12 into 240? theoretically?

[ColJack]

ok, so purely theoretically here..

could you wire 20 x 12V halogen downlighters IN SERIES straight to 230V mains?

it works in my head in theory.. each lamp would get a 12V drop across it.. and is the same theory behind many xmas lights..
the problem being the obvious one of one lamp goes and they all go out..

 

[ebee]

corse yer cud.
if the current is up to the cct.

 

[ban-all-sheds]

3-4A...

 

[ericmark]

The start up current on a quartz halogen lamp is many times its run current and it is unlikely they would all take same current on start up and one would likely blow it would need 12 volt zeners across each lamp and even then unlikely to be correct voltage on each lamp so life would be very short.

 

[ColJack]

50W/12V = 4.2A ( rounded up )
20W/12V = 1.7A ( rounded up )

 

[sparkyspike]

1 Shepherd x 2 Sheepdogs = 54 sheep ( rounded up ).

 

[electronicsuk]

Although it would work "theoretically", in theory, there would be the potential for 230v across a 12v lampholder if there was a break anywhere in the series circuit. Furthermore, and also in theory, if a lamp or number of lamps were to fail short circuit then this could result in higher voltage than expected across other lamps in the circuit.

 

[Stoday]

They all must be the same power.

If you have 12V 50W lamps and replace one with a 12V 20W lamp, it will blow first because it will get 26V across it.

 

[ban-all-sheds]

1 Shepherd x 2 Sheepdogs = 54 sheep ( rounded up ).

http://www.youtube.com/watch?v=D2FX9rviEhw

 

[ban-all-sheds]

Although it would work "theoretically", in theory, there would be the potential for 230v across a 12v lampholder if there was a break anywhere in the series circuit.

If it goes open circuit there will be 0v across each lampholder.

if a lamp or number of lamps were to fail short circuit

Do they ever do that?

 

[ebee]

Ban, I think he meant , if it goes open cct then acrross that one lampholder there would be mains potential until such times as a replacement is made.
I might be wrong there though

 

[davelx]

Ban, I think he meant , if it goes open cct then acrross that one lampholder there would be mains potential until such times as a replacement is made.
I might be wrong there though

Come on guys, it depends on where the break is, doesn't it? (rhetorical question.) BAS is pulling electonicsuk up on his use of the word "anywhere".

Anyone who can't work out what will be at what potential in this circuit for any given fault should leave well alone as it's very basic stuff.

 

[electronicsuk]

Ban, I think he meant , if it goes open cct then acrross that one lampholder there would be mains potential until such times as a replacement is made.
I might be wrong there though

Indeed, I should have said there would be potential for 230v between a lampholder and earth.

 

[Spark123]

You'd also see 230v across the lampholder with the blown lamp, or across the lampholder should one lamp be removed from a healthy circuit.

 

[RF Lighting]

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