Beware of possible issues when installing some LED lights on your tractor

[W8BYA]

It's great that you posted this also and all the work you're doing to solve it. Wow! This "There is over 1.6 V(p-p) RFI riding on top of the 13.8 VDC power line !"
is amazing and explains so many problems people (may) experience using LEDs.
Before retiring I was a troubleshooter, primarily consumer electronics.
The diode/cap idea was a simple isolation thought which would drop LED supply by about 0.65-0.7V (with it's smps wouldn't affect light output).
It would be more complexity but a separate battery such as an inexpensive (like Everstart 230 cca $22), LEDs powered by it, that battery then charged by isolation diode from tractor alternator.
Me...I'd be thinking of ditching LEDs in favor of halogen!

I'm a little intrigued by the diode/cap idea, would you be willing to e-mail me a sample schematic drawn on the back of a napkin of a simplified example of it's execution? My e-mail is w8bya at mchsi dot com. I would like to see that and possibly mess around with it purely because I'm a geek and miss doing engineering work so it would be fun some cold wintery night.

Also, I can understand wanting to ditch LED's all together but we need to remember that not everyone has issues with them because as noted earlier it takes two to tango.....you need a trouble maker but you also must have something susceptible to that trouble maker. If your equipment already has filtering or simply is not susceptible then heck keep using them. They are very bright and draw way less power. And they will outlast the tractor and any halogen bulbs <g>.

 

[Fuddy1952]

This is a simple draw app (my finger is shaky)...very simple. B+ is power source, cathode has electrolytic cap to ground, this is now source to lights.
Of course this would be close to LED, maybe one for each. With your o-scope probe here, value of cap for lowest p-p noise level. Who knows...1,000 ufd @ 25v, a low esr hi temp quality cap?

 

[W8BYA]

This is a simple draw app (my finger is shaky)...very simple. B+ is power source, cathode has electrolytic cap to ground, this is now source to lights.
Of course this would be close to LED, maybe one for each. With your o-scope probe here, value of cap for lowest p-p noise level. Who knows...1,000 ufd @ 25v, a low esr hi temp quality cap?View attachment 629111

Ok but remember it is not the LED's that are causing the issue. It is the power supply that is generating the B+ (BTW you just gave your age away <g>).

We are worried about what the power supply (that is generating the B+ in this case) is injecting back onto the raw DC supply lines ! There is a country mile of electronics between the LED's (load) and the DC supply voltage.

 

[k0ua]

I figured what ever noise suppression components the OEM had put in the little power supply had failed in an open condition. (like a capacitor) and that was why all of a sudden one day, it was trash city coming from the little supply. I probably should have kept it as a lab curiosity, but I was afraid it would get mixed in with all the other little "wall warts" I have laying around.

 

[Fuddy1952]

I haven't read through all the 70+ posts, but my understanding was you have an New Holland tractor that all was well. You replaced the factory halogen lights with LED lights. This created noise problems because the LED lights have their own smps which are adding that 1.6vp-p ("pulse, noise") onto DC.
Now instead of "clean" DC (except when running whatever little bit alternator pulses) you have this which affects radio, possibly computer, etc.
Isolation diode and filter cap hopefully would block this feedback from LED lights back onto tractor power line.
Am I correct?

 

[W8BYA]

I haven't read through all the 70+ posts, but my understanding was you have an New Holland tractor that all was well. You replaced the factory halogen lights with LED lights. This created noise problems because the LED lights have their own smps which are adding that 1.6vp-p ("pulse, noise") onto DC.
Now instead of "clean" DC (except when running whatever little bit alternator pulses) you have this which affects radio, possibly computer, etc.
Isolation diode and filter cap hopefully would block this feedback from LED lights back onto tractor power line.
Am I correct?

You have 99% of it correct. Imagine the 13.8 VDC from the tractor feeding a SMPS. The output from the SMPS feeds the individual LED lights. The SMPS and LED's are all inside a die-cast aluminum enclosure. The issue is the SMPS contaminates (inadvertently) the 13.8 VDC supply (INPUT) voltage from the tractor.

Filtering the DC voltage after the SMPS going to the LED's would not help matters. We need to filter between the SMPS and the tractors 13.8 VDC.

 

[Fuddy1952]

I understand and we're on the same page.
Ok...
"The SMPS and LED's are all inside a die-cast aluminum enclosure. The issue is the SMPS contaminates (inadvertently) the 13.8 VDC supply (INPUT) voltage from the tractor."

What I'm trying to say in that simple drawing is do not supply LEDs tractor power. Instead tractor power to anode of diode. Diode cathode to LED supply.
I'd use one diode+cap each light.
Instead of 13.8v going to each LED you would have 13.1v. Scope this point. Cap value for lowest noise.
Simple...hopefully this diode/filter cap prevents feedback from LED back to tractor "B+".

I used ECG125 diodes all the time. 1000 prv, 2.5A.

 

[W8BYA]

I understand and we're on the same page.
Ok...
"The SMPS and LED's are all inside a die-cast aluminum enclosure. The issue is the SMPS contaminates (inadvertently) the 13.8 VDC supply (INPUT) voltage from the tractor."

What I'm trying to say in that simple drawing is do not supply LEDs tractor power. Instead tractor power to anode of diode. Diode cathode to LED supply.
I'd use one diode+cap each light.
Instead of 13.8v going to each LED you would have 13.1v. Scope this point. Cap value for lowest noise.
Simple...hopefully this diode/filter cap prevents feedback from LED back to tractor "B+".

I used ECG125 diodes all the time. 1000 prv, 2.5A.

Ok I think I see the issue here. In your drawing you have it labeled as LED's. I think what you wanted to say was "LED Assembly" is that correct? You would like to see the diode and cap BEFORE the entire LED LIGHT ASSEMBLY....right?

 

[Fuddy1952]

Yes! Exactly right...now we're @100%!

 

[mcfarmall]

Ran into a similar issue when I replaced the incandescent lamps in my travel trailer lights with LED's. My weather radio was essentially useless. I figured it out by process of elimination because the radio worked fine during the day but was junk after dark when I had lights on. Happened to walk out of the trailer when the radio was on and the interference went away when I turned off the light!