Non maintained EM switching

[sparky in training]

Hi All

I was replacing some faulty fluorescent lights yesterday when I cam across one with an emergency light attached to it. It was non maintained as once I had isolated power it switched on. When I cam across this light I could see it was an afterthought as the original light was wired in old colors, red black and green for earth whereas the EM light had new colors.
Turned out to be a tricky job because the new light wouldn't fit where the old light was so I had to adjust things and trim conduit back etc. Ended up just using push connectors to rewire the fitting.

Anyway, my question was what causes this EM light to switch on when power is disconnected, it has a permanent live going to it to charge the battery, is there some sort of relay internally that allows the battery to take over and power the light? For that matter, do maintained EM lights have a relay that switches over to battery supply?

 

[Pete999]

Hi All

I was replacing some faulty fluorescent lights yesterday when I cam across one with an emergency light attached to it. It was non maintained as once I had isolated power it switched on. When I cam across this light I could see it was an afterthought as the original light was wired in old colors, red black and green for earth whereas the EM light had new colors.
Turned out to be a tricky job because the new light wouldn't fit where the old light was so I had to adjust things and trim conduit back etc. Ended up just using push connectors to rewire the fitting.

Anyway, my question was what causes this EM light to switch on when power is disconnected, it has a permanent live going to it to charge the battery, is there some sort of relay internally that allows the battery to take over and power the light? For that matter, do maintained EM lights have a relay that switches over to battery supply?

Emergency Lighting Explained - Mount Lighting - http://www.mountlighting.co.uk/emergency-lighting-types-explained/
Best description I could find

 

[sparky in training]

Emergency Lighting Explained - Mount Lighting - http://www.mountlighting.co.uk/emergency-lighting-types-explained/
Best description I could find

Thankyou, I will have a read

 

[Pete999]

Thankyou, I will have a read

A bit more
https://mountlighting.co.uk/wp-content/uploads/2015/01/Emergency-Lighting-Quick-Guide.pdf

 

[Dannyg8810]

The emg light has done what it's supposed to do ,you disconnected the power supply so the light went into emergency using the power from the battery's which the supply was charging

 

[sparky in training]

The emg light has done what it's supposed to do ,you disconnected the power supply so the light went into emergency using the power from the battery's which the supply was charging

I know that, my question was what internally causes it to switch allowing battery power to flow

 

[Pete999]

I know that, my question was what internally causes it to switch allowing battery power to flow

Probably all solid state electronics but basically a relay/sensor of some sort will be aware of a loss of mains electricity and switch over to battery power, on reinstatement of power the reverse happens and all is honky dory

 

[Dannyg8810]

I know that, my question was what internally causes it to switch allowing battery power to flow

I do apologise I misread your post

 

[Rpa07]

I know that, my question was what internally causes it to switch allowing battery power to flow

You'll find that answer on the 'electronicsforum.co.uk' - to me the answer will be - "I don't care as long as it does"!
We have got to a point in today's society where everything is thrown out, swapped out and renewed. The amount of useful stuff that is disposed of hurts me to look and quite often find myself keeping this bit or that bit 'just in case'.
Respect for your quest for nano learning but sometimes you have to jump fully in or ignore why and carry on!
Obviously my own views - we all have a passion for why certain things work but 'everything ' takes it too far.
I look at PCBs and just shake my head at the amazing ability man has to create something so small that is so powerful then I'll look through glass and i'm amazed at how laminated glass can still be so see through! You get me!
How I get so much work done, now that's a good question!