DC Lighting

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I'm making some marquee-type light-up letters like this:http://bit.ly/2avcDhJ.

I'll be using a DC current with little MES bulbs like this: http://bit.ly/2aKpIVr (table of current/power/voltage at bottom of the page). Want the highest wattage ones practical and all bulbs to be the same.

There'll be five letters with the following number of bulbs:
1. 29
2. 25
3. 19
4. 19
5. 11

I'm wanting to use the most powerful bulbs that would be practical in terms of powers supplies etc. Guess they'd be wired in parallel like attached image. Would preferably wire them off one power supply but could split them into two. Guess I'll have to add resistors on the four lines with less than 29 bulbs to make the total resistance the same on each line but I'm basing this on an incredibly hazy memory of GCSE science/technology!

On second thoughts, if it's gonna be a lot easier I could just do five separate circuits and power supplies. Use the same, say, 12V supply but stick a resistor in the four smaller circuits. In any case would the bulbs themselves be wired in series or in parallel?

Anyway, if this doesn't make the slightest bit of sense feel free to ignore it. I have a headache.

There's a tenner in it (Paypal or summat) if anyone fancies coming up with a practical solution.

13920420_10157276994590051_4572380621220175863_o.jpg
 
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Any reason you wish to use filament lamps instead of LEDs?

If you ware planning on doing this as a number of series strings, all in parrallel with each other, is there any reason the strings cannot span the spaces between the characters, as you have a (29-11) 18 lamp difference between some letters, using a resister to drop the same volatage as 18 lamps would be wasteful, hot running and probably expensive. If you took the 1.5v 150mA lamps on the top of the data sheet (why does the link come up with bookface first before it goes to the rapid site?) you'd have to drop 1.5vx18 = 27v and at a current of 0.15A this with dissapate (0.15x27) just over 4W ! You could use different volatage lamps in each string, but you'd have to be careful not to muddle them up! If using LEDs, dropping the excess should not too wasteful as long as you pick a sensible design!
 
Thanks for your reply, Adam!

Just think it's gonna look a lot better with more traditional lamps. LEDS might look a bit 'school project'!

No they can run as a string no problem. Problem with those top lamps is that they're only 0.3W which isn't gonna be very bright at all. Even with 104 of them that's only 31W which isn't really gonna be bright enough for me. Will there be no way of incorporating 1-3W bulbs without large cabling?

Will change that bookface link (I posted this to some mates on FB before I posted it here!).
 
For my daughter's wedding I hung 372 lamps from the ceiling as 12 strings of 31 lamps each.

I
t and e on the dance floor.jpg


There is no need for balancing resistors but if the length of cable from supply to individual letters is more than a few metres then voltage drop needs to be considered.

A single heavy conductor from the supply to a distribution panel with 5 fuses close to the letters will means the viltage drop along the supply is common to all lamps.

V-drop lamps.jpg


The lamps I used were Barthelme 00211502 Dial Lamp E10 12-15 volt 10 x 28 mm From Rapid Electronics
The power unit was a single transformer feeding 12 individually switched and fused outlets.

If you have AC available then the lamps will last longer on AC supplies. Barthelme lamps are very good quality.

When the lamp is cold the resistance of the lamp is much lower than when the filament is glowing white. Hence when switching on there is a higher than normal current, therefore the fuses need to be slow blow devices.

If running on a transformer then the in-rush current has to be considered when selecting the fuse for the mains.

They give a very good light at 9 volts on the lamp. In the evening the room was lit only by the 372 lamps at circa 9 volts and they gave plenty of warm light ( when the Disco was not operating ). If running from a battery then do fuse the feed from the battery as well as a fuse for each letter.
 
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If you want lamps in the range of 1 to 3w then yes it can be done, but you have to realise that with 104 of them the wattage will be 104w - 312w.... now that is a fair bit of heat... what is the sign made of and where will it be positioned?
 
Cheers dudes,

I'm gonna read through that, Bernard, in a couple of hours when my heads a bit clearer!

Adam, they're gonna be in a shop window display. Open fronted letters on plywood so quite a lot of air circulation.

I was thinking i'd rather allow for the higher power bulbs but then have them on a dimmer so I can adjust it depending on what looks best when it's in there (or keep it permanently low-ish if it's getting too hot). Also thought if I turned on using a dimmer every day it would be less likely to blow bulbs. A lot of my house lights are on rotary dimmers and I've barely ever had to change bulbs whereas others I know are using the same bulbs and have them regularly blow on a normal on/off switch. That may br a bullshit theory, I don't know!
 
