How does an LED globe with internal battery still operate on the regular light switch?

frankvw

frankvw

Well-Known Member
Joined
Aug 8, 2009
Messages
178
Reaction score
65
I have an LED globe with an internal backup battery. I note that when during power outages the regular light switch still manages to switch the globe on and off (when on it runs on its internal battery) even though there is no electricity. How does that work? Somehow the globe "senses" when regular light switch opens and closes even though there is no power. Hoe does it do that?
 
Minute amounts of current through the live and neutral legs of the circuit, like how a multimeter senses a closed or open circuit
 

It's pretty clever.

When there's no power, the difference between switched on/off is that with the switch on, the lamp can "see" the other devices on the circuit. In this case it stays on.

This is also why they don't work (incorrectly stay on) in some configurations e.g. where a switch controls multiple fixtures. They sense each other behind the switch and assume "their" switch is on. (I guess there will be cleverer ones that detect and handle the case where there are multiple of that same type of bulb behind a switch).
 
Last edited:
frankvw said:
I have an LED globe with an internal backup battery. I note that when during power outages the regular light switch still manages to switch the globe on and off (when on it runs on its internal battery) even though there is no electricity. How does that work? Somehow the globe "senses" when regular light switch opens and closes even though there is no power. Hoe does it do that?
Click to expand...
It sends some power out and sees if the loop is closed,and then with a logic gate - Power off + Loop closed = Switch to Battery Power
 
I have one which has gone into a failure mode where it never turns off even out of a fixture. It sits there with an eerie glow for days until it finally dies. That doesn't fix it. Give it a bit of charge and it stays on for another few days.
 
Tomtomtom said:
It's pretty clever. When there's no power, the difference between switched on/off is that with the switch on, the lamp can "see" the other devices on the circuit. In this case it stays on.
Click to expand...
Aha! Pretty clever indeed.
And I should have known that Big Clive would have found and reverse-engineered one by now so I do feel a bit stupid. :-)

Thanks!
 
Thanks for all the explanations everyone! It makes a lot more sense now.
 
Tomtomtom said:
I have one which has gone into a failure mode where it never turns off even out of a fixture. It sits there with an eerie glow for days until it finally dies. That doesn't fix it. Give it a bit of charge and it stays on for another few days.
Click to expand...

Haha, would like to see the expression on the Pikitup guy's face when your area has load shedding but your dustbin bag doesn't.
 
It uses capacitance.
The capacitance of the circuit with the switch closed is very different to the capacitance with the switch open.
 
I can even make mine work with putting my fingers on the contacts of the bulb, it detects a faint current obviously.

Does not work on multiple fittings controlled by one switch.
 
Sinbad said:
It uses capacitance.
The capacitance of the circuit with the switch closed is very different to the capacitance with the switch open.
Click to expand...

That ^

Capacitance of a closed circuit is 0, anything above this the light switches on. That's why you can do it with your finger and if you have some funky wiring somewhere it may detect "on" when it shouldn't.
 
I have 2 of these bulbs that I wanted to use during loadshedding. The one in the lounge works perfectly ie. during loadshedding I turn on the switch and the light works.

The one in the bathroom only works when the electricity is on even though both are identical bulbs. During loadshedding the bathroom bulb will not work. Even tried swopping the bulb to a new bulb.

Could it be something to do with the wiring in the bathroom? Extractor is also wired to same switch.
 
You must log in or register to reply here.
Back
Top
Sign up to the MyBroadband newsletter
X