Tried Osram LED 5W5 501 bulbs in boot lamps .... neither worked :(:(

[ZZZZ]

I would agree reversing lights are unlikely to be linked to Adaptive Brakes ... what I meant was I suspect having ILS and Adaptive Braking lights means its likely the whole lighting system is quite advanced i.e. its not a simple on off switch delivering enough amps to light a 5W bulb.
OK it might not throw the usual Canbus broken bulb messgae, but it sure is doing other things, not normally associated with a simple boot light!

The lights are monitored and actuated by the vehicle's SAM, it's not, strictly speaking, a CANbus function.

Boot light would have a pretty simple ON/OFF on contact, and OFF on timer algorithm, all handled by the SAM.

 

[ZZZZ]

.
The shunt resistor can be away from the bulb so the heat can be dissipated elsewhere.

This is indeed the best way - particularly for anything over 5W ... I've just completed these dual-function turn signal harnesses, as part of my little "back to OEM look with extra functionality" programme

 

[Submariner1]

LED's run cooler than filament bulbs because they're more efficient (I know you are aware of that).
Increase the current to the same level by using a shunt resistor and the same amount of heat will be dissipated.
The shunt resistor can be away from the bulb so the heat can be dissipated elsewhere.

Basically, amps causes heat though that statement is not entirely true.
e.g. pylons run at very high voltage to reduce the amps, if they ran at 240V and transferred the same amount of power (watts) from the power station, they would melt due to the huge amps.
Fuses blow because of amps (the fuse melts from heat).

So if my std. 5 Watt MB 5W5 bulb is as follows
Watts / V = I

I= 5/12 .. 0.416A
I= V/R , .. 0.416 = 12/R
R= V/I .... R = 12/0.416 ...= 28.8 Ohms

And if my new Osram 501 LED is 1W.
As Watts = V* I
Then. I= W/V
I assume its 1/12= 0.083 Amps.
If R =V/I then R= 12/0.083 = 144 Ohms??

Ooops this must be wrong, as I assumed there would be less resistance in the LED bulb, as they say you need to add a resistor to fool the Can-bus if you want to replace a std bulb with a LED. .?

Based on Ohms Law

I=V/R

V= I R

R= V/I

I assume its the charachteristics of a diode, verses the traditional resistance of a std. filament bulb.

Well the grey cells have deteriorated today ... certainly would not pass Physics A Level today!

 

[Submariner1]

The lights are monitored and actuated by the vehicle's SAM, it's not, strictly speaking, a CANbus function.

Boot light would have a pretty simple ON/OFF on contact, and OFF on timer algorithm, all handled by the SAM.

Thanks
Thats what I thought.
But As the rain stopped for 5 minutes, I went out to the garage, and brought in the 12v 7Ah spare alarm battery.

Both Osram LEDs work perfectly!

Oops not expecting that.
So they do work ... just not in the CL Class



So there is something on the CL 500 that does more than the time out.

Its obviously looking at this LED bulb, and thinking its out of tolerance [ either too low a ressistive load, or not enough amps, for it to be a std. 5W5, so shutdown.

 

[Submariner1]

there are no specs on the Osram site ...

 

[L John]

Ooops this must be wrong, as I assumed there would be less resistance in the LED bulb, as they say you need to add a resistor to fool the Can-bus if you want to replace a std bulb with a LED. .?

More resistance means less current flow, the LED is a higher resistance than an equivalent brightness filament bulb.
Less resistance allows more current flow, think of a dam resisting water flow.

The added resistor fitted to fool a canbus is in parallel to the LED, like a diverter around the dam to give equal flow overall.

 

[ZZZZ]

^^^ Perfect explanation!

It sounds as these bulbs are monitored, but instead of instrument cluster error alert, they just deactivated by the SAM, so get a pair of these, and you'll be fine:

https://www.ebay.co.uk/itm/222250070055

I bought them recently - fast delivery and seems pretty good quality, apart from the 501 socket - Mercedes ones got tiny locking lugs to 'click' in, so I will swap the dummy and active sockets around - I got a bunch of quality 501 sockets anyway

 

[L John]

^^^ Perfect solution!

