LED headlights/driving lights - radio noise suppression

[Bagger John - #3785]

Earlier this year I scored a set of OEM H-D LED spotlights at a price I simply couldn't pass up. Shortly thereafter I got hold of one of their OEM projector headlights, also for a price I couldn't refuse.

I'd had Josh's bracket on-hand for a while, and decided to give the installation a go on my Tourer. Mechanically, once things fell into place the headlight installation was straightforward - as was the spotlight install. Aiming was done empirically and once I had things dialed in I was very impressed with the results.

That is, until I turned the bike's radio on. FWIW, this is the Hondaline (Clarion) CB which is connected to a Kennedy FRSet4 integrator, allowing the dual-band ham rig I have on the bike to utilize the Hondaline mic audio for transmitting. In receive, the ham rig's audio is routed to the CB's Line In connection - allowing me to hear both and transmit on either.

All worked fine with the stock incandescent headlight and spots. The LED units put out so much RFI that the squelch had to be turned all the way up to mute the CB receiver. I'm guessing on the order of 200uV or more RF energy at 27MHz, though I didn't put the lights on my spectrum analyzer to verify.

I ended up diving back into basic electronics theory and turned to my old friend the Pi filter. It's an effective EMI suppressor. The headlight current draw was measured (~3A each for low and high beam) and a bunch of 100uH, 6A toroid chokes were obtained. These are 13mm in diameter and 8mm thick - small enough to mount inside the headlight casing with the other electronics.

The other components used are 100uF, 35WVDC electrolytic capacitors. One inductor and two capacitors are used on each "beam" connection; the feeds to the PWM controller board were unsoldered and the filters inserted there.

Schematically:



"VIn" is the supply side connection, "VOut" is the feed to the headlight's controller board and "Ground" (the common line at the bottom) is the PWM board's ground connection. The (+) terminals of the capacitors go to the inductor (In and Out side) while the (-) goes to Gnd. I chose to mount the components inside my light to positively suppress EMI at its source. This can be a dicey job, so familiarity with reworking or modifying such circuitry is a foregone conclusion.

The results...turn the CB on without the light connected. Unsquelch it and listen to the background noise. Plug the headlight in - the ambient level barely changes. Activating the High beam (which turns on all the LEDs in my particular light) generates a little more noise but signals which were at the noise level are still readable. Without putting a scope and analyzer on the setup, I'm betting the total noise increase with the filtering in place is less than 1uV - probably close to 0.2.

The same circuit was applied to the spotlight feeds, albeit externally - there's no way to open the cases. I was able to get their combined noise level down to roughly 30-40uV - equivalent to setting the radio's squelch to "10" before quieting is achieved. More work in this area to follow.

I'll post a pic of the modified PWM board if anyone's interested.

[-mike-]

GREAT post! Thanks!
I'd like to see more for sure.

-mike-

[Jims99]

Yes, please keep us informed. I have tried a few standard filters with no luck. LED headlights along with turn, running and brake. Seems only the headlights are giving me problems (fm radio) I use my phone for music most of the time. Thanks

[Bagger John - #3785]

Views of the individual components I used:



The toroids have P/N 13C5-4-4 on the bag. They were obtained from eBay along with the capacitors.

Pic of the modified PWM board:



This was done in so-called "dead bug" construction. All four capacitor grounds are tied together and that lead was soldered to the GND foil of the board (heavy black wire coming into the light). Red and blue are High and Low beams; these were unsoldered from the PCB and attached to the input sides of the filters. The filter outputs were soldered to the PCB tracks where the red and blue wires originally attached.

After verifying operation on the bench, I applied a couple shots of Automotive Goop adhesive for shock resistance. When cured, the assembly was put back in its housing and secured.

If I was designing this thing from scratch I'd have laid out another PCB and used it to hold the filter components in piggyback fashion. There's more than enough room in the light to do it right.

ETA:

I did not put a filter on the "halo" wiring, nor did I test for noise there. That portion of the circuit can be treated similarly if it generates excessive RF noise. I don't run mine - but those in EU countries who have DRL restrictions may want to be aware of potential gotchas.

[-mike-]

I'm still wondering if this would be a solution for a separate electronic box.

I have something like this:
https://i.ebayimg.com/images/g/ydYAAOSwGAhf34Xe/s-l400.jpg

So what do you think? Building these LC Filters and splicing them in?
On both sides of the box?

Another question: 100μF x2 parallel vs a single 200mF in the filter? Any thoughts behind that?
Or just what standard size you had lying around?

-mike-

[Bagger John - #3785]

I'm still wondering if this would be a solution for a separate electronic box.

I have something like this:
https://i.ebayimg.com/images/g/ydYAAOSwGAhf34Xe/s-l400.jpg

So what do you think? Building these LC Filters and splicing them in?
On both sides of the box?

Another question: 100μF x2 parallel vs a single 200mF in the filter? Any thoughts behind that?
Or just what standard size you had lying around?

-mike-

Mike,

I'd tried an inline suppressor for the spots. It's marginally effective (see post above) but if the light in question can't be opened that may be the only way to go.

