Simple wiring question, I'm 99 44/100ths % sure I'm right, but I have to ask

They'll be a bit happier off of AC.

Both, perhaps.

Best regards, Spehro Pefhany

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You know what... regarding that 56/100% that's not so sure... does anyone know how the resistance of a light bulb filament varies from room temperature to operating temperature? (All within one second, of course...)

Resistances could theoretically vary from light bulb to light bulb... theoretically this could kill some light bulbs prematurely... ???

When in doubt, run the experiment! (With full safety goggles...)

Michael

I would use low or high pressure sodium in reflectors with guards.

Things that will probably bring you unstuck:

1. Lamps in your series strings won't necessarily share the volt drop equally. Sooner or later - probably sooner - one will go O/C and the rest will extinguish.
2. Those lamps *may* go to 14v4, BUT in the automotive scenario the typical volt drop between source (that 14v4) and lamp is at least 1v. If you manage to get 14vanything at the lamps, their life will shorten - and see #1 above for the consequences of failure of one lamp in a series string. Careful selection of cabling will help drop the voltage at each lamp.

Sodium lights won't work because of three problems:

1. quality of light. I need it to be as white as possible.
2. physical size. Looking back, I didn't mention this as a requirement, but the bulbs and housings also need to be as compact as possible.
3. cost. Sodium lights ain't cheap. Not in the slightest.

Thanks anyway for the reply. I REALLY DO appreciate it.

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"Incandescent lamp resistance" on abse.

Fog lamps are suppose to have a shield in front of the lamp, so you don't see the lamp, and the coverage is limited. if it does not have this, then its not a true fog lamp. A driving or passing lamp does not have a shield in front of the lamp so coverage is bigger. A standard auto headlamp does have a shield over the low beam lamp, but not necessarily over the high beams. Small halogen lamps with sockets are prone to socket failure in the long run. Just try to get a lamp with a wide coverage preferably with a seald beam system. Think about total blackout when one fails.

greg

Spehro Pefhany a écrit :

How's that? Electronic wind? I remember an interesting report about aircraft incandescent lamps failure mode analysis used as some info source about aircraft crash... (I think it was you that posted this).

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Thanks,
Fred.

the

Maybe use nine. And you could rig up a second series that comes on automatically when the lights black out. Something as simple as a current transformer that holds a relay in the open circuit position: when the lights black out, current stops, the relay closes and the second series comes on.

They are also "assumed" to be in relatively free air and/or have an induced breeze on them from the forward speed of the vehicle. Don't put them into a hot box and expect them to last very long.

Bogey value for lead-acid "automotive" style power sources is 13.4 volts.

14.4 for very long will boil the battery dry. I'd use 9 lamps in series. If I wanted them to last forever, or if I was going to be switching them on and off a lot, I'd use an input surge limiter that could handle your four amps of steady state current.

Yes, probably.

Jim

Ah, the joys of the ambiguities of the English language!

By "off of AC", do you mean they'll be happier being powered by AC, or they'll be happier if they get off the AC like getting off the sauce, i.e., don't let AC near them?

I suspect you mean "running powered by AC", because the filament evaporation will be symmetrical.

Personally, I'd use more like 9 or 10 in series - 14.4 is probably pushing it for an incandescent.

And, of course, we assume that OP knows about double-insulation. :-)

Good Luck! Rich

...

They've been running series strings of Xmas tree bulbs for almost a century now. (not continuously, of course, I mean at Xmas, you drag out your series string of bulbs & stuff.) I don't foresee voltage-sharing as a problem - the one with the least resistance will, of course, drop the lowest voltage; they will reach equilibrium, much like series LEDs do.

Cheers! Rich

You could also use a low-voltage system, like those yard lights that you see all over the place.

The stumbling block, of course, is the cost of the transformer, and the need for really fat wire. At the transformer output, it has to carry ALL of the current for every bulb - 10X 4A bulbs would be 40 amps - #6 or #4 wire should be happy with that amount of current. Or, you could run individual pairs to each lamp.

Good Luck! Rich

The former.

Less notching effects, so the filaments should last somewhat longer.

Nature has a way of reminding us of such things every now and then.

