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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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#1
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Power an LED from a light switch?
Is it possible to power an LED from a light switch (live only connections,
and possible earth) so an illuminated LED can indicate if the light is on or off? |
#2
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Power an LED from a light switch?
In article , Pete
writes Is it possible to power an LED from a light switch (live only connections, and possible earth) so an illuminated LED can indicate if the light is on or off? Yup, fixed width font LED ----RES180R---||---- | | SWITCHED-FEED----||--||--||--||------LAMP | | ---------||--------- --||-- = DIODE A bit heavy on component count but lights evenly independent of lamp load, choose diodes to match full lamp current. LED is low current (5mA). All parts are live, including the LED. For safety don't poke the led thro the panel, use a plastic holder. Extra components would be required to meet BS/VDE safety. -- fred |
#3
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Power an LED from a light switch?
Pete wrote:
Is it possible to power an LED from a light switch (live only connections, and possible earth) so an illuminated LED can indicate if the light is on or off? Yes. Its horrendously inefficinet tho. You need a diode in addition to the LED wired in series, and a series resistor. about 22Kohms will do and at LEAST 2W rated. It will get hot. Alternatively a capacitor can be used, but tis late and I can't be bothered to calculate teh value..., |
#4
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Power an LED from a light switch?
"Pete" wrote in message ... Is it possible to power an LED from a light switch (live only connections, and possible earth) so an illuminated LED can indicate if the light is on or off? Why not use a neon lamp like the ones used in cooker units ? These don't have to be wired to anything fancy like diodes or heavy resistors. They are easily obtained and very cheap, and can be wired to live and earth if your not using an RCD breaker. It can be done remotely from one room to another, which I do quite regularly to indicate when water heater thermostats are switching on and off. Like these ones: http://tinyurl.com/hvnt --- www.basecuritysystems.no-ip.com Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.502 / Virus Database: 300 - Release Date: 18/07/03 |
#5
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Power an LED from a light switch?
"BigWallop" wrote in message ... "Pete" wrote in message ... Is it possible to power an LED from a light switch (live only connections, and possible earth) so an illuminated LED can indicate if the light is on or off? Why not use a neon lamp like the ones used in cooker units ? These don't have to be wired to anything fancy like diodes or heavy resistors. They are easily obtained and very cheap, and can be wired to live and earth if your not using an RCD breaker. It can be done remotely from one room to another, which I do quite regularly to indicate when water heater thermostats are switching on and off. Like these ones: http://tinyurl.com/hvnt Just thinking out loud here, but wouldn't the big GLS lamp in the middle of the ceiling, yes, the thing inside that light shade, tell you if the switch is on or off ? --- www.basecuritysystems.no-ip.com Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.502 / Virus Database: 300 - Release Date: 18/07/03 |
#6
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Power an LED from a light switch?
On Thu, 24 Jul 2003 04:18:25 GMT, "BigWallop"
wrote: Just thinking out loud here, but wouldn't the big GLS lamp in the middle of the ceiling, yes, the thing inside that light shade, tell you if the switch is on or off ? Damn. You spotted the ruse Andrew Do you need a handyman service? Check out our web site at http://www.handymac.co.uk |
#7
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Power an LED from a light switch?
"BigWallop" wrote in message ... .... Just thinking out loud here, but wouldn't the big GLS lamp in the middle of the ceiling, yes, the thing inside that light shade, tell you if the switch is on or off ? Perhaps it is to tell him whether the switch is off before he takes the blown GLS lamp out to change it? I've replaced all the filament lamps in the indicators on the machines in my factories with mains rated LED 'lamps', supplied with the same fittings. They are a lot dearer, but they are also far more reliable and the savings on maintenance (most take a disproportionate amount of time to change) covers the extra cost. Colin Bignell |
#8
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Power an LED from a light switch?
nightjar wrote in message
. .. "BigWallop" wrote in message ... ... Just thinking out loud here, but wouldn't the big GLS lamp in the middle of the ceiling, yes, the thing inside that light shade, tell you if the switch is on or off ? Perhaps it is to tell him whether the switch is off before he takes the blown GLS lamp out to change it? I've replaced all the filament lamps in the indicators on the machines in my factories with mains rated LED 'lamps', supplied with the same fittings. They are a lot dearer, but they are also far more reliable and the savings on maintenance (most take a disproportionate amount of time to change) covers the extra cost. Colin Bignell Possibly an indicator for a loft, attic, cellar or cupboard light.... Or perhaps it's to stop the electricity usage when the (unobserved) light is both off and on simultaneously (junk science meets Schroedinger) cheers Richard -- Richard Sampson email me at richard at olifant d-ot co do-t uk |
#9
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Power an LED from a light switch?
The Natural Philosopher wrote:
LED ----RES180R---||---- | | SWITCHED-FEED----||--||--||--||------LAMP | | ---------||--------- Thats quite neat. Not sure 4 diodes are good ebnough to light the LED tho. Maybe a power Zenert? That looks like it ought to put 13mA through the LED with a RMS forward voltage of about 2.4V which should be plenty. Must admit I did something similar for a "on charge" indicator in a constant current battery charger I built a while ago. I found I could actually get a decent light level out of the LED with only 3 series silicon diodes (even though by "design" it should have needed more). (although for this application I think I would just use a neon between switched live and earth - or across the switch if you want the neon lit when the switch is off) -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
#10
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Power an LED from a light switch?
