Why do lights dim

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I have 2 sets of 40 bulb xmas lights.
Both have a standard plug (no transformer) to supply them using a ring format (ie they are all in series).

When I plug them in they are very bright.

However for convenience, I removed the plug from one set, split the ring on the other and joined them together to create an 80 bulb circuit - and the brightness halved.

So:
- can anyone explain why
- are they likely to cause any problems (overheating for example).

Thanks
 
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The sets are wired in series. So for a 40 bulb set the lamps should be 6volts each (check this).

If you add a second set, this needs to be wired up in parallel to the first set. If you wired the second up in series with the first, you will halve the voltage through the lamps, that is why they halve the brightness.

DO check that the bulbs are 6volt. (It will be written on them)
If they are less than 6volt, then they will die long before the turkey goes in the oven.
 
The 230 volts ( mains voltage ) is shared equally among the series connected lamps.

With 40 lamps in series each lamp has 230 /40 = 5.75 volts

With 80 lamps in series each lamp has 230 /80 = 2.875 volts

There will be no problems with over heating as the lamps are running on a lower voltage hence lower powere per lamp.
 
You have now created a 480 volt series set but are still running them on 240 volts.

As a bonus the lamps will last for almost ever.
 
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Duhhhhhh.....

Obvious when you think about it :oops: - but at my age my apprenticeship training is a distant memory :rolleyes:

Thanks guys
 
Duhhhhhh..... Obvious when you think about it :oops: - but at my age my apprenticeship training is a distant memory :rolleyes:
You have two choices. If you're happy with the dim lights then, as has been said, there's no harm in what you've done and the bulbs may well last 'for ever', so you could leave it 'as is'. However, if you would prefer full brightness, you can just put the two sets of 40 in parallel (again using a single plug if you wish), and then play the annual "hunt the dead bulb(s)" game!

Kind Regards, John
 
Or compromise and put 60 in series - they'll probably be bright enough to be perfectly OK, they'll still get a useful life-extending voltage reduction, and you'll have a stock of spare bulbs.
 
Or compromise and put 60 in series - they'll probably be bright enough to be perfectly OK, they'll still get a useful life-extending voltage reduction, and you'll have a stock of spare bulbs.

That is a very good idea.
 
I always found a small diode in series is a good compromise. Effective voltage becomes 170v, though flicker becomes 50 Hz rather than 100 Hz. Not really noticeable though for decorative purposes. A 1N4007 in the plug does the job. Put one end in the L terminal and solder the other end to the wire removed from the L terminal.
 
Or compromise and put 60 in series - they'll probably be bright enough to be perfectly OK, they'll still get a useful life-extending voltage reduction, and you'll have a stock of spare bulbs.
Another gem from ban all sheds! Win win situation, festive cheers all round(y):D
 

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