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

[PILOON]

EMI and RFI!

Had an avionics shop and a client reports his ADF (Auto Direction Finder) is unserviceable.
Need it tomorrow!
My tech pulls the ADF and bench checks it as well as fine tune etc, re install and do an on board practical function test,
All is fine!
Naturally 2 weeks (was in a rush?) later he complains that we did lousy work blah blah etc. refuses to pay.

Well his problem was actually his alternator that had a blown diode and emitted RFI.
Aircraft magnetos were also noise generators as well as bad spark plugs.

(ADF operated below the AM frequency band)

 

[W8BYA]

EMI and RFI!

Had an avionics shop and a client reports his ADF (Auto Direction Finder) is unserviceable.
Need it tomorrow!
My tech pulls the ADF and bench checks it as well as fine tune etc, re install and do an on board practical function test,
All is fine!
Naturally 2 weeks (was in a rush?) later he complains that we did lousy work blah blah etc. refuses to pay.

Well his problem was actually his alternator that had a blown diode and emitted RFI.
Aircraft magnetos were also noise generators as well as bad spark plugs.

(ADF operated below the AM frequency band)

Yikes ! Yeah it can be really hard to explain to people not familiar with RFI/EMI issues just how complicated things can get. I digress here but along your lines I remember one of my first jobs (while waiting for my tickets to arrive) was to help solve a severe RFI issue on the BlackHawk helicopters. You might recall MANY years ago there were some very unfortunate incidents with that aircraft going down as a direct result of some susceptibility issues.

 

[k0ua]

RFI issues from most of our electronic devices is a problem that is getting worse by the day. It is a constant fight to keep bringing RF emitting devices into your house and keep re-engineering them by applying Ferrite chokes and bypass capacitors. Every device I bring into the house undergoes at least a quick look around the various frequencies I use to see how "bad" they are. If they fail the test, back to the store they go or into the trash.

It is not that the curse of the switch mode power supply cannot be made clean or nearly clean RF wise, because they can. It is a matter of spending a few cents or a few dollars at most for each device to make the clean that the manufacture wants to put that few cents extra into their pocket and multiplied by millions of units equals a lot of dollars.

As for those lights, the first thing I would try to do is place a .1 microfarad across the power line, and wrap some of the power line several turns thru a Mix 31 ferrite toroid. Say a 240-31 like these: The 240 part is the size of the toroid, and the 31 is the Mix number.

Ferrite Products for RF Chokes, Baluns, and RFI Mitigation

Or maybe even Mix 77 if the lower frequencies (like AM broadcast band) are the frequencies of most concern.


By the way, when you buy ferrite, if you don't know the Mix number (like 31, 43,77 etc) you don't have anything useful. When you buy ferrites from China or Amazon without the Mix number being stated, they are useless or nearly so. You have no idea what they are, what they will do for you or even if they are actually ferrite at all. I learned all of this the hard way.

 

[W8BYA]

Looking forward to the filter you make to remedy the problem.. thanks for sharing details.

This is also why many garage door openers have warnings not to use LED bulbs.. at least one member has had shop lights make his garage opener remote not work (or limit the distance severely).

I definitely will pass along what I find that worked and did not work in this case. Just need to remember that even with the same lights if they are installed on a different tractor with different harnesses and busses the fixes can vary.

Also that is a real good point about the LED light with garage door openers ! You would think they can add 1+ 1 together and see they are making junk products when not properly designed.

 

[Industrial Toys]

I have been hoarding ferrit cores out of scrapped equipment. I always wondered about the application implications.

 

[W8BYA]

Howdy James. That is one nice thing about having several VNA's around the shop....I sometimes will purposely buy ferrites that are unknown when I can get them for a steal then characterize them myself, mark them and put them in the appropriate plastic drawer for later consumption.

You and I think alike as far as what things to try first. I had just made up a parallel combo of a 1 uF, 0.1 uF and a 0.01 uF caps and was ready to try it out when I rubbed my eye and managed to get some sawdust etc into my eye. I was using the chainsaw an hour earlier and must have had some small shavings still in my hair or hat etc. Anyway saline flushes did not help and I was in real pain so before I did more damage to my Cornea off to the ER we went. Just got home and the doc found 2 small slivers pinned into my lid.

Anyway, we will start with the caps for giggles but I am not going to hold my breath. If I am real lucky and it is a common-mode issue then the ferrite bead with multiple turns may help. I suspect I will end up needing a more robust LPF design. Should be interesting & fun to see what it takes.....stay tuned. 73

 

[W8BYA]

I have been hoarding ferrit cores out of scrapped equipment. I always wondered about the application implications.

Given the price of ferrite beads and cores I, like you, snatch them up whenever I can. But the gotcha, as James noted is if you do not know their RF characteristics are your results can vary from 0 to 100.

