OT, any electricians or electrical engineers on here? i have something that

[Bill R.]

i'm wondering about... with a 120v transformer thats rated at 100 watts 12v and i have 5 20 watt 12v mr16 bulbs being run by it... If i substitute 1 watt led's with mr16 bases with the power consumption drop or does the transformer consume 100 watts regardless of the load on it ... thanks

[tim]

Dear Bill,

I'm not sure if this helps but, Volts x Amps=Watts. Therefore, since you are using a transformer and voltage is fixed, the only variable in the equation is the amp draw of the bulbs. Your old bulbs drew about .166 amps. Your new ones draw .0083. You could have 100 led's.

The Transformer is is just 2 coils, that transmit elec. magnetically as opposed to mechanically. There is no conductive connection between the circuits, which may be at arbitrary constant potentials. Only changes in one circuit affect the other. When a transformer is on, but no power is drawn, the draw is equal to the resistance of the coil. This is dissipated in the form of heat. There is some loss to the system due to the resistance of the coil material and the ferromagnetic material.

Long story short, your transformer will draw current at rest, but not 100 watts. Otherwise it will pull whatever amperage it needs up to its rated capacity (where there's usually a fuse).

BTW I'm not an electrical engineer so ne1 feel free to correct.

-tim

[Tiger]

The consumption drops 95 percent. The transformer only provides power according to the load of the system. Although there are some energy loss at the transformer due to the heat but it is a minor loss.

Just make sure the LED can handle 12V power or otherwise it is toast.

[Kalevera]

Good stuff! Wow, this makes me want to replace all of the interior lights in my car with blue high intesity LEDs.

[Bill R.]

the owner of a local lighting company was telling me that it would consume 100watts regardless of the load on it up to the maximum 100watts that the transformer was rated at...I have some low voltage halogen mr16 lights in my hallway that i wired up with a 100w transformer ,running the maximum allowed 5 lights at 20watts mr16 bulbs each, so in theory i'm lighting my hallway with 100watts total... lately i've been looking at some of these 1,2 and 3 watt led mr16 replacements that supposed to put out quite a bit of light with a very long bulb life.
So i thought i would try a couple out in the hallway and if they work well wire up a number of lights in my house with them and see if i can't drop my total power consumption a good bit..

The consumption drops 95 percent. The transformer only provides power according to the load of the system. Although there are some energy loss at the transformer due to the heat but it is a minor loss.

Just make sure the LED can handle 12V power or otherwise it is toast.

[danzee]

The owner of a local lighting company is patently wrong. What the other guys here are telling you is substantially correct. The transformer will draw some small current plus what is needs to support the load you put on the 12V output.
Just be careful how much you UNDERutilize it. The unloaded "12V" output voltage will be higher than the "12V" output when it is fully loaded. Since the automotive lighting is designed to withstand at least 14V , I don't think you will have a problem at all.
I assume you are going to put some kind of rectifier after the transformer. The LEDs will either burn up or give lsomewhat lower light output on AC. The rectifier will drop the voltage slightly as well so you'll be back near 12V.
If what you meant when you said "transformer" is really something that puts out 12V DC (power supply, then the rectifier is built in and you are good to go.

[Javier]

in the board are telling you the truth, transformer will pass only the required power, based on the load, and will draw from the system this power plus looses that won't ever be significant. Even more, with low load in the system, the copper loses in the windings will be very low, so transformer will also run very cool, yes voltage will rise almost to no load value, but doubt the transformer regulation (Vloaded-Vunloaded)/Vunloaded will be over 5%.

I'm curious. What are this LED bulbs you are talking about? Are them suitable for AC voltage (alternating current), as were the former bulbs? A LED is a DC component, current will flow only in one direction, and when it does, it will generate light and have a voltage drop of about 1.4 volts, on the other hand, they can not withstand too much reverse voltage. If you take an ordinary led, and put 12 Vac on it, it will fry immediately. Guess your LED bulbs are some kind of LED array, with both ways led's series so to use current flow in both directions (as AC means).

Your only requisite then, would be to be sure your new bulbs are OK for 12 Vac operation, and you can put as many bulbs as you want up to 100 Watts. Will expend only the installed wattage.

Javier

[Bill R.]

get to the luxeon 1 watt wide angle, that and the 3 watt are the ones i'm considering to replace some existing 20 watt halogens, I'm even thinking about buying some of these for a pv panel and storage battery system..
led mr16 lights

in the board are telling you the truth, transformer will pass only the required power, based on the load, and will draw from the system this power plus looses that won't ever be significant. Even more, with low load in the system, the copper loses in the windings will be very low, so transformer will also run very cool, yes voltage will rise almost to no load value, but doubt the transformer regulation (Vloaded-Vunloaded)/Vunloaded will be over 5%.

I'm curious. What are this LED bulbs you are talking about? Are them suitable for AC voltage (alternating current), as were the former bulbs? A LED is a DC component, current will flow only in one direction, and when it does, it will generate light and have a voltage drop of about 1.4 volts, on the other hand, they can not withstand too much reverse voltage. If you take an ordinary led, and put 12 Vac on it, it will fry immediately. Guess your LED bulbs are some kind of LED array, with both ways led's series so to use current flow in both directions (as AC means).

Your only requisite then, would be to be sure your new bulbs are OK for 12 Vac operation, and you can put as many bulbs as you want up to 100 Watts. Will expend only the installed wattage.

Javier

[Javier]

You will have a better huge advantage, LED lamps will produce quite less heat than former halogens, so ambient temperature will be cooler with this LED lights.

This is a handicap of the halogen lights in hot seasons.

What didn't see were references to lumen (light) intensity, how they compare to halogens? If comparable, fell soon halogens will RIP.

Javier

[Bill R.]

star V and its 5 watts and 120 lumens output. But from people i've talked to that have seen them they say that the 120 lumens number is misleading. that it actually looks like it puts out a lot more light than that to them
Luxeon site

You will have a better huge advantage, LED lamps will produce quite less heat than former halogens, so ambient temperature will be cooler with this LED lights.

This is a handicap of the halogen lights in hot seasons.

What didn't see were references to lumen (light) intensity, how they compare to halogens? If comparable, fell soon halogens will RIP.

Javier