Calculating LED wattage.

M

Mak'er Grow

Well-Known Member
Which measurement is best for calculating the wattage ?
On the AC or DC side of the fixture.
Just did some quick measurements and they dont match up.
eg:
AC=117.8 @ 700mA
=168.5 watts
DC=100.5 @ 465mA
=216.1 watts
Mostly just wondering on what others have to think on this.
 
M

Mak'er Grow

Well-Known Member
greg nr said:
Just curious, but how does 100.5 * .465 = 216?

Or 117.8 * .7 = 168.8?
Click to expand...
Was looking at some older notes...gonna have to go back and redo the tests...arrrg...not a good start to my day...lol
Seems I hit "/" and not the "*"...my bad.
Either way they dont match up...even close.
AC=82 and DC=46 ...with some remainder.
 
greg nr

greg nr

Well-Known Member
I've had days like that. ;)

The way to rough it out is to add up the forward voltage of each led, and multiply that by the current of the driver (assuming a constant current driver).

So if you have 10 led's each drawing 3 volts at 1 amp, it would come out to 30 watts. Use a killawatt meter at the wall for easy monitoring.
 
M

Mak'er Grow

Well-Known Member
greg nr said:
I've had days like that. ;)

The way to rough it out is to add up the forward voltage of each led, and multiply that by the current of the driver (assuming a constant current driver).

So if you have 10 led's each drawing 3 volts at 1 amp, it would come out to 30 watts. Use a killawatt meter at the wall for easy monitoring.
Click to expand...
I'm not into buying a killawatt meter just to check a couple lights when I have other meters and a calculator that does same thing...lol
Also I'm not sure the killawatt will even do the DC side.
It was more of I got wondering about if DC side would give a more accurate measurement.
 
greg nr

greg nr

Well-Known Member
ac side will be a more accurate "measurement" of power used since it takes driver inefficiencies into account. DC side will be more accurate for light output. Both will require measuring amperage drawn and volts used.
 
1

1212ham

Well-Known Member
Search ac power factor, ac voltage and current are often a little out of phase. IIRC, voltage and current 180° out phase = zero power!
 
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