Click to go to Forum Home Click to go to maXbimmer Home

Go Back   maXbimmer Forums > maXimum Tech > 3 Series > E46 (1998 - 2005)
User Name
Password


Welcome to Maxbimmer.com!

You are currently viewing our boards as a guest which gives you limited access to view most discussions and access our other features. By joining our free community you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is fast, simple and absolutely free so please, join our community today!

Reply
 
Thread Tools Rate Thread Display Modes
Old 08-01-2009, 02:00 PM   #1
Rockblock
2nd Gear Member
 
Rockblock's Avatar
 
Join Date: Jul 2007
Location: GTA
Posts: 95
What's the best place to mount Load Resitors for LED bulbs?

I'm planning to get a set of LED bulbs to replace my P21W turn signal bulbs (F+R) + 4 resistors to put in parallel with each LED bulb to lower blinking frequency. I've heard that the resistors (6 ohms/50W) heat up pretty bad, so I'd like to know where have you guys mounted them (both front + back) and what your overall experience is? Any pics would also be appreciated. These are the resistors I've been told I should get:
Attached Images
File Type: jpg Load resistors.jpg (38.2 KB, 106 views)
__________________

_________________________________________________
The more expensive the car, the cheaper the spare parts should be !
Rockblock is offline   Reply With Quote
Old 08-01-2009, 08:22 PM   #2
Porter86
shiftin gears
 
Porter86's Avatar
 
Join Date: Mar 2009
Location: Oakville, Ontario
Posts: 271
Send a message via MSN to Porter86
your fronts aren't PY21W?? mine are,lol.
Porter86 is offline   Reply With Quote
Old 08-01-2009, 10:53 PM   #3
Rockblock
2nd Gear Member
 
Rockblock's Avatar
 
Join Date: Jul 2007
Location: GTA
Posts: 95
Quote:
Originally Posted by Porter86 View Post
your fronts aren't PY21W?? mine are,lol.
on one it says "Philips 12V P21W 1057" on the other "Philips 12V 7056 P21W"...go figure...anyway, I plan to replace them with white LEDs, but I need to put resistors and am looking for the best metallic spot because they generate a lot of heat
__________________

_________________________________________________
The more expensive the car, the cheaper the spare parts should be !

Last edited by Rockblock; 08-01-2009 at 10:56 PM.
Rockblock is offline   Reply With Quote
Old 08-02-2009, 02:37 AM   #4
Porter86
shiftin gears
 
Porter86's Avatar
 
Join Date: Mar 2009
Location: Oakville, Ontario
Posts: 271
Send a message via MSN to Porter86
nice!! let me know what you come up with, cause i need to get rid of the orange lights as well. i hope someone can give you a hint better than me asking questions lol.
Porter86 is offline   Reply With Quote
Old 08-02-2009, 03:29 AM   #5
Steve@ASPTuning
2nd Gear Member
 
Join Date: Jun 2008
Location: Calgary, AB
Posts: 288
You'll have to make a customer aluminum plate to mount those resistors to. Then you have to find somewhere in the fender area to mount the aluminum plate to so that the heat can be transferred from your resistor to the plate, and then to the fender. But just mount those resistors away from ANY thing that will melt or possibly catch on fire due to the heat.

I personally wouldn't take a chance and install these resistors as its pretty hard on your LCM, and I've heard a few cases where some people's LCM burn out, and costs them $600.00 for a new LCM then to get it coded to your car is even more $$$ on top from the stealership.

But goodluck, and one word of advice, get resistors that have a higher ohm such as 100ohms at 25 watts. The higher the ohms I find the less heat it produces.

Hope that helps.

Steve
ASPTuning
Steve@ASPTuning is offline   Reply With Quote
Old 08-02-2009, 11:33 AM   #6
Rockblock
2nd Gear Member
 
Rockblock's Avatar
 
Join Date: Jul 2007
Location: GTA
Posts: 95
Quote:
Originally Posted by Steve@ASPTuning View Post
You'll have to make a customer aluminum plate to mount those resistors to. Then you have to find somewhere in the fender area to mount the aluminum plate to so that the heat can be transferred from your resistor to the plate, and then to the fender. But just mount those resistors away from ANY thing that will melt or possibly catch on fire due to the heat.

I personally wouldn't take a chance and install these resistors as its pretty hard on your LCM, and I've heard a few cases where some people's LCM burn out, and costs them $600.00 for a new LCM then to get it coded to your car is even more $$$ on top from the stealership.

