integrated-circuitvoltage-regulator
My first post here, please keep in mind that I hardly know anything about electrical engineering so please keep any replies in layman terms, thank you!
I bought this 30cm white LED strip.
It's set up to run from 12 volts. The thing is I would like to use it at 6 volts. I can see that there are soldered IC chips on it: an M7 chip and a 78L05 chip; from what I could find out the 78L05 chip is a voltage regulator.
What would be the simplest way to get this to run from 6V?
This is very nearly the description of the first half of a common PC power supply. You could learn how they work, and then use many of the parts from one. But they are not simple.
What that part of the circuit does is rectify the input to a high voltage DC. The resulting DC is then run through a switching supply with isolating transformer to get the desired voltages. Regulation is done by looking at the output voltage and using it to control the switching system upstream.
It is rather involved, but this may be necessary in order to get the wide input range you seek.
Do you know that the horizontal strips of a breadboard are all connected together (except sometimes in the middle)? To me this looks like you have shorted the input to the output of the 7805. (Or maybe the output to te ground, my view is blocked by the capacitor.)
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OK, next step. You are using a plain old 7400, no LS or HC or any other letters between the 74 and 00? That old chip requires 5V. If you used it at 9V you can't assume it is still working correct. It might, but don't count on it.
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I can't make sense of your LED question. You don't mention a series resistor, did you use one?A LED nearly always requires a series resistor. For starters, take 1k.
Best Answer
To save the hassle of trying to modify a device to take a different voltage, I would personally consider using a "step-up" or a boost DC-to-DC converter to simply provide the required voltage.
One like this boost converter from eBay would be able to take in 6 volts and supply 12 volts on its output.
Your eBay listing did not provide amperage/power requirements, but the ~10 watts this provides should be enough