I am lucky enough to have the test equipment to evaluate different cores then stock pile them into the correct groups. One of our fellow ham operators has generated several good documents that provides some really great information regarding different beads and where and when to use them. If you get a chance I recommend downloading and reading these documents:

http://www.w4ava.org/articles/k9yc-rfi.pdf

https://www.nccc.cc/pdf/Sep-K9YC-RFI2013.pdf

http://k9yc.com/2018Cookbook.pdf

 

[Industrial Toys]

Where do the LEDs radiate noise? In the LED array themselves, in the driver, or in the supply lines. Or all of the above. I have known for a long time how much RF, Walk/Don't Walk signs emmit and those things probably are anything but cheap. For shame!

My Beef is trying to reduce the emmisions of the computer in my E-Gator, basically a DC 48 volt golf cart. Even opens up the squelch on my DPLed VHF Motorola Radios at certain speeds. Thought of putting the cores on all lines in and out of the computer, but know nothing about doing this.

 

[radios1]

RFI issues from most of our electronic devices is a problem that is getting worse by the day. It is a constant fight to keep bringing RF emitting devices into your house and keep re-engineering them by applying Ferrite chokes and bypass capacitors. Every device I bring into the house undergoes at least a quick look around the various frequencies I use to see how "bad" they are. If they fail the test, back to the store they go or into the trash.

It is not that the curse of the switch mode power supply cannot be made clean or nearly clean RF wise, because they can. It is a matter of spending a few cents or a few dollars at most for each device to make the clean that the manufacture wants to put that few cents extra into their pocket and multiplied by millions of units equals a lot of dollars.

As for those lights, the first thing I would try to do is place a .1 microfarad across the power line, and wrap some of the power line several turns thru a Mix 31 ferrite toroid. Say a 240-31 like these: The 240 part is the size of the toroid, and the 31 is the Mix number.

Ferrite Products for RF Chokes, Baluns, and RFI Mitigation

Or maybe even Mix 77 if the lower frequencies (like AM broadcast band) are the frequencies of most concern.


By the way, when you buy ferrite, if you don't know the Mix number (like 31, 43,77 etc) you don't have anything useful. When you buy ferrites from China or Amazon without the Mix number being stated, they are useless or nearly so. You have no idea what they are, what they will do for you or even if they are actually ferrite at all. I learned all of this the hard way.

To determin the Al number for a magnetic material you can do this by calculating the inductance the "opposite way"
Make a coil of a certain number of turns, for instance 10 turns. check the inductance with a inductance meter. By using the equations for calculating the inductance you can turn the equation around to get a AL number. Check on the tables from the manufacturer/s to find a mix that correspond to the calculated AL number.

Another option is to use an antenna analyzer to find the AL number. Make a series resonance consisting of the inductor a good quality and known capacitor and a 50 ohm resistor. The resistor will give a very sharp dip in the SWR close to 1:1. Make a note of the frequency and use the equation for LC resonance to calculate the inductance. Then use the equation for inductance with AL number to calculate the AL number and check the table form the manufacturers.
This last method can also be used with a transceiver and low power and a homebrew uncalibrated absorption wattmeter. The only issue here is that you have to be within one of the ham bands or have the whole series resonance in a Faraday cage.

 

[W8BYA]

Where do the LEDs radiate noise? In the LED array themselves, in the driver, or in the supply lines. Or all of the above. I have known for a long time how much RF, Walk/Don't Walk signs emmit and those things probably are anything but cheap. For shame!

My Beef is trying to reduce the emmisions of the computer in my E-Gator, basically a DC 48 volt golf cart. Even opens up the squelch on my DPL Motorola Radios at certain speeds.

The issue is not the LED themselves but mostly the power supplies (or drivers) which power them. Decades ago most power supplies used linear topologies for generating the voltage references and for regulating them. They were RF quiet but not very efficient and tended to generate a lot of excess heat. Think of the heat generated by an old fashion 100W incandescent bulb vs a small LED lamp, both putting out the same amount of Lumens.

When switch mode power supplies were developed efficiencies sky-rocketed compared to linear based supplies ! Most SMPS use very high frequency oscillators, and being digital, they can have wicked fast rise and fall times on their waveforms. The faster the digital signal switches it's state the stronger & more broadband the noise it generates will be. This LED of mine had very fast rise & fall times which is why it blanketed everything from the AM band up past 200 MHz.

In addition the higher the current being provided by the SMPS the worse the situation will be. And, the longer the wires and harnesses the worse things will be. Some RFI will be generated within the LED enclosure and radiate directly but the vast majority of RFI will be conducted directly onto the power lines. But note that the RFI can then radiate directly off of those wires. The solution is to place inside the LED enclosure a power line filter. That way any RFI generated by the supply will not propagate throughout an entire system by contaminating every line using that power line bus.