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Candlepower to watts.

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    Posted: Apr/12/2019 at 2:14pm
While I have the cluster out, I'd like to replace the instrument bulbs with leds.
 
The TSM lists the output of the type 57 bulb as 2 candlepower. The might of Google can't tell me what that is in watts.
I don't want a bulb that's too big and dazzling.
 
Does anyone know?
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 304-dude Quote  Post ReplyReply Direct Link To This Post Posted: Apr/12/2019 at 2:27pm
Cant be calculated. Watts is measurment of electrical power over resistance, candle power is a measurement of light generated by free electron emittion.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Budwisr Quote  Post ReplyReply Direct Link To This Post Posted: Apr/12/2019 at 4:29pm
T57 is about 3.3 watts


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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: Apr/12/2019 at 7:26pm
Originally posted by 304-dude 304-dude wrote:

Cant be calculated. Watts is measurment of electrical power over resistance, candle power is a measurement of light generated by free electron emittion.



???

LOL, sorry, photon emission, not electron emission. No electrons are emitted.  Not with light bulbs, anyway. 

Watts is volts times amps. So a 3.3 watt bulb uses about a quarter amp (depending on the voltage measured at)

And there isn't really a direct correlation as far as watts to candlepower - even in standard home bulbs. I can show you 75 watt bulbs that put out a lot more light than others rated at the same wattage. 
You'll find that with LED, too - watts doesn't equal light output.
You are far better off dropping the candlepower as that's an old method not very scientific and not great for comparing light - go by luminosity. (Lumens)
That's far superior - and it's more accurate to compare. That's how folks are comparing to get LED replacements these days.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 6PakBee Quote  Post ReplyReply Direct Link To This Post Posted: Apr/12/2019 at 8:47pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 990V8 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/13/2019 at 3:36am
Mmm, thankyou.
 
I did read that candlepower as a measurement was 'obsolete' by 1948 so it's strange that it's still quoted in AMC's 1963 tsm.
Rock have a T57 bulb, but annoyingly they don't quote the wattage.
 
I'm cautious about leds. I have them in my side repeaters and in the front sidelights, where their brilliance is welcome, but I have a main beam warning light in my Land Rover which is so bright that it ruins my night vision and I've had to put a cover over it.
If you've ever removed the cluster, you'll know that it's a job you don't ever want to have to do again.
 
Note: I have been made aware of another problem with leds; the original dimmer is designed for a much higher load, so the tiniest twiddle and the leds will go out.
I can buy a dimmer for leds but iirc the dimmer also dims some courtesy bulbs?? so I'd need to change them all and get into the wiring.
Sigh.....
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bigbad69 Quote  Post ReplyReply Direct Link To This Post Posted: Apr/13/2019 at 9:28am
Candlepower is a measurement of luminous intensity
Watt is a measurement of power.
There really is no correlation between the two.

Candlepower is an obsolete term, but still seems to be used for very bright lamps such as aircraft landing lights. The accepted unit for luminous intensity is C/m2 (Candela per metre squared). This unit is also called the NIT (primarily in the US). The terms are interchangeable.

Historically, incandescent light bulbs have been spec'd by power (Watts). While technically wrong, the bulbs were all manufactured similarly such that all 40W bulbs gave off about the same amount of light. So the convention of selling 40W, 60W, 100W bulbs worked because people had a feel for the brightness while using these terms.

LED bulbs require much less power than incandescent bulbs to achieve the same brightness, which throws the whole system out of whack. Different processes in manufacturing LEDs mean the power to achieve a specific brightness can vary from LED to LED. You need to compare the actual brightness of incandescent vs LED to get an equivalent replacement. Household LED bulbs are often labeled as "equivalent to xW" just so you know what you are buying. Some judicious Googling can find brightness spec's for both the incandescent bulb being replaced and the replacement LED.

Dimmers for incandescent bulbs don't work properly with LED bulbs because the dimmers are simple variable resistors (automotive application). These resistors are much lower in value for incandescent vs LED. A mixed circuit of incandescent and LED bulbs cannot be controlled effectively with this kind of dimmer.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 990V8 Quote  Post ReplyReply Direct Link To This Post Posted: May/25/2019 at 4:58pm
Thanks. Guess the cp rating in the TSM was a hangover from days gone by.
 
In the end, I ducked out. As commented, would have had to change the original dimmer.
Most of the problem was burned bulbs, and the two bulbs that hang off the side of the cluster, the clips had fallen off so they were illuminating nothing.
 
What a pig of a job, getting the cluster out.
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 6768rogues Quote  Post ReplyReply Direct Link To This Post Posted: May/25/2019 at 6:35pm
Some building codes require exit lighting to provide at least one candlepower one foot above the floor, so the term is old but not forgotten.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote billd Quote  Post ReplyReply Direct Link To This Post Posted: May/25/2019 at 7:02pm
bigbad explained well - but here it is broken down a bit, maybe.....

if you’re looking for an energy-efficient light that illuminates a large area, consider lighting with a high lumen rating.
if you need a light that provides an intense beam, you should consider a light source’s candlepower instead.
That's one explanation I found on a site that sells lights......... 

they are measured differently - and how the light is focused or how is spreads will help mess up any conversions.

Narrow-beamed lights of all sorts can have very high candlepower specifications,
because candlepower measures the intensity of the light on a target, rather than the total amount of light it emits.
A given lamp has a higher candlepower rating if its light is more tightly focused.

If you are talking LED - they typically emit lumens more usable by the human eye. There's enough difference that they are looking at measuring light differently now - taking into account that an incandescent light that puts out xxx lumens may not SEEM as bright an LED that is rated at LESS lumens but it's more usable by the human eye.

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