In article ,
Pete wrote: Is it possible to power an LED from a light switch (live only connections, and possible earth) so an illuminated LED can indicate if the light is on or off? Do you want the indicator to be on when the lamp is on, or would on when it's off be OK? I think it's the former you want since you mention an earth. What the regs say about using the earth as a return for the tiny amount of current required, I'm not sure, as plenty of electronic equipment uses this method for RFI suppression. -- *Some people are only alive because it is illegal to kill. Dave Plowman London SW 12 RIP Acorn |
#11
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Power an LED from a light switch?
In article ,
John Rumm wrote: (although for this application I think I would just use a neon between switched live and earth - or across the switch if you want the neon lit when the switch is off) There are also mains LED indicators available for those who don't like neons and can't be bothered with resistors and diodes. -- *If you must choose between two evils, pick the one you've never tried before Dave Plowman London SW 12 RIP Acorn |
#12
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Power an LED from a light switch?
In article , The Natural Philosopher
writes Thats quite neat. Not sure 4 diodes are good ebnough to light the LED tho. Maybe a power Zenert? I should have said that a low current red led was intended, which will only drop about 1.5V, should give about 5mA pk. Power zener good & removes the need for the reverse diode, but I was thinking of cheap & easily available comps - none at maplin under 5.1V. . . . but RS do a 5W at 3.3V, so here it is for that option: Fixed width font LED --RES330R---||---- | | SWITCHED-FEED------------]|-------------LAMP ZENER LED - red, low curr ZENER - 3.3V 3W or greater eg http://rswww.com code 447-2061 3.3V 5W zener 49p + vat but sadly min order 5pcs. Suitable for use up to 250W load. -- fred |
#13
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Power an LED from a light switch?
John Rumm wrote:
The Natural Philosopher wrote: LED ----RES180R---||---- | | SWITCHED-FEED----||--||--||--||------LAMP | | ---------||--------- Thats quite neat. Not sure 4 diodes are good ebnough to light the LED tho. Maybe a power Zenert? That looks like it ought to put 13mA through the LED with a RMS forward voltage of about 2.4V which should be plenty. Mmm. If the LED is red, yes.... Must admit I did something similar for a "on charge" indicator in a constant current battery charger I built a while ago. I found I could actually get a decent light level out of the LED with only 3 series silicon diodes (even though by "design" it should have needed more). (although for this application I think I would just use a neon between switched live and earth - or across the switch if you want the neon lit when the switch is off) |
#14
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Power an LED from a light switch?
"The Natural Philosopher" wrote in message ... John Rumm wrote: The Natural Philosopher wrote: LED ----RES180R---||---- | | SWITCHED-FEED----||--||--||--||------LAMP | | ---------||--------- Thats quite neat. Not sure 4 diodes are good ebnough to light the LED tho. Maybe a power Zenert? That looks like it ought to put 13mA through the LED with a RMS forward voltage of about 2.4V which should be plenty. Mmm. If the LED is red, yes.... LOL !!! Must admit I did something similar for a "on charge" indicator in a constant current battery charger I built a while ago. I found I could actually get a decent light level out of the LED with only 3 series silicon diodes (even though by "design" it should have needed more). (although for this application I think I would just use a neon between switched live and earth - or across the switch if you want the neon lit when the switch is off) --- www.basecuritysystems.no-ip.com Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.502 / Virus Database: 300 - Release Date: 18/07/03 |
#15
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Power an LED from a light switch?
In article , John Rumm
writes fred wrote: (although for this application I think I would just use a neon between switched live and earth shame on you :-/ I doubt one neon will eat into your RCD leakage budget too much! ;-) The only component I'll fit between live & earth is a Y-class cap :-! /safety lectr :-) -- fred |
#16
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Power an LED from a light switch?
"fred" wrote in message ... In article , John Rumm writes fred wrote: (although for this application I think I would just use a neon between switched live and earth shame on you :-/ I doubt one neon will eat into your RCD leakage budget too much! ;-) The only component I'll fit between live & earth is a Y-class cap :-! /safety lectr :-) -- fred I Concur. --- www.basecuritysystems.no-ip.com Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.502 / Virus Database: 300 - Release Date: 18/07/03 |
#17
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Power an LED from a light switch?
The Natural Philosopher wrote:
Pete wrote: Is it possible to power an LED from a light switch (live only connections, and possible earth) so an illuminated LED can indicate if the light is on or off? Yes. Its horrendously inefficinet tho. You need a diode in addition to the LED wired in series, and a series resistor. about 22Kohms will do and at LEAST 2W rated. It will get hot. Alternatively a capacitor can be used, but tis late and I can't be bothered to calculate teh value..., This sounds similar to a concept I used for a fermentation cupboard thermostat. IIRC it employed the reactance of a polystyrence capacitor placed in series with an electrolytic capacitor across live and neutral, followed by a diode from their junction with another electrolytic from diode to neutral. I think it supplied about 12 Vdc to the temperature controlling chip. Does any of that sound fesible - and yes it is late here! Richard |
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