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LED bulb for front fog lights

stevemc
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Re: LED bulb for front fog lights

Postby stevemc » Wed Apr 01, 2015 4:14 pm

You can get led bulbs with them all facing forward they sit in the original style bulb design

I posted the link to the site on a earlier post they have 9 Led all facing forwards none at the sides
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Equinoxstudios
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Re: LED bulb for front fog lights

Postby Equinoxstudios » Wed Apr 01, 2015 5:49 pm

I saw that link and it doesn't take you anywhere to find H3 LED foglight bulbs. What's the link to the page showing the bulbs you're talking about?
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Equinoxstudios
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Re: LED bulb for front fog lights

Postby Equinoxstudios » Wed Apr 01, 2015 6:26 pm

So here's my modified H3 50W 10xLED unit. I dismantled the LED boards from the original you see in my earlier posting. I shortened the body as much as I could (there is a driver circuit board inside the remaining tubular body section) and assembled the circuit boards so they all face front. This is now as close to ideal as possible. Bloody bright but still not as bright as a quartz halogen :|

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BAD NEWS - the Bulb Failure Monitor module flags it up as a blown bulb. So if you want to use even a 50W LED replacement you'll still need a big fat hot resistor across the two wires to convince it that a bulb is there. And that resistor WILL get very hot - it easily would melt its way through the plastic spoiler if it was left lying around so it will need mounting on heatsinks at the very least or bolted to a bit of chassis to get the heat away. And you need one for each foglight.
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baldilocks
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Re: LED bulb for front fog lights

Postby baldilocks » Thu Apr 02, 2015 2:40 am

Thanks Ivor, interesting approach. I must look at the reflector design as all light going forward may not be its optimum, as the original bulb is a point source effectively with much light out the sides coming off the rear reflctor (the bit that usually melts :D ) .
I can see this being a trade off between removing the heat of the halogen bulb that melts the fitting and reflector compared to actual lumens from the bulb/LED, taken in the context of how well or not they perfrom even with the H3 and all being good. Would be inclined to sacrifice some light to prevent inevitable melting. And lok at other H3 LED options or even other LEDs that could be made to fit, fog lights dont neccesarily need bright light, that sjust reflects from the fog its the diffusion to spread it over short range for low speed driving tahts actually the aim, fill in the gap out to the dipped beam.

As for BFM its an irritant needing the resistor as well but as you say mounted on chassis as a heat sink not a major. (Just another small part of the challenge.)
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Re: LED bulb for front fog lights

Postby abercanadian » Thu Apr 02, 2015 6:03 am

Equinoxstudios wrote:So here's my modified H3 50W 10xLED unit. I dismantled the LED boards from the original you see in my earlier posting. I shortened the body as much as I could (there is a driver circuit board inside the remaining tubular body section) and assembled the circuit boards so they all face front. This is now as close to ideal as possible. Bloody bright but still not as bright as a quartz halogen :|

BAD NEWS - the Bulb Failure Monitor module flags it up as a blown bulb. So if you want to use even a 50W LED replacement you'll still need a big fat hot resistor across the two wires to convince it that a bulb is there. And that resistor WILL get very hot - it easily would melt its way through the plastic spoiler if it was left lying around so it will need mounting on heatsinks at the very least or bolted to a bit of chassis to get the heat away. And you need one for each foglight.


Good effort there Ivor, can't fault you for trying! :)

Funny story - when I got the car the LH fog was melted back to a burned harness (I think the RH was still ok) but anyway in that condition I didn't get the bulb fail warning, :?: so I assumed the BFM didn't reflect the condition of the fogs.

Anyway, after much looking and time passing managed to get a couple of (fairly) good fogs which had failed in other ways, cracked lens on one etc - so I was able to cobble together a working pair (the reflectors can be swapped from left to right and vise versa).

After installing the new "good" pair and replacing the burnt LH harness I noticed the RH bulb had blown and to my surprise the "bulb out" light on the dash appeared - wonder why it didn't when the whole shebang had melted? :?

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Re: LED bulb for front fog lights

Postby Equinoxstudios » Thu Apr 02, 2015 11:18 am

Of course Baldilocks, the purpose of the curved reflector for a standard quartz halogen bulb is to convert the light radially emitted from the filament into parallel rays travelling out the front of the foglight unit. That is why a load of forward facing LEDs mimic the effect so well.

I'd like to play with some high power Cree LEDs to see what can be achieved...
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baldilocks
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Re: LED bulb for front fog lights

Postby baldilocks » Thu Jan 28, 2016 4:29 am

Week off work this week for wifes 50th but got opportunity to progress this slightly. Got to our local electronics stockist to see what 560 ohm resistors available, a 1W and a 5W. Liked idea of 5W as wire wound in ceramic so built in heat sink. Could not get 21W as recommended.

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Although waiting for new light fittings from UK I had James Jacked up to clean under engine, got a slight oil leak, so while there checked out what did and did not work. Interestingly just fitting the LEDs and bulb warning light went out, but went on soon as turned lights on, went off when lights turned off. So tried just the 5w 560 ohm resistor and got same result. So for now left the resistors there just to get rid of warning light. Tomorrow will pop back to shop and get 1K resistors, have seen other comments online, not here, that talk of using 1K resistor succesfully. See how that goes. As the resistors are 50p each its not off putting trialling!
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Equinoxstudios
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Re: LED bulb for front fog lights

Postby Equinoxstudios » Thu Jan 28, 2016 5:38 pm

Always be aware that the power rating of the resistor you are going to use is adequate.

With a typical 13.8V supply going to the fogs with the engine running, power dissipated in any resistor pretending to be a foglamp will be Vsquared divided by R which equals 190.44 divided by the resistor value. A 560ohm resistor will dissipate 340mW (less than half a watt) so the power rating of the resistors in your picture is more than adequate. However, 560ohm is nowhere near low enough for the job.

Trouble is that the bulb failure module is sensing the actual current drawn by each bulb it is monitoring. A real foglamp bulb is rated at 50W and consumes 50W of power (about 3.6A) but these LED bulb clusters that call themselves 50W DO NOT consume 50W - they consume perhaps only 14W (only about 1A) from the car electrical system.

In order to fool the BFM into thinking a real bulb is there you need to connect an additional resistor in parallel with the LED bulb. The additional current (another 2.6A) needed to fool the BFM therefore needs to flow through the resistor. A quick calculation (R=V/I) gives you a value of 6ohm with a power rating requirement (IxV) of over 30W.

So the experiment to try is to see what the highest value resistor is needed in order to fool the BFM. In this way you will end up with a resistor that runs the coolest it possibly can but do expect its resistance to be less than 20ohm and it will probably need to be 10W to 20W in power rating.

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norse_troll
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Re: LED bulb for front fog lights

Postby norse_troll » Fri Aug 04, 2017 9:56 am

Anyone who has successfully accomplished a transfer to led on front fog lamps?

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Re: LED bulb for front fog lights

Postby Quaduplex » Sun Jan 07, 2018 9:54 pm

What about H3 HID kits?

Same issue with current sensing?
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