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Yea those "5w" ers are basically 2 "3W" chips in series.. so each one replaces 2...
Another thing about led's is watt efficiency increases w/ lower current. Sort of the less amps, less heating since more energy is released as photons.
Most if not all bb's are run low in amps ( about "2W" worth) anyways thus they can get away w/ flimsy heat sinks, even w/ the fans..
At 700mA you get 100% of rated output.
At 1400mA one expects 200% but gets say 185%
Of course gross amount is less..but 2 @ 700 exceeds output of one at 1400.
Lower currents are more linear though.
Err brightness scales w. voltage w/ LED's
Hmmm.. Seems contradictory (guy is an electrical engineer though).. but current draw increases more w/ voltage changes but efficiency decreases.. Must even out "in general"
Of course most "think" current not voltage.
But the voltage changes w/ LED are small for a large increase in current (and on/off or lifespan) w/ a fairly sharp on/off threshold that you noted
Got to think about this a bit.
Lots of interesting things w/ LED's..link below is just for "fun"
Another thing about led's is watt efficiency increases w/ lower current. Sort of the less amps, less heating since more energy is released as photons.
Most if not all bb's are run low in amps ( about "2W" worth) anyways thus they can get away w/ flimsy heat sinks, even w/ the fans..
At 700mA you get 100% of rated output.
At 1400mA one expects 200% but gets say 185%
Of course gross amount is less..but 2 @ 700 exceeds output of one at 1400.
Lower currents are more linear though.
Err brightness scales w. voltage w/ LED's
SIMPLISTIC BULB VERSUS LED CONCLUSION:
1) A light bulb lumens (brightness) falls off a factor of 3.5 times faster compared to that of a LED for the same voltage drop in track voltage.
2) When running from a loosely regulated track voltage and you want the light source to have relative constant brightness, use a LED.
LED Vs Bulbs - Mark Gurries
Education about Digital Command Control (DCC) used in model railroads to run trains. This site is also a distribution point of my DCC presentations in PDF format. My Model Railroad Website
sites.google.com
Hmmm.. Seems contradictory (guy is an electrical engineer though).. but current draw increases more w/ voltage changes but efficiency decreases.. Must even out "in general"
Of course most "think" current not voltage.
But the voltage changes w/ LED are small for a large increase in current (and on/off or lifespan) w/ a fairly sharp on/off threshold that you noted
Got to think about this a bit.
Lots of interesting things w/ LED's..link below is just for "fun"
Thermal management of high power HB LED
The efficiency of transformation of electricity into the light is a key point for HB LEDs. Efficiency of the typical LEDs achieves 40% to 50%. That means that more than 50% of the electrical power …
3n-technology.com