB LEDs and I haven't had a problem with them. The 6-lead RGB LED, which I assume are similar to the full spectrum LEDs here, are actually common cathode too, but because they use two blue dies (because blue LEDs are less efficient than green or red at producing the same amount of lumens), they have an anode for red, and anode for green, two anodes for blue (one for each die), and two cathodes. -special [k]
By "cramp his style" I meant you can't use a switching transistor like the ULN2803 darlington array I'd suggested earlier. The RGB has to be on the ground side of the switch, and on that NPN chip all the emitters are already commoned. Discrete transistors rule.
Any of the waterclear LEDs with more than one die inside aren't going to mix very well unless you have an extra diffuser. I've tried the Kingbright ones from Rapid, lots of Chinese RGB LEDs, and the only ones that are worthwhile are the Nichia 4 lead RGB leds in a milky package. All the others shoot light off in various directions or contain cheap crap gallium nitride dies that stop working rapidly when PWM'd...
Starbuck, is he really going to have experiance soldering QSOP chips if he hasnt used pics much? Hate to be mean but it is kinda obvious. Anyways, dunno about the LEDs but try a picaxe (techsupplies.co.uk) I know I keep recomending them to everyone, but they are in-circuit programmable, and are £1.50 each for one of the best types, they will handle PWM no probs, You can buy a kit which will give you everything you need for about £8 including programming cables, maybe the picaxe 18 pin project board? Forgot to mention, they are PICs programemd with a bootstrap to allow easy in circuit programming in basic, I think one is the 16F84 with a bootstrap