But goodluck, and one word of advice, get resistors that have a higher ohm such as 100ohms at 25 watts. The higher the ohms I find the less heat it produces.

Hope that helps.

Steve
ASPTuning
hmmm...now you got me thinking...with respect to the resistors, I also thought that a higher ohm value would solve the heating problem, but I've seen everyone using the 6 ohms (I haven't seen any 100 ohms/25W)...

But aren't the LED bulbs + resistors supposed to draw less amps than the stock 21W bulbs?...a quick calculation reveals that when signaling, the stock bulbs draw a max 21W/12V = 1.75A...while at night, they'd draw a constant ~600-700 mA (since they operate @ aprox. 30-40% nominal power).

So, wouldn't I have to look at ensuring that the total Amp draw Amp1 (LED) + Amp2 (Resistor) < 1.75A? If I go with the 6 ohms/50W, Amp2 > 2A, so no good...if I use a 100 ohm/25W resistor, then Amp2 = 125mA, which is OK...so, basically, Amp1 (LED) would have to draw a max of 1.625A, which I think they don't... so wouldn't the LEDs actually put less stress on the LCM?

Now, I also run CCFL Angel Eyes that pull a total of 1.4 Amps staright from the LCM (no relay, straight from the aux wire)...so I need to do some more thinking on this...

Problem is, with the AE @ 7000K, the signals (which I run through clears) look really bad, especially when driving @ night, when they're on all the time and produce 30% power and look very pale...

Anyway, thx for your thoughts Steve.
__________________

_________________________________________________
The more expensive the car, the cheaper the spare parts should be !
Rockblock is offline   Reply With Quote
Old 08-03-2009, 12:17 AM   #7
Rockblock
2nd Gear Member
 
Rockblock's Avatar
 
Join Date: Jul 2007
Location: GTA
Posts: 95
Quote:
Originally Posted by Rockblock View Post
a quick calculation reveals that when signaling, the stock bulbs draw a max 21W/12V = 1.75A...while at night, they'd draw a constant ~600-700 mA (since they operate @ aprox. 30-40% nominal power).

So, wouldn't I have to look at ensuring that the total Amp draw Amp1 (LED) + Amp2 (Resistor) < 1.75A? If I go with the 6 ohms/50W, Amp2 > 2A, so no good...if I use a 100 ohm/25W resistor, then Amp2 = 125mA, which is OK...so, basically, Amp1 (LED) would have to draw a max of 1.625A, which I think they don't... so wouldn't the LEDs actually put less stress on the LCM?
I used Power law equation ( P = V * I ) as well as Kirchhoff's Current Law [ I = I1(Amp1) + I2 (Amp2) ] to calculate values, as per attached diagram.

Can anyone confirm/refute ? Thx
Attached Images
File Type: jpg LED load resitor wiring diagram 2.jpg (40.4 KB, 92 views)
__________________

_________________________________________________
The more expensive the car, the cheaper the spare parts should be !

Last edited by Rockblock; 08-03-2009 at 12:20 AM.
Rockblock is offline   Reply With Quote
Old 08-03-2009, 01:28 AM   #8
Porter86
shiftin gears
 
Porter86's Avatar
 
Join Date: Mar 2009
Location: Oakville, Ontario
Posts: 271
Send a message via MSN to Porter86
i don't know much about resistors, never got into them to much with my electrical night class, n i took gas and oil burner tech 1 and 2. but the way you have that set up is in parallel, because how it works is that your power goes out on one and comes back on the other. like i said, i never touched bass on them to much, but what makes sense to me, is that by doing that your going to just diver it in parallel and its never going to effect the led light.

cause the meaning behind parallel is that everything connected in that line gets the same amps, volts, what ever, now to run it in series, is a different, because it has to go in the resistor and than out the resistor which goes in the light and than back.

like i said, we never really got fully involved with them,

resistor.jpg

i guess someone correct me if im wrong as well,lol.
Porter86 is offline   Reply With Quote
Old 08-03-2009, 10:32 AM   #9
Rockblock
2nd Gear Member
 
Rockblock's Avatar
 
Join Date: Jul 2007
Location: GTA
Posts: 95
Quote:
Originally Posted by Porter86 View Post
cause the meaning behind parallel is that everything connected in that line gets the same amps, volts, what ever

i guess someone correct me if im wrong as well,lol.
When you run stuff in parallel, you maintain a constant Voltage, but your Current gets split (Kirchoff's current law) and your overall current (i) will be the sum of the current drawn from LED (I1) + current drawn from Resistor (I2) - see my diagram above

