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Old 2nd October 2012, 09:12 PM   #11
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The power source is typically rated to have a specific voltage (12v, for example). There is also a current limit for the source. If the device is well protected or if it has significant internal resistance, the voltage will not hold at the design voltage (12v in this example) and the voltage will drop. For a well protected supply, it may survive having a high current load connected to it. If it's not well protected and more current is drawn from it than it was designed to deliver, the supply could be damaged.

In a car, the source is the battery and/or charging system plus the wiring. It's not likely that you'll draw more than the battery or charging system can supply but the wires feeding the device (lamps here) need to be large enough and must be fused properly.
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Old 2nd October 2012, 09:58 PM   #12
NED 209 is offline NED 209  Ireland
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ahhh, cheers once again. so both devices are, im grasping at words here, - relative.

I used the example of the car lights, but it was a question floating around in my head for a while now. thanks for the info.

might i ask, what would be an example of a well protected supply? if you point one out I can read further on the matter.
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Old 2nd October 2012, 09:59 PM   #13
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Apart from current limits and power consumption issues, keep in mind the following, important detail when talking about lights/lamps:

Conventional (or halogen) incandescent bulbs dissipate roughly 95% of the supplied electrical power as heat. Though a higher wattage bulb may physically fit into your spotlight, the construction (housing, reflector, socket) may not be able to survive the significantly higher heat load!

Andreas
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Old 2nd October 2012, 10:47 PM   #14
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There are a lot of examples of a well protected supply. The simplest is the battery/wire with the proper fuse. If the circuit is overloaded, the fuse blows and no damage is done.

In more complex supplies, there may be several types of protection. A voltage regulator like THIS one has both thermal and over-current protection. A simple regulator can be produced with just a few parts. If you look at the internal schematic diagram for this regulator, you can see that it's much more complex.

Other supplies shut down or significantly limit their output until the load is removed or reduced to a safe level.

For better examples, you'd need to be very specific about the type of supply.
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Old 3rd October 2012, 12:07 AM   #15
NED 209 is offline NED 209  Ireland
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thanks Perry. i had a look at the link but ive a php exam in the morning so its not a good idea for me to go trying to soak in more info.. ill come back to it when things are quieter.

Rundmaus, do you know of any improved bulbs that i can fit in there?
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Old 3rd October 2012, 12:23 AM   #16
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One option that you should look into is LED. The newer LEDs can easily produce as much light as a 55w incandescent. They will generally use less current/power (depending on how many you use). They will, however, cost more for an equal amount of light output. You won't be able to use bare LEDs. High power LEDs need heatsinks. To get the best beam, you'll need a properly designed reflector.
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Old 3rd October 2012, 06:20 AM   #17
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sorry, those were fma figures. i didn't bother with graphs and such, just measuring current and voltage and used a small collection of mr16, and h3 bulbs in 20, 30, 50, and 55, for differnt arrangements. the biggest goal was to get 110w @ 13v+ for me. only really bothered checking anything below 8.xv.... not trying to pick a fight, but was just trying to illustrate the effect. perhaps greater with a pair of bulbs, but i don't really care. kind of dropped off on re-winding stators years ago, when my back got too bad to ride much.

Anyways, it will help a great deal to know exactly what you are working with. what are the fixtures? fog-lights? (description of housing size helps) h3 bulbs? mr16? 6y 6.35, or other base? home 12v accent lights? color temperature an issue? i've been dealing with just about all the different lighting out there for the past couple years, and led's can, by far, out-perform incandescent bulbs in efficiency. the good ones are going to cost you, though. you have to look at the lumen output, and many have a mcd rating, so you have to do the calculation to convert. the color temperature makes a big differnce. i usually go after 4700k, or close/under, and the actual appearance is more like 6-7000k. if the fixture is good enough, you might be able to sneak some hid bulbs in there. hid's are more temperamental, though. they need an initial "burn-in" period, take a few seconds to light up full, and can have a problem with voltage fluctuation. they, too, create a great deal of heat/ir output, so the fixture needs to handle it. led's also do create their own heat, and the limitations should be printed on the package.
next, what kind of power source are you really using? is it on some sort of orv, trailer, stand-alone home/rec use? what power supply? are you planning on charging the battery, and then using the setup remotely, just from battery power, like a sort of "lantern"?
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Old 3rd October 2012, 07:37 AM   #18
NED 209 is offline NED 209  Ireland
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hey there, havnt time to read your whole response, willdo later, saw the word color temperature, dont like blue light, warm white is good, amber like the old euro headlights is better.

came across this place last night, some intreresting threads, read one on leds, good stuff

HiDplanet : The Official Automotive Lighting Forum
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Old 3rd October 2012, 08:26 AM   #19
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Quote:
Originally Posted by AKHeathen View Post
sorry, those were fma figures. i didn't bother with graphs and such,[...]... not trying to pick a fight, but was just trying to illustrate the effect.


Didn't understand it as a fight, I just had a power supply, DMM and halogen bulb dummy load standing around in the lab, so why not measure it...

Could be that the effect is more exaggerated with a set of paralleled bulbs and such...

Andreas
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Old 5th October 2012, 05:59 AM   #20
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all good.
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