I'm doing some VERY amateur prop building for an upcoming night of cosplay and I'm trying to create a throbbing/pulsing crystal for the top of a magic staff. Initially, I was just going to use a simple red LED circuit driven by a 9 volt battery, no muss no fuss. But I discovered that I can power the blue channel on a small strip of 5050 LEDs (3 diodes, normally 12v) with 9 volts beautifully, rather than drop $$ on individual blue LEDs.
Solid on is no issue, but fading on and off would be brilliant. Trouble is most of the fading circuits I've found are strictly for one or two low power LEDs. They all call for a 555 timer, 1k-ish resistor, 100uf-ish capacitor and a general purpose transistor. For my LED strip, the transistor was underpowered, but a N-MOSFET gets the job done. Here's the Schematic:
Breadboarding this will light the LED strip, but I don't get any fading. I do see a very quick, but barely noticeable blink ever 2 seconds or so, which I suppose is better than solidly on, but not the effect I was hoping for. I've tried swapping out differently rated capacitors and resistors, but aside from slightly different timing, I haven't had much luck. My understanding of timers and capacitors is only a few days old, so it wouldn't surprise me to know I completely missed my mark. Also note that I've no intention of using a 'duino' of any kind because I want minimize the components I need to hide on the staff itself.