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| bear100 Member Since: 22 Mar 2010 Location: South Wales Posts: 1917   
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This will either satisfy you or blow your mind
https://www.evilmadscientist.com/2012/resistors-for-leds/  2016 Range Rover Autobiography 4.4 TDV8
2010 110 XS Utility 2.4TDCI 2010 Range Rover Sport TDV8 (gone) 2007 Discovery HSE TDV6 (gone) 1993 110 csw 200 tdi (gone) 1994 90 HT 300 tdi (gone) 1994 discovery 300tdi (gone) 90 hybrid 3.5 v8 (gone) Range rover bobtail 3.5 v8 (gone) |
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16th Jun 2020 9:23am |
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| discomog Member Since: 09 May 2015 Location: Notts/Lincs Border Posts: 2529  
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That's the sort of information you need to digest on a rainy day in lock down. As you say "mind blowing". Defender 90XS SW
Mini Countryman Cooper S Morgan Plus 8 |
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16th Jun 2020 11:34am |
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| bear100 Member Since: 22 Mar 2010 Location: South Wales Posts: 1917
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Its not to bad really, certainly for a rainy lock down day! 2016 Range Rover Autobiography 4.4 TDV8 2010 110 XS Utility 2.4TDCI 2010 Range Rover Sport TDV8 (gone) 2007 Discovery HSE TDV6 (gone) 1993 110 csw 200 tdi (gone) 1994 90 HT 300 tdi (gone) 1994 discovery 300tdi (gone) 90 hybrid 3.5 v8 (gone) Range rover bobtail 3.5 v8 (gone) |
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16th Jun 2020 5:49pm |
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| athelstan Member Since: 06 Aug 2019 Location: Kent Posts: 55 
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Stone me! Who wrote that, Stephen Hawking? 2015 90 XS Station Wagon Puma 2.2
2015 Morgan Plus 4 |
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16th Jun 2020 9:14pm |
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| macfrank Member Since: 05 Nov 2015 Location: somewhere in the north Posts: 1081  
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erm, well, that page is a complicated explanation for a simple calculation based on Ohm's law. And I think it may not be the right solution for the glowing LED. The linked page explains how to calculate a resistor so a standard LED wont blow the moment you switch it on. That's for just one LED as shown in the photos, not LED arrays like in the festoons. An LED wants about 2 Volts (simplified). Car has 12V. Way too much. The resistor (R) should "take" 10 Volts away, so the LED "gets" its 2V. Ohm's Law: R = voltage / current (simple, eh?  )
So we need to know the current the LED draws (you can look it up in a datasheet), let's say 20mA (0,020 Ampere) for an old-school red LED. R = 10V / 0,02A = 500 Ohms Done. (but don't do this at home, i.e. for higher voltages!!) (Why do we use the LED's current to calculate the resistor? Well, along a single "wire" there can be only one current, so it's the same for LED and resistor.) Unfortunately I don't have a solution for our glowing LEDs. 
Basically the reason is, I believe, that the AS10 which does the dimming was engineered to work with incandescent lamps. They need a higher current than LEDs, to start glowing. From here it would get more complex but I'll spare us mutual embarassment.
For me the bottom line was not to risk the life of my ALM ECU, experimenting around. And also not to buy other festoons (re "remortgage the house"  )
Instead I just don't use the "auto" switch position.  |
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20th Jun 2020 9:59am |
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| Martyn668 Member Since: 17 Mar 2013 Location: Cambridgeshire Posts: 135
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I fitted the ones from Fourby. Cheap as chips and plenty bright enough. Probably not as good as your Philips ones, but good enough for me. I know MUD UK also do one, which from forum views is apparently very good, but way more expensive than the Fourby option (which retains the original housing).
I bought a festoon from Ebay for my Honda. No fitting issues (except I bought the wrong size first time round - I had no idea they come in so many different sizes!) However, like you I have a front door light on a PIR on our house. It never goes out. Glows dimly 24/7 until someone comes to the door in the dark, and then it lights up fully. It's actually not a bad idea to have it working like that, certainly at dusk, although it wound me up at first. Supposed to be energy saving, but is it using 100% power even when it's only glowing dimly? |
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29th Jun 2020 4:35pm |
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| bear100 Member Since: 22 Mar 2010 Location: South Wales Posts: 1917
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i have these in mine and got to be at leat 8 years old now
And only cost around £2 
 2016 Range Rover Autobiography 4.4 TDV8 2010 110 XS Utility 2.4TDCI 2010 Range Rover Sport TDV8 (gone) 2007 Discovery HSE TDV6 (gone) 1993 110 csw 200 tdi (gone) 1994 90 HT 300 tdi (gone) 1994 discovery 300tdi (gone) 90 hybrid 3.5 v8 (gone) Range rover bobtail 3.5 v8 (gone) |
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29th Jun 2020 6:29pm |
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| macfrank Member Since: 05 Nov 2015 Location: somewhere in the north Posts: 1081
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Reminds me of an engineer on the tele who showed that the PIR electronics of some indoor LED lamps draws as much power as the LED itself - and he got furious about it.
In our camper Defender I sometimes use the "glow feature" to get in / out of bed. So, if you can't come up with a solution, just redefine the problem |
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29th Jun 2020 8:01pm |
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