Car Headlights, PWM

Home / the12volt's Install Bay / Lights, Neon, LEDs, HIDs / Car Headlights, PWM (

Topic Closed)

Welcome Guest :)

Members

Next Page > < Prev Topic Next Topic >

jasonlipka

Member - Posts: 49

Joined: March 18, 2008

Posted: July 06, 2012 at 11:57 AM / IP Logged

Hey guys, need some expertise here. I have a vehicle that has fancy new headlights, called "SmartBeam". Basically, it's an automatic high beam system. It worked really, really great before I started modding my vehicle. I installed HID's (high intensity discharge) lights. Each light is powered off its own fused +12V bosch relay.

Here's where the trouble began. Come to find out, the Smartbeam system doesn't just turn the high beams on and off. When it senses a car far off in the distance, it first begins dimming the high beams with PWM. When it dims them down to a nominal (and unknown) level, it shuts them off entirely. The problem is the PWM section. Obviously, my relays don't like this PWM at all. They are erratic on when they finally shut off and they make a terrible buzzing noise during the entire PWM cycle as they open and close a billion times a second.

I'd like to get rid of the PWM signal. There isn't a discrete wire in the car that I can pull off of thanks to the new CANBUS wiring system. I even tried the high beam indicator in the dash but it is a module. I have tried SSR's and they don't work. So I need some help. How do I do this?

I thought maybe a transistor as its saturation voltage is much lower than the pull in or hold in voltage of the relay coil. Would that work? I don't know how a transistor would respond to having a PWM signal applied to its base.

The other option is to filter it out with an R-C network right? Any ideas there?

Now for the bad news. I don't know the duty cycle, decay rate, or frequency of the PWM signal. I don't have an oscilloscope either. I have a DMM and am quite handy with it.

i am an idiot

Platinum - Posts: 13,672

This member consistently provides reliable information

Joined: September 21, 2006

Location: Louisiana, United States

Posted: July 06, 2012 at 4:21 PM / IP Logged

Parallel a 4700 microfarad 35 volt capacitor across the coil of the relay. If that does not totally take care of the problem, place a 6 amp diode in series with the wire feeding the coil of the relay.

faja

Member - Posts: 9

Joined: December 12, 2009

Location: Ontario, Canada

Posted: July 15, 2012 at 11:27 AM / IP Logged

check your owner's manual or with the dealer, there should be a way to simply disable the "smartbeam" option.

jasonlipka

Member - Posts: 49

Joined: March 18, 2008

Posted: December 12, 2012 at 9:17 AM / IP Logged

i am an idiot wrote:

I will give that a try. Any chance I will need to play with capacitance value? I only ask because it would save me money to just buy a couple different capacitor values using your guidance now than to keep buying them through trial and error.

Also, for my edification, what purpose does the diode serve? Not doubting you, I am just really curious how the diode affects the circuit.

Thanks for your input.

faja wrote:

check your owner's manual or with the dealer, there should be a way to simply disable the "smartbeam" option.

I know how to disable them, they are currently disabled. What I am saying is that the system functioned perfectly in automatic mode before I swapped to HID's. The HID ballasts are powered through relays. The relays don't like the PWM. It can be avoided by just disabling the smartbeams, but they function so well in automatic that I'd like to try getting them to function with relays in the circuit.

oldspark

Gold - Posts: 4,913

Joined: November 03, 2008

Location: Australia

Posted: December 12, 2012 at 4:25 PM / IP Logged

Remove the relays. Relays should not be PWM'd; only the lights. And since the Smartbeam is already supplying the power for the HIDs, the relays are unnecessary (unless BEFORE the Smartbeam).

The PWM should also be after the HID ballast depending on the ballast (some don't like the on-off PWM cycling) but it would have to be a grounding type (in case it can't handle the higher HID voltages).

i am an idiot

Platinum - Posts: 13,672

Joined: September 21, 2006

Location: Louisiana, United States

Posted: December 12, 2012 at 5:08 PM / IP Logged

I see no reason that the 4700 will not do what you are trying to do. But you can order a 1000, and a 2200 while you order. Try the 1000 by itself, if it does not do what you need, parallel the 2200 also. That will be 3200 total. If that still does not work then try the 4700. I am fairly confident that the 4700 along with the 6 amp diode will do the trick.

oldspark

Gold - Posts: 4,913

Joined: November 03, 2008

Location: Australia

Posted: December 12, 2012 at 7:50 PM / IP Logged

In that case I'd be tempted to remove or bypass the Smartbeam system altogether since its PWM dimming will be defeated - only its automated switch-down to low beam (below 27kph etc) would remain.

Other sources also reckon the PWM causes havoc with HID ballast. (Though as I say, that depends on ballast design, though shorter life may ensue even if they do work.)

jasonlipka

Member - Posts: 49

Joined: March 18, 2008

Posted: December 13, 2012 at 1:17 PM / IP Logged

oldspark wrote:

In that case I'd be tempted to remove or bypass the Smartbeam system altogether since its PWM dimming will be defeated - only its automated switch-down to low beam (below 27kph etc) would remain.

Other sources also reckon the PWM causes havoc with HID ballast. (Though as I say, that depends on ballast design, though shorter life may ensue even if they do work.)

I tried hooking the ballasts directly to the high beams and the lights still flcker. The PWM must be removed from the circuit.

jasonlipka

Member - Posts: 49

Joined: March 18, 2008

Posted: December 13, 2012 at 1:19 PM / IP Logged

i am an idiot wrote:

Okay, I have them on order. Not gonna be here until next week.

I ask again, what purpose does the diode serve?

i am an idiot

Platinum - Posts: 13,672

Joined: September 21, 2006

Location: Louisiana, United States

Posted: December 13, 2012 at 9:36 PM / IP Logged

For the times that the PWM is at 0, the diode keeps the cap from trying to keep that voltage up. It will use all of it's capacitance to keep the relay energized.

Next Page >

Printable version

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot delete your posts in this forum
You cannot edit your posts in this forum
You cannot create polls in this forum
You cannot vote in polls in this forum

Search the12volt.com

Follow the12volt.com

Disclaimer: *All information on this site ( the12volt.com ) is provided "as is" without any warranty of any kind, either expressed or implied, including but not limited to fitness for a particular use. Any user assumes the entire risk as to the accuracy and use of this information. Please verify all wire colors and diagrams before applying any information.