Electronic Theory Question

[Rick Collins]

Does a small step down transformer, like the type used to recharge nicad batteries (120v down to 12v, 24v, etc.), consume energy when it is left plugged into the outlet even when the other end is left open (nothing being recharged)?

Do you leave the recharging unit for a cordless drill always plugged in if you are not recharging the battery?

Thanks in advance, Rick

[Stephen Gambrell]

The primary of a transformer(the side connected to the AC outlet)is an inductor, and will continue to draw current, albeit in the milli- or even microamp range. But it will "use power", even if only to keep the little LED lit. And I leave my screwdriver charger plugged in all the time.

[Donny Hinson]

Were it "just a transformer", the answer would probably be "NO". But as Stephen says, they do consume a minute amount of electricity, and generate a small amount of heat, as well. In some transformer applications (like doorbell transformers), transformers remain "powered up" for many years, and it poses no problems. However, there's more components in these chargers than just a transformer and an L.E.D., so I like to unplug my battery chargers when they're not in use. They do seem to last longer that way. <FONT SIZE=1 COLOR="#8e236b"><p align=CENTER>[This message was edited by Donny Hinson on 01 September 2002 at 06:51 PM.]</p></FONT>

[Keith Hilton]

Good answer Donny. Some transformers only contain a iron core with copper wire wrapped around the core. Other transformers may contain a lot of other things. Things like regulation devices,filtering devices, and in some cases switching devices. When possible, I personally try and turn off transformers when not in use.

[Rick Collins]

This information is very useful; many thanks to all. The controller for the lawn sprinklers and drip systems has a clock, so it must stay powered up all of the time (24v);___the others I'll unplug when not in use.

Rick