|
|
mudplugger
Member Since: 25 Feb 2006
Location: err... near Inglewhite, Lancs.
Posts: 89
|
FET's are Field Effect Transistors - also known sometimes as MOSFET if that's the type (Metal Oxide Silicon Field Effect Transistor).
The field-effect transistor (FET) is a transistor that relies on an electric field to control the shape and hence the conductivity of a 'channel' in a semiconductor material. FETs are sometimes used as voltage-controlled resistors, and are useful for controlling power accurately.
I've used them in high end Hi-Fi amplifiers and in controlling power from a solar array when in the desert and needing HF signals over long distances..
Hope it helps..
Muddy. From a two Land Rover household to one big FFRR...
Range Rover Vogue TDV8
Shogun SWB 4Work
Steyr M9094 Tractor
(Still a D3 fan though!)
|
 21st Aug 2006 6:48 pm |
|
|
fakesnake
Member Since: 30 Mar 2006
Location: Leicestershire
Posts: 281
 
|
Well what d'ya know.
Stop/tail bulb form garage round the corner weighs 8g
Same bulb from L/R weighs 10g
So perhaps that's the answer to S/T bulb longevity -we'll see. What really amazes me is that the human hand can detect the lighter bulb! Richard
|
| 22nd Aug 2006 8:33 am |
|
|
PCH
Member Since: 12 Jan 2005
Location: Anywhere but work
Posts: 812
 
|
Sorry guys to raise this topic again.
I finally got around to buying a pair of red LED lights to replace the blowing brake light globes. I bought them from an auto retailer in Australia called "Autobarn". They are replacements for 5W/21W bayonet light globes
My question is: I only bought 2 for the brake lights because they were AU$38 a pair and I didn't want to buy another pair for the lower lights just in case they didn't work well. They work fine and seem bright. The lower two globes (clearance/parking lights) now look too dull compared to the brake lights when the brakes are not on. I tried both LED's on one side to check how they looked and they both look very bright. I'm thinking about getting another pair but I'm worried when you have the lights on that there is not going to be much difference in brightness between the brake lights and the lower lights when the brakes are applied.
Should I buy another pair for the lower lights? What are your thoughts?
Thanks
Chris 2011 Discovery 4 (MY12) SDV6 HSE with General Grabber AT's, Traxide Aux Battery system, custom rear drawers and Autosafe half height cargo barrier
Gone - 2005 Discovery 3 TDV6 HSE
ARB Bull Bar, Warn 9.5XP Winch, IPF D/Lights, Cooper STT's, LR Raised Air Intake, Traxide aux battery system, custom drawers and half height Autosafe cargo barrier, Mitchell Bros 4x4 tow hitch
|
| 8th Sep 2006 12:34 am |
|
|
Gareth
Site Moderator
Member Since: 07 Dec 2004
Location: Bramhall
Posts: 26710
|
I have them top and bottom, and whilst there is less contrast between Brake light and Tail light, it is adequate. Nobody has rear ended me yet!
|
| 8th Sep 2006 9:05 am |
|
|
AN
Member Since: 26 Jul 2005
Location: Hungary
Posts: 327
  
