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Light Bulb

Glenn Wilson

Apr 5, 2015
3
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Apr 5, 2015
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Hello Members,

Could someone please help me, I have a 240volt LED light that I only want to come on when mains voltage is reached in the UK that's 240 v AC, but what is happening, is when a lower voltage is applied say 190 volts AC the bulb is coming on but dimmer than when 240 is applied

Can some one tell me how to prevent the light coming on when voltages less than 240 V are applied, so what I don't want is the bulb coming on when lower voltages than 240 v are applied and when 240 is applied the bulb switches on at full brightness

Many Thanks

Glenn
 

Glenn Wilson

Apr 5, 2015
3
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Apr 5, 2015
Messages
3
Hello Alec

Thanks for your reply I have had a look at what you suggested they are to expensive they cost about £70.00 is there another way that is cheaper

Thanks

Glenn
 

ramussons

Jun 10, 2014
439
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Jun 10, 2014
Messages
439
Well, you need a voltage sensor that disables the LED from switching ON below a certain voltage. That's what
alex Chiu said.
You can make one or buy one. Making one will be <<< £70.00.
 

Glenn Wilson

Apr 5, 2015
3
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Apr 5, 2015
Messages
3
Thanks for your reply

Do you know of a kit I could buy for this purpose that I could build myself as new to electronics
 

duke37

Jan 9, 2011
5,364
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Jan 9, 2011
Messages
5,364
I would use a wall wart with AC output.
Rectify this to give a power supply for the circuit with a suitable time constant.
Compare this supply with a reference and drive a relay.
You will only be dealing with low voltage in the circuit so safe for a beginner.
 

Gryd3

Jun 25, 2014
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4,098
I would use a wall wart with AC output.
Rectify this to give a power supply for the circuit with a suitable time constant.
Compare this supply with a reference and drive a relay.
You will only be dealing with low voltage in the circuit so safe for a beginner.
That would be a great learning process. but sounds like it requires a second power supply.
If this is learned and understood there is no reason an almost identical circuit could be built into the light build or light fixture.
Regardless of the method used though, you MUST have some kind of circuit to detect the current voltage level and switch on when it has reached a set point. They can be bought or built, but great care should be taken when dealing with mains voltages.

Perhaps Colin can elaborate on his 3003 proposal. We wouldn't want you to begin hacking apart fluorescent light bulbs if this solution is not acceptable to you
 
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