Lic Plate Light LED upgrade

[///Sniper535]

I found a pair of LED bulbs that fit the connection but I get the "LIC PLATE LIGHT" out message on the CC. The bulb size says 6461, i know it's not the exact match but does that have anything to do with it or the fact that it's an LED and not a bulb?

[Tiger]

They reads the resistance... do you get the message when you turn it on before you start the car?

[///Sniper535]

when i turn on the lights

[Tiger]

Then it senses not enough current being drawn.

[bad_manners_god]

Put a 1 Ohm Resistor in the circuit...problem solved.

[///Sniper535]

on each one?

[sal_park]

on each one?

yes, kinda. Here's my take:

I assume the standard licence plate lights are 5w each and the LED ones are 1w each.

Watts
------ = Amps
Volts

Volts
----- = Resistance
Amps


for the standard lights:

5W
--- = 0.41 A
12V

12V
---- = 30 ohms
0.41A


for the LED lights:

1W
--- = 0.08 A
12V

12V
---- = 150 ohms
0.08A


So now we need to make the 150 ohms resistance LED light look like it's only got 30 ohms resistance, by as bad_manners_god said put a resistor in the circuit. After a quick calculation we can see that the resistor should have a value between 35 - 40 ohms, NOT 1 ohm !

(have a look here (http://www.1728.com/resistrs.htm) for more details)

The resistor needs to be in parallel (http://en.wikipedia.org/wiki/Parallel_circuit#Parallel_circuits) with the LED light, 1 resistor per light:

hth


sal

p.s. it dosen't matter which way around the resistor goes

[sal_park]

Just done a quick google and it seems that the closest standard value is 47 ohms, available via your local maplins (or similar)

[pingu]

Good work with the sums, but I reckon that 33 ohms (which is also a standard resistor value) is probably closer to the notional 30 ohms of the 5W normal bulb.

Something to watch out for is that you'll relatively high power resistors. Normal "small" resistors can handle about 0.5 of a watt.

A 33 ohm resistor will dissipate about 5W, so you'd need a resistor rated to handle a power of a least 5W, preferably 10W so that the critter isn't on the edge of existence.

[sal_park]

fair point about the power

[GoldenOne]

yes, kinda. Here's my take:

I assume the standard licence plate lights are 5w each and the LED ones are 1w each.

Watts
------ = Amps
Volts

Volts
----- = Resistance
Amps


for the standard lights:

5W
--- = 0.41 A
12V

12V
---- = 30 ohms
0.41A


for the LED lights:

1W
--- = 0.08 A
12V

12V
---- = 150 ohms
0.08A


So now we need to make the 150 ohms resistance LED light look like it's only got 30 ohms resistance, by as bad_manners_god said put a resistor in the circuit. After a quick calculation we can see that the resistor should have a value between 35 - 40 ohms, NOT 1 ohm !

(have a look here (http://www.1728.com/resistrs.htm) for more details)

The resistor needs to be in parallel (http://en.wikipedia.org/wiki/Parallel_circuit#Parallel_circuits) with the LED light, 1 resistor per light:

hth


sal

p.s. it dosen't matter which way around the resistor goes

you wouldnt happen to know the threshold that the LKM sense to throw the circuit?

[sal_park]

you wouldnt happen to know the threshold that the LKM sense to throw the circuit?


No idea I'm afraid. Also I think the above posts(s) I made may be irrelevant - my front side lights are LED but I don't get any warning chimes for the side lights.

[Qube]

Yep. We've talked about this before. What's more important, my license plate lights or parking lights? :)

LEDs (white) in lic plates look good... as long as you can stand the warning, or wire up a resistor pack to it.

In the e39, at least it goes away after you start the car. On the e34, it just sit there, mocking you.

[///Sniper535]

Yep. We've talked about this before. What's more important, my license plate lights or parking lights? :)

LEDs (white) in lic plates look good... as long as you can stand the warning, or wire up a resistor pack to it.

In the e39, at least it goes away after you start the car. On the e34, it just sit there, mocking you.

Where do you wire up the resistors? Do you have pics of you car with them on?

[bad_manners_god]

Red is Positive, Black is Ground

http://i252.photobucket.com/albums/hh25/badmannersgod/resistor.jpg

[///Sniper535]

Will those "XENON" 6418 bulbs light up as well as the LED ones?