Rather than mess around with a dimmer (you'd either have to use a transformer compatable one) which could probably lead to the transformer being quite noisy. Or dim on the ELV side (which would probably need something custom making to do it)

You'd be simply better under running the lamps... eg. use a 3.2v lamp on a 3v supply. One must rememeber though that lamp life/ efficency is a trade off, whatever you do, dimmer ot under running, you get less lumens per watt when running at less than they are designed for. You occasionly here a story of a lamp over 100 years old, still working today and invariably they are very dim. Its not particulay amazing, these days we could easily make a lamp that ran forever, it would just not be effcient. They do however make long life lamps/rough sevice which use that trade off a little bit and are designed for either high stairwells were it is difficult to change them, or lamp lamps where they re shaken about
 
Okay, so I'm a little confused. If I was to run these on AC for bulb life at 12V then 104 Bulbs at 2W is going to be 208W or 17A to the junction box then:

Line 1: 29 bulbs = 58W
Line 2: 25 bulbs = 50W
Line 3: 15 bulbs = 30W
Line 4: 15 bulbs = 30W
Line 5: 11 bulbs = 30W

Also, 12V 200W AC Adators/PSUs don't seem to exist. Only DC. So is it okay to going back to 12V DC supply 200W (like this: http://bit.ly/2aLQCuh or can you recommend one?) to junction box then five unequal branches? So what cable size would be needed for 58W branch and what size for 200W to JB?

Will only be a metre to junction box then then maybe a metre tops to each letter.

unspecified.jpg
 
Use a transformer similar to this

Vigortronix VTX-126-200-612 Chassis Mains Transformer 200VA 0-12V from Rapid Order code 88-3734

fit it in a suitable box with ventilation and protection of the mains wiring.

Other sources for the transformer may be cheaper. Consider getting one with a multiple tapped secondary ( output ) to give the option of altering the voltage. ( or multiple tapped primary which may be cheaper )




 
Sweet. So that VTX box then a 2.5mm cable ??? diameter to junc box then five lines of ??? diameter cable wired in parallel.

Does that not mean each branch will only get 12/5V = 2.4V? Sorry for being dense.

Also, if I was going to fuse each line, what sort of fuse would I use?

I can't believe how helpful you're being by the way. Awesome.

2016-08-07 15.11.36.jpg
 
Sweet. So that VTX box then a 2.5mm cable ??? diameter to junc box then five lines of ??? diameter cable wired in parallel

16/0.2 wire would be adequate from transformer to each letter. Rapid 01-0940

7/0.2 wire from each lamp. Rapid 01-0435

Does that not mean each branch will only get 12/5V = 2.4V? Sorry for being dense.
No each lamp will be getting 12 volts

Also, if I was going to fuse each line, what sort of fuse would I use?

A 20mm fuse slow blow fuse in a holder. Depending on how you assemble the letters it could be a panel fuse holder Rapid 26-1578 but check the thickness of the panel or an inline holder Rapid 26-1583

For the wedding lights I used this method of connecting the wires from the lamps ( 7/0.2 ) to the "ring main" wires (16/0.2 )

Drop joint before assembly.jpg Drop joint assembled.jpg

The 300mm lengths would not be 300 mm but would be the distance between lamps. Using a fexible tails to the lamp holder makes the assembly much easy. Maybe you could take all the tails from a letter to a pair of terminals and not use a ring in the letter.

I can't believe how helpful you're being by the way. Awesome.
No problem sharing the design work done for the wedding if it helps someone
 
This is ace!

Just one more thing: all the 20mm glass slow blows are 250V rated.

With these powers...

Line 1: 29 2W bulbs = 58W / 250 = 0.23A
Line 2: 25 2W bulbs = 50W / 250 = 0.2A
Line 3: 15 2W bulbs = 30W / 250 = 0.12A
Line 4: 15 2W bulbs = 30W / 250 = 0.12A
Line 5: 11 2W bulbs = 22W / 250 = 0.09A

Is that the right working? So should I use all 0.5A/500mA fuses?
 
Line 1: 29 2W bulbs = 58W / 250 = 0.23A

Line 1: 29 2W bulbs = 58W / 12 = 5 Amp so use a 10 amp fuse ( for the inrush current when switching on ) The cable can carry 11 amps so if there is a fault the fuse will melt before the cable

Use 10 amp for all the lines

The 250 volts rating for the fuse is the maximum voltage the fuse can safely disconnect if it has to blow.
 
You, sir, are amazing. I offered a tenner at the beginning and I'd be delighted to send you it. Wanna PM me your email address for paypal-ing?
 

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