complex voltage drop question

[gashmore]

Think it is time to prototype. Ordered a few samples of 12v-24v lamps. One dedicated to a surgical examination and the others measured under various power conditions.
Thanks to all. Will report back my findings.

 

[gashmore]

Bought a set of 4 12v to 24v LED fixtures to test. Circuitry is encased in potting compound in the bottom of the housing.
On the test bench, powered by a variable voltage DC bench power supply and a LUX meter the LED output was a steady 200 LUX at 6" on axis throughout a voltage range of 12.2 to 24V. Output dropped to 190 lux at 12V and substantially less at 11V. Current remained between 3.01 and 3.11 Watts throughout the range. Under AC power the output remained the same 200Lux and 3 to 3.14 watts throughout the range. Oscilloscope showed 60Hz at the LED chip so apparently no rectification in the circuit.
One sacrificial unit was tested for over voltage. Noticeable increase in brightness above 24 volts and I let the smoke out after 30 seconds at 28V.

Looks like I can expect reasonably constant output to the end of 400' of 12/2 fed at 24v AC or DC.
Again, Thanks to all.