hello, world. long time listener, first time caller. i'm hoping this is the right section.
a couple caveats:
i am not an engineer, nor do i play one on tv. thus, i am fairly ignorant re. the exact physics behind what i am doing.
i am not a programmer, either, but i've had some luck with arduino. hurray, arduino!
ok, so here's my issue. i am looking to fade some high powered (2.5-3.5v, .5w) leds with a tlc5940. i have the tlc5940 libraries, and have run the code i intend to run (a variation on the example sketch "fades") successfully on my breadboard. the breadboard is powered by a 9v wall wart running into a 7805 circuit with smoothing caps etc, and although i do not own an oscilliscope, i am told that the setup makes for a relatively smooth, noise-free ~5v power supply. i have not had problems with it in the past.
here's my schematic:
the problem arose after i finished soldering. i've built the board exactly as i had it on the breadboard, including the power supply, a basic 555 flip-flop switch controlling power to the arduino, and the tlc5940 rigged as per the "Hardware Setup" pics here.
when i hook the arduino up to the headers on the board i've built and hit the switch, i get 4.96v to the arduino. the rest of the board is on the same power circuit, but is not controlled by the switch.. and is also receiving 4.96v. the lights, however, fail to do their light thing... until i get my fingers close to the gsclk (pin 3) wire coming from the arduino. when i do this, the 5940 responds by cycling its first pin over and over. the rest of the -LED pins on the 5940 are doing nothing according to my multimeter.
my thoughts on the possible problems are..
1)i've made some glaring error in my schematic
2)when the circuit is powered on, the 5940 is receiving power before the arduino is turned on (via the pushbutton).. thus when it starts up it has no control signal. i'm not sure if this is a problem, but cycling the power doesn't seem to help, nor does resetting the arduino.
3)there is some sort of interference going on with the pinouts from the arduino to the 5940, specifically pin 3. why does it begin to turn on when i get close to it? and why isn't it running the arduino sketch when i get close to it instead of just cycling the first pin on the 5940?
4)pin 3 on the arduino is haunted, and needs my life force in order to do its job, albeit poorly.
i'm certain the 5940 is not dead, i have traded them off the working circuit on the board. i am also fairly certain i have no shorts on the finished board.
i'd really appreciate it if anyone could help out. arrgh.
~Sprinkels
edit: it's 5940, not 5490 =p