 

[LostKiwi]

Only problem with shunt resistors is you lose the bulb failure warning.

Personally I'll stick with filaments as they do as designed.

 

[L John]

Me too in general but the OP question was for a boot light so no safety issues and worth doing if GLK's suggestion works... and no reason I can see why it shouldn't.

 

[Submariner1]

More resistance means less current flow, the LED is a higher resistance than an equivalent brightness filament bulb.
Less resistance allows more current flow, think of a dam resisting water flow.

The added resistor fitted to fool a canbus is in parallel to the LED, like a diverter around the dam to give equal flow overall.

Brilliant !
Now I totally understand, I had read elsewhere that LEDs had a lower resistance and therefore needed a resistor in series!
Obviously nonsense,
as even my Mickey Mouse example above proved the LED would have a higher resistance.
And therefore needs the resistor in parallel, to reduce the total resistance to a number close to the original MB 5W5 bulb.

So one uses the formula :-
To find R2 , where R 1 is the resistance of the new LED.
RT = R1 x R2 / R1 + R2

So if the normal 5W5 Has a resistance if 28 Ohms and
The new LED has a resistance of 144 Ohms

To make it work I need to find what R2 is, and put that in parallel!
I.e. to make a total resistance equal to the original bulb i.e 28 Ohms.
Thus
28 = 144 x R2 / 144 + R2

Just plugging in the LED meant
I= V/R
I = 12/144 = 0.083A
As opposed to 0.416A on the original bulb.

 

[Submariner1]

Only problem with shunt resistors is you lose the bulb failure warning.

Personally I'll stick with filaments as they do as designed.

Just wondered , if they or you calculated the parallel resistor, so that the total resistance was identical to an original 5W5 bulb.
Why would you lose the bulb failure message?
Or does the car look at both current and resistance? And if either one is out of spec it throws the warning.

Just interested, as not relevant for me per se, as mine doesnt have a bulb failure message for the boot, just this monitored shut down.

 

[LostKiwi]

Just wondered , if they or you calculated the parallel resistor, so that the total resistance was identical to an original 5W5 bulb.
Why would you lose the bulb failure message?
Or does the car look at both current and resistance? And if either one is out of spec it throws the warning.

Just interested, as not relevant for me per se, as mine doesnt have a bulb failure message for the boot, just this monitored shut down.

The detection works on the basis of current flow. When you use a shunt resistor the bulk of the current flows through the resistor not the LED so a blown LED isn't detected as current still flows.

 

[L John]

Brilliant !
Now I totally understand, I had read elsewhere that LEDs had a lower resistance and therefore needed a resistor in series!
Obviously nonsense,
as even my Mickey Mouse example above proved the LED would have a higher resistance.
And therefore needs the resistor in parallel, to reduce the total resistance to a number close to the original MB 5W5 bulb.

LED's are lower voltage than the filament bulb and so they need a resistor in series to reduce the voltage across the LED.
This resistor is built in so it becomes a 12V bulb.
That may be where the confusion comes from.
You can calculate R2 to fit a shunt resistor (the diverter or parallel resistor) and fit that but you also need to calculate the watts that will be used by the resistor, it uses most of the power as already mentioned by LW so it can be assumed to be 5 watts.
When I was doing my electronics course we had to calculate to the nth degree for exams but when it comes to reality, close is good enough as long as the component meets the minimum requirement.

I've not checked your sums as the simple way is just to buy one of the ready made units.
If I was doing this myself I wouldn't be doing sums as when buying a unit that's all been done already.

 

[Botus]

Only problem with shunt resistors is you lose the bulb failure warning.

Personally I'll stick with filaments as they do as designed.

First bit is an interesting point, depends how the resistor bit is made could easily have a circuit to do bulb warning (but they probably don't).

As for keeping stock bulbs that's a ridiculous solution. A dim yellow glow that does the square route of nothing. This is a bit like saying std halogen lights are acceptable in todays driving conditions. If halogens were remotely suitable you wouldn't half the drivers going round with a dead bulb one side and they are totally clueless its like that.