When you run stuff in series, your current is constant (I), but you'll have Voltage drops, so the Resistor will pick up a certain Voltage, thus your LEDs will be left with less than 12V to operate so this needs to be compensated...now putting a resistor in series that has a total ohm value = Bulb - LED may do the trick, provided the LED resistance < Bulb and are quite close in values...I don't have any LED bulbs to measure - and they all are different based on the design & # of LEDs (one with 12 LEDs will have a different value than one with 36)- but if anyone has the capability of measuring some LEDs, it would be interesting to see how much ohms they carry...also, in this case the challenge will be to find LEDs that can operate effectively at slightly less than 12V
__________________

_________________________________________________
The more expensive the car, the cheaper the spare parts should be !

Last edited by Rockblock; 08-03-2009 at 11:21 AM.
Rockblock is offline   Reply With Quote
Old 08-04-2009, 01:48 AM   #10
Steve@ASPTuning
2nd Gear Member
 
Join Date: Jun 2008
Location: Calgary, AB
Posts: 288
Rockblock, I'm not too familiar with the Kirchoff's law, but it looks correct. My only concern is that when you split up the resistance one going to positive and one going to negative y putting it into a series it looks more of a job of a capacitor... Could you not technically put a capacitor first? then a resistor? I'm sure you can add a capacitor to filter out electrical noise, and account for any spikes/drops in the electrical system.

As for putting less stress on the LCM because your LED's are drawing about 1.625A is right to say. But then again I've never ever tested a LCM out to its threshold to see what is the max amperage it can take before it burns out or what the pro-longed causes may be by adding in a resistor.

Theoretically speaking here:
Assuming most LED's operate at 2V when its working and 10mA current. The power supply being 12V. Now we have to figure out what the resistance value is for the resistor which is 12 - 2 = 10V (The voltages across components in series must add up to the power supply voltage.)

Using the formula R = V / I we have V (Voltage) and I (mA - Current of LED), converting 10mA to amp is 0.01.
It would be R = 10 / 0.01 = 1,000 ohms.

So technically you need a 1000ohm resistor? now thinking about its probably impossible to get a 1000ohm resistor. I know you can get 500ohm resistors but you'll need two of them to equal the power of 1000ohms.

Can this be right? and I would say... 100ohms would be sufficient but according my calculation you need a 1000ohm resistor. Please let me know if this is correct???

and yes LED's only run in a series of 12.

Thanks,
Steven

P.S. this has turned out to be quite the discussion!!! It's good for those wanting to upgrade to a 36 LED front turn signal but with caution and don't want to burn out their LCM like some...

Last edited by Steve@ASPTuning; 08-04-2009 at 01:54 AM.
Steve@ASPTuning is offline   Reply With Quote
Old 08-04-2009, 05:49 PM   #11
Rockblock
2nd Gear Member
 
Rockblock's Avatar
 
Join Date: Jul 2007
Location: GTA
Posts: 95
Well, here's what I'm thinking ....if I had a variable resistor (something like a rheostat with low ohms), I could connect it in paralell to the LED bulb and then increase the ohms value from 6 ohms -> up untill I get the "bulb out" warning. Then I'd know exactly what resistor to put.

...but unfortunately, I don't have a low ohms rheostat ... so I'm hoping we can find someone that has one and will be able to shed some light to this topic...
__________________

_________________________________________________
The more expensive the car, the cheaper the spare parts should be !

Last edited by Rockblock; 08-04-2009 at 05:51 PM.
Rockblock is offline   Reply With Quote
Old 08-05-2009, 12:57 AM   #12
Steve@ASPTuning
2nd Gear Member
 
Join Date: Jun 2008
Location: Calgary, AB
Posts: 288
That would work! Except your right... what supplier has a low ohms rheostat.... I'm sure there's one out there but its REALLY HARD to find it.
Steve@ASPTuning is offline   Reply With Quote
Old 08-05-2009, 12:40 PM   #13
Rockblock
2nd Gear Member
 
Rockblock's Avatar
 
Join Date: Jul 2007
Location: GTA
Posts: 95
Quote:
Originally Posted by Steve@ASPTuning View Post
That would work! Except your right... what supplier has a low ohms rheostat.... I'm sure there's one out there but its REALLY HARD to find it.
Maybe a student with access to a Lab can borrow one?
__________________

_________________________________________________
The more expensive the car, the cheaper the spare parts should be !
Rockblock is offline   Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


All times are GMT -4. The time now is 10:59 PM.


Powered by vBulletin® Version 3.8.1
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.