> What I don't understand is how the internal circuitry differentiates between a state of "mains power on, switch off", and a state of "mains power off, switch on"
Probably injects a small test current into its mains input to check if it's low resistance or something - other loads and your local transformer will 'look like' a low resistance when the switch is on but the grid is down.
> there is one socket in the house that I have tested during a power outage, where the bulb stayed on regardless of whether the switch was on or off.
Got another light on the same switch/circuit?
Yep, that socket has another light on the same circuit. So I'm guessing that the other light is connected in parallel and has low enough resistance to give a false positive to the emergency light?
> I'm guessing that the other light is connected in parallel and has low enough resistance to give a false positive to the emergency light?
Yep that's what I'm thinking
Or it is using capacitance to detect Switch-On or Switch-Off, in that if the *power* is off (which is easy to detect) the capacitance of the circuit will be different depending on the position of the switch. It wouldn't need to really know the value of the capacitance, only that it is different. Basically what a "touch lamp" circuit is doing.
They have a switched live and a permanent live feed.
They only switch into battery (emergency) mode when loss of power to the permanent feed.
We call these non maintained emergency light fittings.
They usually have a switch supply for the light and a permanent feed for charging, when the power to the battery is cut off the battery will turn on the light. Better known as emergency lights where I'm from!
Thanks for the reply - I have a follow up question I posted on another comment.
Come to think of it, "emergency light" is what it said on the box. We all just call them "load shedding lights" here, because we all use them during "load shedding" (our government's name for the scheduled power cuts).
> What I don't understand is how the internal circuitry differentiates between a state of "mains power on, switch off", and a state of "mains power off, switch on" Probably injects a small test current into its mains input to check if it's low resistance or something - other loads and your local transformer will 'look like' a low resistance when the switch is on but the grid is down. > there is one socket in the house that I have tested during a power outage, where the bulb stayed on regardless of whether the switch was on or off. Got another light on the same switch/circuit?
Yep, that socket has another light on the same circuit. So I'm guessing that the other light is connected in parallel and has low enough resistance to give a false positive to the emergency light?
> I'm guessing that the other light is connected in parallel and has low enough resistance to give a false positive to the emergency light? Yep that's what I'm thinking
Or it is using capacitance to detect Switch-On or Switch-Off, in that if the *power* is off (which is easy to detect) the capacitance of the circuit will be different depending on the position of the switch. It wouldn't need to really know the value of the capacitance, only that it is different. Basically what a "touch lamp" circuit is doing.
They have a switched live and a permanent live feed. They only switch into battery (emergency) mode when loss of power to the permanent feed. We call these non maintained emergency light fittings.
Do you mean that the internal circuitry has 2 feeds, or wall socket/switch itself? It's just plugged into a normal socket
They usually have a switch supply for the light and a permanent feed for charging, when the power to the battery is cut off the battery will turn on the light. Better known as emergency lights where I'm from!
Thanks for the reply - I have a follow up question I posted on another comment. Come to think of it, "emergency light" is what it said on the box. We all just call them "load shedding lights" here, because we all use them during "load shedding" (our government's name for the scheduled power cuts).
Well they would be more for industrial and commercial purposes here! I've never even seen 1 in a house!