Best regards, Spehro Pefhany

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"it\'s the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

Oh, yeah. I know all about double insulation. I don't like being shocked. At all. :-) ALL wires are routed through appropriate loom/ conduit and secured tightly, and whenever it passes through a metal hole, rubber grommets will be used. All final terminations are at an standard junction box. I'll put a 5A fuse in the box for good measure. By my math, this should present a total load of 440 watts equaling 3.82 amps).

The lights are only going to be used for a maximum of 10-15 minutes at a time, with 30 minutes to an hour rest between cycles. And they will only be used like that about once a month.

I was also thinking about making a 'burn out' indicator out by paralleling a 1156 bulb (21 watts) at each fog lamp. That way, if one goes out, it will probably take the 1156 with it, and it will be obvious which one died. Or I might get lucky and catch it before the indicator dies, a distinct possibility!

I was going to use 12 gauge wire, but now I am thinking of going to 16 or even 18 gauge to further increase the resistance. The total wire run will be about 70'. You think that will be OK, or should I stick to the 12?

I want to thank everyone who responded to my original post. All input is very appreciated, and will be put to good use!

Oh, yeah. I know all about double insulation. I don't like being shocked. At all. :-) ALL wires are routed through appropriate loom/ conduit and secured tightly, and whenever it passes through a metal hole, rubber grommets will be used. All final terminations are at an standard junction box. I'll put a 5A fuse in the box for good measure. By my math, this should present a total load of 440 watts equaling 3.82 amps).

The lights are only going to be used for a maximum of 10-15 minutes at a time, with 30 minutes to an hour rest between cycles. And they will only be used like that about once a month.

I was also thinking about making a 'burn out' indicator out by paralleling a 1156 bulb (21 watts) at each fog lamp. That way, if one goes out, it will probably take the 1156 with it, and it will be obvious which one died. Or I might get lucky and catch it before the indicator dies, a distinct possibility!

I was going to use 12 gauge wire, but now I am thinking of going to 16 or even 18 gauge to further increase the resistance. The total wire run will be about 70'. You think that will be OK, or should I stick to the 12?

I want to thank everyone who responded to my original post. All input is very appreciated, and will be put to good use!

Oh, yeah. I know all about double insulation. I don't like being shocked. At all. :-) ALL wires are routed through appropriate loom/ conduit and secured tightly, and whenever it passes through a metal hole, rubber grommets will be used. All final terminations are at an standard junction box. I'll put a 5A fuse in the box for good measure. By my math, this should present a total load of 440 watts equaling 3.82 amps).

The lights are only going to be used for a maximum of 10-15 minutes at a time, with 30 minutes to an hour rest between cycles. And they will only be used like that about once a month.

I was also thinking about making a 'burn out' indicator out by paralleling a 1156 bulb (21 watts) at each fog lamp. That way, if one goes out, it will probably take the 1156 with it, and it will be obvious which one died. Or I might get lucky and catch it before the indicator dies, a distinct possibility!

I was going to use 12 gauge wire, but now I am thinking of going to 16 or even 18 gauge to further increase the resistance. The total wire run will be about 70'. You think that will be OK, or should I stick to the 12?

I want to thank everyone who responded to my original post. All input is very appreciated, and will be put to good use!

Oh, yeah. I know all about double insulation. I don't like being shocked. At all. :-) ALL wires are routed through appropriate loom/ conduit and secured tightly, and whenever it passes through a metal hole, rubber grommets will be used. All final terminations are at an standard junction box. I'll put a 5A fuse in the box for good measure. By my math, this should present a total load of 440 watts equaling 3.82 amps).

The lights are only going to be used for a maximum of 10-15 minutes at a time, with 30 minutes to an hour rest between cycles. And they will only be used like that about once a month.

I was also thinking about making a 'burn out' indicator out by paralleling a 1156 bulb (21 watts) at each fog lamp. That way, if one goes out, it will probably take the 1156 with it, and it will be obvious which one died. Or I might get lucky and catch it before the indicator dies, a distinct possibility!

I was going to use 12 gauge wire, but now I am thinking of going to 16 or even 18 gauge to further increase the resistance. The total wire run will be about 70'. You think that will be OK, or should I stick to the 12?

I want to thank everyone who responded to my original post. All input is very appreciated, and will be put to good use!