I support suitable upgrades of any bulb, for example if you want interior lights that allow you to see anything or reversing lights that actually illuminate behind the car, or in my case both that and give the rear camera an opportunity to show something other than pixelated black its a very good idea

 

[Submariner1]

The detection works on the basis of current flow. When you use a shunt resistor the bulk of the current flows through the resistor not the LED so a blown LED isn't detected as current still flows.

OK that makes sense.

 

[Submariner1]

^^^ Perfect explanation!

It sounds as these bulbs are monitored, but instead of instrument cluster error alert, they just deactivated by the SAM, so get a pair of these, and you'll be fine:

https://www.ebay.co.uk/itm/222250070055

I bought them recently - fast delivery and seems pretty good quality, apart from the 501 socket - Mercedes ones got tiny locking lugs to 'click' in, so I will swap the dummy and active sockets around - I got a bunch of quality 501 sockets anyway

I appreciate the link.
The only thing is taking out these relatively small bulb holders,
wont give you enough room to insert something 7” long.
And at that size / weight would need securing.

Yes I agree one would need something like this.
I would also prefer to use something made by a premium vendor, just in case it blew up the entire ILS !
Bet that would cost a forture to replace.

I saw 2 products from Osram
They looked like this
https://www.osram.com/appsj/pdc/pdf.do?cid=GPS01_2810559&vid=PP_EUROPE_Europe_eCat&lid=EN&mpid=


I think they are about 15mm long and 9mm wide.?? So might be easy to fit in.

LEDriving Canbus Control 5 W
LEDCBCTRL101 5W

LEDriving Canbus Control 21 W
LEDCBCTRL102 21

Sadly Osrams site didn't say how big they were? Just got some dimensions from a google pic.

I also liked the idea Osram had diffrent ones for 5W and 21W ... some on eBay said they did both??

I might get a set and see if they work, or if not successful, I will revert back to Osrams (Halogen) Cool Blue Intense +20% as a poor, but risk free substitute. Hopefully a bit bluer and slightly brighter.

 

[ZZZZ]

There's no need for this form-factor in your case, in fact it is counter-productive: it is meant to be fixed to a metal surface, and that would require door card removal.

All you need to do, is wrap the small black metal case in tesa or similar heat-resistant foam to prevent it knocking about, or use a 3M Dual Lock tape - there's plenty os space inside the bottom of the door card. In fact, the yellow resistor cases are larger, than the black ones:

BTW, all OSRAM is doing here is packaging the same [Chinese manufactured] stuff in pretty boxes - these are not precision items, like halogen or xenon bulbs. Also judging by the (very stingy on details) data sheet, both resistors are the same, so they just playing overkill on T10 type.

I'm all for overcomplicating things myself (well, perhaps, over-engineering) ... but then, there's overcomplicating, and there's way over overcomplicating, eh?

 

[Submariner1]

There's no need for this form-factor in your case, in fact it is counter-productive: it is meant to be fixed to a metal surface, and that would require door card removal.

All you need to do, is wrap the small black metal case in tesa or similar heat-resistant foam to prevent it knocking about, or use a 3M Dual Lock tape - there's plenty os space inside the bottom of the door card. In fact, the yellow resistor cases are larger, than the black ones:

BTW, all OSRAM is doing here is packaging the same [Chinese manufactured] stuff in pretty boxes - these are not precision items, like halogen or xenon bulbs. Also judging by the (very stingy on details) data sheet, both resistors are the same, so they just playing overkill on T10 type.

I'm all for overcomplicating things myself (well, perhaps, over-engineering) ... but then, there's overcomplicating, and there's way over overcomplicating, eh?

Not over complicated, just cautious; that link said it was
“Total length: approx. 17.5cm / 6.89" 501, T10”

Thanks for the image, clarifying their error.

 

[ZZZZ]

No worries.
The length quoted is exactly right though - it's about 17.5 cm as you can see from the pic