How are some electronics with toggle switches able to play a closing tune when off?

Most "power" switches these days aren't really power switches. They just pretend.

Sometimes you have to yank the power cord out of the wall to force a hard reset. Our cable box needs that once in a while, after it crashes.

Lots of scopes and such have a fake power button on front and a real AC power switch on the back.

Those electronic devices I mentioned have batteries.

Then they can still do tricks after the switch is "off."

What happens when I turn the switch off? What happens when turning it back on?

The devices are about like most TV sets with remote controls or many of the modern computers. The on/off swithch is just connected to a pin on microprocessor. It can do anything the processor is programed to do.

In you case it is programmed to play the recorded message and then go to the low power 'sleep' state.

A contact closes and applies a voltage to some internal solid state switch to activate the rest of the electronics. Most PC power supplies are done that way - the switch on the front of the case merely signals that you want it to switch on to some other electronics.

When you remove that signal the device powers off - or more accurately sits there waiting for the switch to be closed again. This can be done at essentially at microamp currents so that battery life is unaffected.

From: snipped-for-privacy@highlandsniptechnology.com

... and that's why my saloon CD-player eats 6W (6W !) from the AC line when switched off, I just measured it last week... I read that the average household standby power consumption is 60W, some nuclear power plants worldwide that could be switched off if we came back to actual mechanical power switches ;+).

Robert

Watts or VA?

or the "soft" switch is effectively in parallel with the on/off switch. The hard switch turns on the power the soft switch can keep the power on for a controlled powerdown sometimes hardware made so that the soft switch can only keep the power on for a limited time

Robert Lacoste ALCIOM - The mixed signal experts -

Clearly Watts unfortunately (measured with one of our company-designed Powerspy2 ;+) ) Robert

The controlling transistors can be configured as a FF where they are both off in the off position so that there is virtually no current flow other than the transistor leakage. A pFET power switch and an nFET on the power switch gate to control that. Drive the nFET gate from the pFET output with a high value pull down and a high value pull up on the pFET draws very little when on and virtually zero when off. To turn on either bridge either switch. To turn off either interrupt the nFET switch with a second nFET or use a resistor to prevent excess current and drive one of the gates to the off state with a second nFET or pFET.

or connect the switch to enable on the voltage regulator that's usually there, some are <1uA when disabled

Aka vampire power.

You read a lot of stuff. Power companies often put out little pamphlets about "vampire" power drain. Where do they get the info? I followed the trail once and it let to a government study that made some bogus assumptions producing an anomalous result which was then exaggerated by the various "handlers" until it turned into "vampires" sucking your electrical blood. My own informal estimate was much, much less power drain. Bottom line is if it isn't hot enough to feel, it's not using enough power to worry about, even times millions.

TVs sold in the US since 2013 use less than 0.5W when off. Even times the number of people in the US that's much less than a nuclear reactor. The power consumption of wall warts of various types use much less power when not charging or powering a device.

You can easily buy a device to show what your instantaneous usage is or in the UK have a smart meter that comes with a realtime display.

My own base load is a shade under 100W which includes, burglar alarm, emergency lights, cooker, microwave, other eToys, phone(s), router, clocks, radios, TV and hifi. Some are much better <0.5W than others 5W.

Why estimate when you can measure it directly with a clip on current clamp? Far too many things are just under 4W due to earlier legislation.

That might be true but TVs from the analogue to digital changeover era often had default settings to leave the set powered up so that the digital tuner was available for external VCRs to record from. I found one that drew 30W when nominally "off". Hidden in settings was a way to disable it. My PC sound system draws the same power irrespective of the state of its on/off switch which merely seems to switch a blue LED on.

Old style wall warts that run warm to the touch even when unloaded down the back of furniture are base load you can easily get rid of. If you get an Owl or similar you can typically shed 10% of base load without much effort just by finding which kit uses most power and putting it onto a smart switched supply so it goes off completely when not in use.

Some smart green power devices can be trained to recognise the remote signal for switching on the power hungry device that are isolating.

The voltage that goes in has still losses in transformers etc.

Groetjes Albert

I think most of what you wrote agrees with with I posted. TVs from the digital changeover era are few and far between now if for no other reason that people tend to have much larger sets now. That was quite some time ago. Even 2013 was 8 years ago and many sets have gone into the land fill.

I don't remember ever having a wall wart that ran warm to the touch when off. Pretty much anything in PCs are gone after five years. Electronics are disposable for most people. They get a new cell phone every time they renew their contract. There really is not enough dross out their to present the big power drain they talk about in the vampire pamphlets. It's really just PR stuff.