Series / Parallel circuit for light box


Postby nellyc999 » Tue Aug 05, 2008 3:46 pm

Hi there, I'm new here and fairly new to electrics (only 3 shocks so far!)learning fast and would appreciate any advice from some of the experts here.

I'm making 2 large ornamental wooden frames which will be lit using fair style lights (i.e. from a waltzer)
[b]
The bits I know.[/b]
I will have a 240V supply and will be using 60W SES Bulbs

1 frame will have 20 x 60W Bulbs
1 frame will have 24 x 60W Bulbs

I have made a much smaller frame before and used 1.5 tri rated cable and connected 7x60W bulbs in series on a 240V supply - so each bulb was getting approx 35W? Looks ok and I had to use 7 bulbs.

The next frames using 20 and 24 bulbs need to be brighter 40-50W

[b]The bits I don't know[/b] Can I use the same 1.5 tri rated cable and wire up groups of 4/5 bulbs in series, then connect each series back to the single main supply?

Should I add some kind of small fuse box to take each series back to?
If so what size fuses should I use? Where can I get a small fuse box (needs to be no greater than 3" x 3"

Any other ideas that might save me from burning the house down or further shocks?

Thanks
nellyc999
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Postby sparx » Tue Aug 05, 2008 7:31 pm

Hi Nellyc,
on your previous frame your bulbs (leckies call em lamps BTW, as bulbs grow in ground we are told at college!) thats just b4 someone gets picky.
Sorry, where was I? your bulbs each had 34Volts so to get a bit brighter you would need say 50V each, this means series of approx 5 as you suggest with 4 parallel sets on one frame & 4 sets of 5 plus one set of 4 in other frame.
your method is very good but please take care as 240v is a killer.Trirated singles @ 1.5mm2 will be ok for power used but only single layer of mechanical protection, can you use very small minitrunking to contain wiring?
Not much to go on but one fuse per frame probably ok, how are you powering them? from existing lighting cct, from socket via plug fuse?
There are term strips that go onto DIN rail which have inbuilt fuses made by Klippon who also do normal connectors for DIN rail, a 3" length of rail would hold say 4 fused, 2Neutral & 2 Earth connectors and would fit in 3X3 box fascinating project but PLEASE TAKE CARE we can't afford to lose people from Forum Hi! Hi!,
regards SPARX
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Postby nellyc999 » Tue Aug 05, 2008 9:00 pm

Thanks for the really quick reply sparx - appreciated.
Apologies for length of my reply - I've quoted you to answer all questions as fully as you answered mine.

I'll be calling them lamps from now onwards and will leave Percy Thrower terminology for gardners weekly - thanks for the tip

"your method is very good but please take care as 240v is a killer."

Great - I'm glad I'm on the right track with this -
Lessons will be very soon to avoid any future scares....

"Trirated singles @ 1.5mm2 will be ok for power used but only single layer of mechanical protection, can you use very small minitrunking to contain wiring?"

The frames are hollow so all cable and connections are out of sight and out of reach of my conductive fingers - though I will look to see if I can improve in any areas - another good practical tip - cheers.

"Not much to go on but one fuse per frame probably ok, how are you powering them? from existing lighting cct, from socket via plug fuse?"

The frames are going to be plugged via 13Amp plug and socket - Is 13A too high for safety? Is it worth a lower fuse for that extra safety?

"There are term strips that go onto DIN rail which have inbuilt fuses made by Klippon who also do normal connectors for DIN rail, a 3" length of rail would hold say 4 fused, 2Neutral & 2 Earth connectors and would fit in 3X3 box"

I will look in to these as I have some small space I could build this in to also. And will be useful in future projects.

"fascinating project but PLEASE TAKE CARE we can't afford to lose people from Forum Hi! Hi!,
regards SPARX

I will be taking extra care and asking when unsure - Thanks again for your help - really appreciate it! If you do have the time to answer my questions again, I would appreciate it greatly. And If I can suss out how to post pictures, I'll send some...one step at a time...

Thanx
Neil
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Postby sparx » Thu Aug 07, 2008 9:35 pm

Hi again, last point, 13A probably much too high for close protection, I would try a 3A first, if it holds good, if it melts/blows go up to a 5A,
I say do it this way as I presume you don't have any means of measuring the current drawn when built.
[1000Watts draws around 4A] so 13A would supply around 3000Watts-some light box!!!
You want the smallest fuse that takes the load without blowing, that may even be a 2A one, apply this principle to all future projects , fuses cost pennies and could save a fire!
good luck with projects, I wish I had time to dabble again, still am trying to cut back on work towards retirement so only doing a 4 day week when customers allow!
BW SPARX
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Postby nellyc999 » Thu Aug 14, 2008 8:33 pm

Sorry for long delay in replying, why does work get in the way of life so much...!

I went for the 3Amp and all ok - Thanks again for your helpful advice!

Thank you for your Good Luck wishes

Really appreciated your help.

Good luck with the retirement plans!
nellyc999
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