I found mention of a couple of inline units on one of the HD forums and decided to order the one which most members had good success with. All the unit turned out to be is a capacitor from the low beam wire to ground. Might work for those lights which run the low beam all the time and switch just the "high" elements, but then again it might not. Good engineering practice in this case dictates that you filter EVERY lead going into the unit, as they become potential radiators.

There's also the question of space: There isn't a lot left inside my Tourer's headlight bucket. I had to make the mod internal to the light.

The parts I chose were selected as a starting point. If they weren't successful at knocking down the RFI by a good amount, each 100uF capacitor would also have a 0.1uF/100v and a 0.01uF/100v ceramic disc type placed across it - these are basically a short at radio frequencies.

[-mike-]

John, thanks for your input, i really appreciate it!
Unfortunately there's no way to get these filters into that cases. I thought to put two LC Filters (low/high beam) as close to the box as possible. Else Ibthink the wiring may act as an antenna for the RF noise, too.

I tried those ferrite RF chokes 2 at input, 2 at out and got somewhat less noise.
I have a Standard, so there's no radio bothering me, but I don't want the lights to interfere with the CDI or the Jersey flasher unit. Not experienced issues for a year, but I want to play it safe

True, there's not much space in the lamp bucket for ballast, LED lamp cooling fins, Jersey flasher and OEM wiring. Not sure if I could get decently built LC filters into it, too.

Maybe I should just sell the lamp and get a (electronically) better built one instead.

-mike-

[Bagger John - #3785]

Are you using a projector light (HD Daymaker or equivalent) or a replacement LED bulb, Mike?

[-mike-]

I know of LED inserts, have seen them often with a massive plus in light and light pattern improvement.
Too modern in appearance for my taste.

I try to keep the classic look, so a LED bulb not too white or blueish it is. Or would be nice.
Still a high output filament bulb makes the best appearance, but LED keeps the load low on switch and alternator and offers a tad more light, too.

[Jersey]

How do you like the FRSet4?  I've thought about combining the ham unit. Just recently got the OEM CB to add.  Had looked at the integrator awhile ago and never came to it.  Just curious what you think.

Thanks,
Jersey

[Bagger John - #3785]

How do you like the FRSet4?  I've thought about combining the ham unit. Just recently got the OEM CB to add.  Had looked at the integrator awhile ago and never came to it.  Just curious what you think.

Thanks,
Jersey

I have them on three of my bikes at the moment. My Tourer (mentioned above) has a dual-band ham rig hard-wired into it. The I/S installation has a set of pigtails brought out to the handlebar area for use in attaching a VX-6 or VX-7R, but I could swap the radio cables for use with a Motorola Spirit MURS rig, Midland or similar FRS/GMRS handheld, etc.

My '08 Concours 14 has a JMCB-2003 installed, with the FRSet4 and a dual-band ham rig all integrated. Jon of Kennedy built a special setup for me that enables selection of either the ham rig or a connected MURS/FRS-GMRS transceiver.
 
Note that an FRSet4 only works with an existing audio system - such as the J&M CB unit, the GL1500/1800 Wing's entertainment system, the Hondaline/Clarion CB offered as an accessory for the Standard/Tourer - or the I/S stereo. There's some custom work required to get the FRSet4 to integrate cleanly with a GL1500CF setup. Jon said it couldn't be done. I did it, wrote the procedure up and drew lots of nice documents to help the next guy out. He may have them; if not I'll be happy to provide the information.

If your bike doesn't have an audio system, I'd recommend the MotoChello MC200.

https://www.motochello.com/200-system/

I'm doing some custom integration work with one of those, an FTM-10R and an IC-703+ for my '12 C14. The device has an I/O port for a cell phone (no PTT function) and an I/O port for a transceiver of some sort (with PTT function). I figured a way to get two transceivers working with the unit and will write that up as soon as the setup is built, debugged and on the bike.

[Bagger John - #3785]

I know of LED inserts, have seen them often with a massive plus in light and light pattern improvement.
Too modern in appearance for my taste.

I try to keep the classic look, so a LED bulb not too white or blueish it is. Or would be nice.
Still a high output filament bulb makes the best appearance, but LED keeps the load low on switch and alternator and offers a tad more light, too.

Here's the gotcha in a nutshell with bulb replacements vs replacing the entire unit:

Noise filtering.

With a Daymaker or similar unit that's enclosed in an all-metal headlight housing, you can contain any EMI by choking it off at the power feed points. This is much harder to accomplish when you install a LED replacement bulb into the Valkyrie's stock reflector unit, as almost nothing in the reflector assembly is grounded. (It doesn't have to be when using an incandescent bulb).

LED lights are not constantly "on", much as light bulbs powered by AC aren't constantly "on" either. This has to do with the individual LED chip's power dissipation capabilities. It's easy to get a LED light's instantaneous output to be very bright without its average dissipation rating being exceeded. This is accomplished with a circuit called a pulse width modulator (PWM).

If you could look at the output of the PWM/input to the LED chips with a scope, you'd see something akin to this:



Most automotive LEDs use a PWM whose oscillator frequency is ~10KHz. Unfortunately, square waves (seen above) love to generate harmonics and will do so high into the HF region. They may be weak compared to the fundamental at those frequencies but are still high enough in amplitude to trash your radio reception.