electronics 101

[nyazzip]

it has occurred to me that maybe there should be a section in here for basic general electrnics questions/tutorials etcetera, that may or may not apply directly to tube circuitry.

anyway here's a question:

I have a low voltage transformer for powering some outdoor landscape lights. with LEDs these days, you don't need much, and this one is rated at 45 watts max output

120vac primary, 12vac secondary, 0.45amp
it is equipped with a photocell for automatic operation.

I intend to drive a only handful of 1-2 watt LEDs so the 45 watt rating will never be approached.

I noticed the transformer was warm to the touch during the day(in the shade). not hot, but noticeably warm. my question is, how much electricity might this thing consume during the day, when the lights are not in operation? I would like to waste as little electricity as possible, and I may install a switch


thanks

[azazello]

You can connect in serial with the primary tester in mode AC current and count....W=IxU....

[WA4SWJ]

All transformers are not perfect devices. Power transformers do have magnetizing losses in the core and resistive losses in the windings and are going to use some small amount of power during unloaded operation just to keep the core magnetized. The losses should be very small unless the transformer designer designed it so that the flux density in the core is high. The warmth you feel is the result of these losses, which should be small but are there nonetheless. If you're off the grid it might be a small concern but otherwise it would be a very low cost drain on your electric bill.

BTW - Why do transformers hum? They don't know the words! AWWWW - quick - duck!! Bad joke.

Best regards,

[20to20]

I have a low voltage transformer for powering some outdoor landscape lights. with LEDs these days, you don't need much, and this one is rated at 45 watts max output

120vac primary, 12vac secondary, 0.45amp
it is equipped with a photocell for automatic operation.

I intend to drive a only handful of 1-2 watt LEDs so the 45 watt rating will never be approached.

thanks

The usefull power available is in the secondary rating. About 6W a/c for incandescents if that .45A is for the secondary side. How many lights and what wattage is it driving now?

[DeathRex]

We used to get a wall wart transformer from Calrad to sell with our units. I found it used 6 watts off and 14 watts on. We now use Phihong switching power supplies for about the same price, but they use 1/4 watt off, and 14 watts on.