What I really need is a solar powered lighting fixture with a motion sensor to light up my back yard shed.
On Mon, Jan 11, 2016 at 10:45 AM, Jim Cathey via Mercedes < mercedes@okiebenz.com> wrote: > You can buy LEDs with the resistor already integrated. >> > > Better to supply your own. > > LED's, like _most_ semiconductors, may not be wired directly > in parallel. Most semiconductors have a positive temperature > coefficient, which means they draw _more_ current as they heat > up. Resulting in more heat, thus yet more current, and thermal > runaway, and device failure. (Incandescent lamps have a negative > temperature coefficient, which means they balance naturally when > used in parallel.) > > So, for LED supplies you either need a bunch of LED's in series, > with _one_ current limiter, or you parallel the LED _and_ its > individual current limiter, times N, or some kind of series-parallel > arrangement representing both approaches. > > For a 12V supply I'd stack perhaps 3 3.6V LED's in series, and > use one resistor, making one 12V lamp bank. Times as many banks > in parallel as you needed to get sufficient light. > > Remember that a simple resistor as a current limiter represents > totally wasted power. Less resistors/resistance == longer > battery life. > > More complex circuits resembling switching power supplies are > not uncommon. What you are after is a constant _current_ supply, > not a constant _voltage_ supply. > > Certainly when I strung them up in series they wouldn't do anything... >> > > Either you didn't wire them in the same direction, cathode to anode, > or you didn't have enough voltage to push any current through their > stacked junction voltages. Either will keep the photons inside... > > -- Jim > > > > _______________________________________ > http://www.okiebenz.com > > To search list archives http://www.okiebenz.com/archive/ > > To Unsubscribe or change delivery options go to: > http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com > > _______________________________________ http://www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
