pemiller

HELP!

I'm using a Castle Creations 25 amp ESC in an Alfa F-86. I've tried several different brands/models of receivers and with all I'm getting severe interference, e.g., servos jumping around, ESC pulsing the motor RPM up and down; the problem seems to be worse at certain RPMs. Even without the motor running, the servos jump around when the ESC arms, e.g., when it chirps. I tried a ferrite ring on the end of the ESC control wire, but it didn't help. I'm lost! [&:] Any ideas?!?

Thanks

/pem

skywca

***Warning*** Do not fly your Sabre until you resolve this problem. You will likely lose control of it in flight if you attempt to fly it.

I've been enjoying electric flight for about a year now, and hve lost several airplanes for the same reason. The twitching that occured when I flew brushed airplanes, became even worse when I started flying with brushless power on 2 cells, and even worse on 3 cells. Though magazine articles mention routing of wires neatly and using capacitors on brushed motors, no one does a good job of explaining how to avoid this problem.

First, on the ground with the aircraft secure, power-on the system and look for glitches at idle. Try moving your wiring to see if there is more interference, i.e. battery wires near speed control-receiver wire, battery near motor leads, speed control-receive wire near motor leads. You may see minor twitching of the servos when these wires are moved closer.

Second, repeat this test with incremental increases in power i.e. low, mid, high power. The problem likely worsens as power increases.

If this is happening to your Sabre, what you have found is severe interference as a result of the high current flow from battery to esc, and from esc to motor.

The remedy that I have found to work for me is simple, and costs pennies. I cut 1" strips of regular aluminum foil. Before installing the esc, I wrap each group of wires (esc-receiver, battery, motor) with the foil at a 45' angle along the length of wire. I then tape the foil in 2-3 spots. Install the esc, and fold lengths of excess wire taping it to hold. I ensure each wire group is as far from another as possible. Though I've used Heavy-duty for more protection, it isn't quite as flexible. Regular duty foil should work since it is being layered. I then range-check my radio to ensure that I have no more interference. I also switched to using dual-conversion receivers for added protection. Though this may not be neccessary if the foil wrap takes care of the problem.


Fly safe!

Woody 51

An interesting fix. Please post the results as many others will be interested in the outcome.

pemiller

Sky,

Just to ensure I understand: When you say "wire groups" that would mean, for example, all three wires from the ESC to the brushless motor in one wrapper? Is that correct?

I've been working this problem exactly as you suggest: I have the entire system, incuding the motor/turbine assembly, taped to the kitchen countertop while I run my tests. Moving the wires around and relocating the components does not solve the problem, it only changes the symptoms. I'll try your foil idea, aka RF cable shielding; I may also try to use the outer shield of some coaxial cable; short lengths of this wire braid can be easily removed, and then slipped over the wires in question. It would be smart to tape the ends of the shielding to ensure that "whiskers" do not make contact with anything. This idea (RF wire braid) may be too heavy for a foamie, but it would be an excellent solution for a heavier model. Worth checking out while eventhing is in the open.

I'll also try tying these shields tied together on a single "ground plane;" Perhaps trading the plywood component shelve for a thin piece of copper plated G-10 PC board stock.

Thanks for your ideas.
I'll post the results.

/pem

pemiller

Skywca,

I wouldn't have believed it without seeing it for myself: Your aluminum foil trick works great!!

I did not wrap the wires, just the receiver. I tried both a Sombra and an FMA M5; both are dual conversion. I cut a 12"x12" square of Clingwrap (plastic wrap) and repeatedly folded it onto itself, 2" wide, until I got a 2"x12" 6-ply plastic strip. I wrapped this around the receiver twice and cut off the remainder; I used small pieces of Scotch tape to close the pinched off ends of this plastic cover; the servo leads come out the end closest to the receiver's servo connector, and the antenna comes out the other end, i.e., no external wires running through the inside of the wrap and across the receiver circuitry. This plastic insulated any exposed metal surfaces on the receiver assembly. I then wrapped the receiver with three layers of aluminum foil. The combined foil and plastic add little weight and eliminate all the interference. I didn't use the ferrite bead; it actually weighed more than this solution. I experimented with various distances between the ESC and receiver; it didn't seem to matter but why temp fate: I would recommend as much separation as possible between the wrapped rcvr and any high power components, e.g., ESC, motor. A little troubleshooting before adding this shield indicated that the problem was definitely an ESC>>-->receiver issue; I did not investigate the potential effect of RF motor noise.