|
I have them in the top and bottom, and I was too surprised by the difference in light strength between the tail and break light (too little I recon), but we have a huge 3rd break light on the top of the car which should help.
Also I recon there is more confusing to have two different strength of taillight + 3rd kind of strength when the break is applied.
I would go for 4 led bulbs.
Regards, AN LR D3 S Black, Auto TDV6
|
| 8th Sep 2006 11:47 am |
|
|
PCH
Member Since: 12 Jan 2005
Location: Anywhere but work
Posts: 812
|
Thanks for your comments.
I suppose I will get another pair then.
Chris 2011 Discovery 4 (MY12) SDV6 HSE with General Grabber AT's, Traxide Aux Battery system, custom rear drawers and Autosafe half height cargo barrier
Gone - 2005 Discovery 3 TDV6 HSE
ARB Bull Bar, Warn 9.5XP Winch, IPF D/Lights, Cooper STT's, LR Raised Air Intake, Traxide aux battery system, custom drawers and half height Autosafe cargo barrier, Mitchell Bros 4x4 tow hitch
|
| 8th Sep 2006 11:51 am |
|
|
DiscoStu
Member Since: 09 Apr 2006
Location: London
Posts: 11412
|
Thanks to all for the advice. R/H brake light blown after 7500 miles (thanks Slimer - wondered what you meant about swapping the lamps!!).
Bought some LED's from the shop mentioned in this thread - they look good, but a bit disappointed with the brightness of the brake light. There's quite a difference when compared to the normal lamp. Disco 5 HSE Lux
https://www.youtube.com/watch?v=peyiqaJrmMU
|
| 9th Oct 2006 9:19 pm |
|
|
Gareth
Site Moderator
Member Since: 07 Dec 2004
Location: Bramhall
Posts: 26710
|
Yes I agree with this, I have the led's and find the tail lamp very bright, and the brake lamp not much brighter. Is there another bulb type that may be better? I'm not too clued up on led's and the options.
|
| 9th Oct 2006 9:59 pm |
|
|
AN
Member Since: 26 Jul 2005
Location: Hungary
Posts: 327
|
I bought 4 LED lights 3 month ago, and I discovered that in the brake light places one bulb was totally burned out, in the other one only half of the leds were working. The leds in the taillight were working normally (all leds are on). I recon they could not handle the higher voltage in the D3.
Regards, AN LR D3 S Black, Auto TDV6
|
| 10th Oct 2006 1:11 pm |
|
|
JakobVels
Member Since: 11 May 2006
Location: Copenhagen
Posts: 223
|
Gareth wrote:Yes I agree with this, I have the led's and find the tail lamp very bright, and the brake lamp not much brighter.
How are they rated ?
I've seen some rated 40/130mA - which should mean 3 times the draw and 3 times the light when brake is aplied. (Im not an electrics engineer but thats what my common sense tells me).
A Standard bulb has approx 4 times the draw. (5w vs 21w)
A couple of questions for those using LED's allready...
Are you using white or red LED's for tail/brake lights ?
How "Red" is the light looking compared to original (plastic cover on) with your color LED's?
Do you have side LED's in the bulb or only backward facing. ?
Cheers
Jakob
|
| 10th Oct 2006 1:53 pm |
|
|
dylansdad
Member Since: 04 Apr 2006
Location: Solihull
Posts: 745
|
thats not necesarily true. an LED may be more efficient turning the energy into light vs a filament bulb which generates light and heat. Only way to know for sure is to find measured brightness for each and compare that. (normally a lux figure if its available)
(think about energy saving bulbs as an example....different technology I know, but 21W is ment to be equvalent light to 100W so less power doesnt always equate to less light. ) 2004 TDV6 HSE Auto Zambezi Silver
|
| 10th Oct 2006 2:11 pm |
|
|
simon
Member Since: 11 Jan 2005
Location: Shropshire
Posts: 18296
|
Good point DD 
The key advantage to LED's is their immediacy in lighting up and reaching full brightness faster than a traditional bulb.
Also they are far more compact to an array of LED's can be built into the same space and potentially offer a brighter light. Oh and designers love them for that same reason as it makes their designs look pretty
|
| 10th Oct 2006 2:24 pm |
|
|
10forcash
Member Since: 09 Jun 2005
Location: Ubique
Posts: 16534
|
Tungsten filament lamps are just about the least efficient form of lighting you can get, about 97% of the output is heat, so for a 21W brake lamp, just 0.63W is light output, LED's are close to 90% effecient (IIRC) but the real measure is Lumens/Watt output. As has been discussed before, LED's have a very narrow output angle, 20 degrees is the average so tungsten lamp replacement LED's need a 'cluster' including rearward facing LED's so as to utilise the reflectors giving the same output spread as tungsten lamps - which have a 360 degree output of light.
Another factor is the colour temperature of the light, tungsten lighting is pretty much in the centre of the visible spectrum whereas 'white' LED's are more towards the blue end, where human eyesight is less receptive at those wavelengths, the effeciency of the light is further reduced by filtering, in the case of brake lights, it would be better to use red LED's than filter white ones, this is because of the different chemistry (amongst other things) used to create the visible spectrum output results in a very narrow spectral spread, filtering out the unwanted colours will reduce the visible output dramatically.
|
| 10th Oct 2006 2:30 pm |
|
|
JakobVels
Member Since: 11 May 2006
Location: Copenhagen
Posts: 223
|
dylansdad wrote:thats not necesarily true. an LED may be more efficient turning the energy into light vs a filament bulb which generates light and heat. Only way to know for sure is to find measured brightness for each and compare that. (normally a lux figure if its available)
(think about energy saving bulbs as an example....different technology I know, but 21W is ment to be equvalent light to 100W so less power doesnt always equate to less light. )
You are right - but we're talking about 2 different things.
Youre talking the difference in lumens per watt - bulps/leds compared.
I am talking the difference in wattage for the taillight part and the breaklight part.
Bulbs are 5/21 W meaning that the draw=light (roughly) when hitting brake is approx 4 times (21 divided by 5)
Leds i am looking at draw 40/130mA meaning roughly 3 times more light when hitting the brakes (130 divided by 40)
Compared bulbs light up 4 times stronger when braking - leds light up 3 time stronger when braking. (explains why led's are percived by some of you to be less different in tal/brake light - it is less different in lumnes)
Cheers
Jakob
PS will go for the red ones based on tfc explanation
|
| 10th Oct 2006 2:51 pm |
|
|