[bad_manners_god]

Will those "XENON" 6418 bulbs light up as well as the LED ones?

LED's are brighter. EX: I've tried the "xenon blue" bulb's for the flashers and tried the 48 LED Bulbs and the LED's are MUCH more powerful

[///Sniper535]

These are the only resistors i found with those specs. Will this work?

http://photos-f.ak.fbcdn.net/hphotos-ak-snc1/hs267.snc1/9424_522724665518_209700100_31283845_2857234_n.jpg

All the other standard resistors dont go higher than 1 watt.

http://photos-g.ak.fbcdn.net/hphotos-ak-snc1/hs267.snc1/9424_522724670508_209700100_31283846_7096993_n.jpg

[Qube]

Here's where I used to get them until I realized my local electronics hut has them cheap...

http://autolumination.com/equalizers.htm

[ss2115]

If I may, I've been down this road before of substituting LEDs for filament globes on several vehicle including C-class Mercs, Volvo's and the BMW.

The attraction of an LED being virtually maintenance free is certainly attractive, but in the end is a lot of mucking around if you have a vehicle that senses current draw etc to give globe out warnings.

Firstly, there's the fact that a globe has a considerably lower resistance once hot/lit, so the normal ohmage calculations don't actually work in regards to substituting for a globe.
As well, the globe draws different current at different voltages - ie: engine just started = low voltage (11.5?), alternator fully charging = high voltage (14.2?) and fully charged but lights on = somewhere in-between (13.6?).

Then if the resistor is in series, you’re limiting the current to the LED and so it’s not bright enough.
Resistor in parallel to "fool" the current sensor is correct as the LED will receive full voltage and light to the designed luminescence output.

However, the resistor in parallel with it is now drawing as much current as a globe in any case and so there is no saving at all in the electrical load in the vehicle which is one of the aims of a LED globe substitute.
And then, as stated by someone else here, the resistor has to sink a lot of current and its going to get really hot. So it’s going to be a wire wound in a ceramic case - quite a large item to find a place for and it’s still going to get hot and must be suitably mounted to prevent fire or smouldering smell.

So looking at all that, it is well worth changing to LED globes in cars that don't have globe out warnings, and boats and caravans, but its not worthwhile when trying to trick a vehicle with a globe out warning system.

Just my two cents worth.

[///Sniper535]

that's what I've been thinking, but will more LEDs in parallel do the trick?

[ss2115]

that's what I've been thinking, but will more LEDs in parallel do the trick?

No.
Because of the small current that LED's draw, you'd need a lot of them along with an appropriatly large wattage resistor to get to the point of simulating a filament globe. (the more current you draw, the larger the resistors wattage needs to become and then your back to the original problem of a huge resistor physical size that gets hot).
And in series won't work either because of the large (relative to LED's) voltage fluctuations in a vehicles electrical system, its very difficult to get it right. You have to allow for the highest voltage encountered and have a small safety margin, which then means that at the lower voltages encountered they are very dim or don't light at all (because LED's have a lower voltage threshhold where they won't light).

Thats why a commercial LED replacement globe has an inline resistor - to limit the current so that they can operate at varying voltages but limit the current they draw. This way they can stay at a similar brilliance through most of the voltage range they encounter, although are still prone to dimming or extinguishing at low voltages.
However, the current limiting resistor will not be enough to fool the Globe Out system because its so small as it only needs to cope with the minute current draw of the LED and is not trying to simulate the current draw of a filiment globe.

Another point is that an LED has very small resistance in its "forward" direction anyway. They are after all a diode - flow in one direction and block in the reverse direction. Light Emitting Diode.
So running many LED's in series won't be enough resitance for a Globe Out system anyway.

A possible solution is to pick a lower operating voltage for LED lights - eg: 9 or 12 volts, and install a 7809/12 voltage regulator in line with each globe location. The VR will handle 1 Amp and in most cases won't need a heat sink.
But then I don't know if this solution will solve the problem of current sensing relays or similar methods of Globe Out detection - I don't know what resistance is "seen" on the input side of one of these regulators.
Maybe? Someone clever'er than I might be able to answer this. Shogun?