My hypothesis: I'm assuming this works because the foil creates a Faraday Cage (http://www.mos.org/sln/toe/glossary.html#faradaycage) around the receiver. This is similar to the Theater of Electricity at the Museum of Science in Boston (http://www.mos.org/sln/toe/). The Theater operator is safely inside a Faraday Cage that is being struck by huge static sparks generated by a giant Van de Graaff generator (http://www.mos.org/sln/toe/cage.html). [I realize I'm making a leap of faith between high voltage static sparks and RF noise; I'll research the details of an electromagnetic wave radiating an ungrounded metal cavity. ]

pemiller

Hello again,

Just tested the same setup with a Futaba R146iP PCM receiver with the case removed. No foil, no consideration of wire location or ESC-to-receiver proximity. The best performance yet!! No jitter, no glitches; absolutely solid performance.

Something to be said for these new, small PCM rcvrs!!

Doc, I'm sold!!

/pem

Woody 51

Thanks Guys,
Some great info!

Woody 51

Thanks Guys,
Some great info!

ilike2fly

My Feedback: (23)

Maybe I am just lucky. I use the FMA dual conversion receivers, the JR lite receivers, and a Berg. I have 6 ducted fan jets and 5 electric prop planes. I have never had any interference problems on any of these planes. On my F-86 the FMA receiver is real close (.5") to the speed control with no inteference. I am glad to no of an easy solution in case it happens though. Thanks guys!

skywca

Pemiller,

Yes, I was referring to the three wires from the ESC as one group. It sounds like you did exactly what I explained. I'm glad to hear it helped.

pemiller

Well, we finally finished the F-86 construction and we used the small Futaba PCM receiver with the case removed; it was the most stable one tested. Flew it the first time this afternoon. Very nice plane; very smooth performer; I didn't notice any radio hits. Not as fast as I thought; G2 got me thinking everything "jet" goes a million mph; it's fast, but you don't need to stay way ahead of it. We didn't have the decals on so that was the tough part: Is it right side up or upside down; coming at me or flying away; this part required a bit of concentration. Some detailing should help this.

Here are some pics of our baby. The only modification (in first picture) to the design was securing the elevator push rod tubes to the turbine support frame; without this epoxy the elevator control was a bit sloppy. The last picture shows the electronics in the cabin. Aft are the elevator servo (HS-55) and the ESC (CC25); the 3S1P Lipo is in positioned to set the CG just right; and forward is the PCM receiver. The antenna exits through a small hole in the bottom of the fuse and is taped along the bottom. Solid, glitch free performance.

/pem

skywca

Glad to here it worked... Looks good!!!

paeng

Hi SKYWCA / PEMILLER,

Can you post pictures of how you did the wrap of alum foil of your ESC wires and receiver. Advance Thanks.

EDGAR

pemiller

paeng,

Please standby till this weekend; I'll break out the camera and post some photos of the setup I used.

Cheers!

/pem

pemiller

paeng,

Here is a sequence of replies that describe the process I used. I'll use a receiver and a single servo to demonstrate the setup; you will probably need more electronics for the average setup; in all cases the servo, battery and ESC leads should exit the receiver wrapper together; the antenna wire should exit the opposite side; this will become clear later.

You will need a ~0.3m x ~0.3m piece of thin plastic wrap (Cling Wrap), and a strip of aluminum foil ~0.3m x ~0.05m.

pemiller

Fold the plastic wrap repeatedly until you have a multi-ply strip of plastic.

pemiller

Layout the electronics so the antenna and the servos/ESC/battery leads are stretched in opposite directions. Wrap the plastic around the receiver to provide insulation for all the electronic connections. Tape the ends of the plastic wrap. This creates a plastic "cocoon" around the receiver. Do not allow any wires to pass over the top of the receiver before exiting the end of the cocoon.

pemiller

Wrap the aluminum foil strip around the plastic wrap cocoon several times; crimp the ends around the leads. You can tape the aluminum closed, too.

Good luck. Let me know if this works for you!

Cheers.

/pem