Motor Capacitors

[Rodd Perrin]

I have flown my Dumas Kestrel a couple of times recently and I appear to be getting a number of "hits" where the model bucks suddenly for a split second and then returns to normal after that. I am using a DC1717 w. 11:1 gearbox, a JMP HF9, and a JR500M rx (which I also use on my other models without a problem!)

The Question - Do I need supression capacitors on the motor and if so, what size?

All help would be greatly appreciated.

Thanks

Rodd

[jimwalker]

I'm interested in the answer to that question too. I'm flying a tiny with the same motor and ESC with a Hitec feather reciever. I know the reciever works fine, I've used it in other planes with no problem. I don't have any caps on my DC1717 either because I thought coreless motors didn't need them. I finally got to fly my tiny for the first time a few days ago and experienced the same problem as Rodd described. The flight ended when the plane suddenly corkscrewed into the ground. The damage was minor and the plane is already repaired and ready to fly. However I am unsure what to do about the "hits".

Thanks....

[Jason Nowell]

Well Guys, I'll tell you what I've learned about the "hits". First of all, location is most important. Neither of you specified whether you were flying indoors or outdoors. For indoors with several planes in the air, I have even had it happen to my HiTech 555 Dual conversion reciever. We fly in a metal building with steel girters and beams running all over it. We also notice more hits when the AC is running, and the fan motors are right by our airplanes.

Also, many time my Lupo's will power off the engine momentarily when I fly over some of the high powered PCM transmitters. One has a Feather and the other a GWS PICO.

I think a capacitor would be worth a try, but I wouldn't expect it to cure the problem on single conversion recievers. If I were going to try it on a 1717, with my limited experience, I'd probably try a # 103 or 104. I've been told that just one across the positive and negative terminals is all you really need but who knows.

Somebody correct me if I'm wrong, an electronics geious I am not :)

[Rodd Perrin]

There is always something that you leave out of a discription of a problem (even when you try to cover everything!!)

The hits I was receiving were all outdoors, in the middle of a large paddock, with no one around. When I flew my S400 planes before and after the test flight, they did not get any interference and the same receiver was used in all cases.

I tried rerouting the aerial from down the fuselage (thought that the CF tube and push rods may be causing the interference) to out along the wing (mid-span, with the end of the aerial looped around the tip rib to keep it out the prop). I was hoping to get the chance to try the model with a GWS A motor (other recommended power source) to see if I got the same problems.

What size are the #103 and #104 caps? Are these part numbers (whos)?

Thanks for the input so far - I think that we are getting somewhere :-) I do not feel happy flying the plane in its current condition :-(

Rodd

[Jason Nowell]

Rodd:

I understand :) Now that you've told me that you're flying outdoors by yourself, the problem gets a little easier. Or at least we can eliminate many of the potential causes.

The capacitors I referred to are from Radio Shack. I bought a "Resistor Pack" that had 10 or 12 different kinds. The ones that came with by Wattage B-2 motor (n-20 was a 103 and my Potenski POT02 came with a 104) The numbers are printed right on the capacitor itself. 103's and 104's are pretty popular, I also pick them up at Fry's and Electronic Storeslike All Electronics
( www.allelectronics.com (http://www.allelectronics.com) )

I'm still not completely sure if you need one on a coreless motor though. Wish an electronics genious would get on here and help....hint hint :)

[ifaberman]

Guys:

Any time there is an electrical arc (like those of the brushes of an electric motor), there are all sorts of interesting radio emissions. Whether these were the cause of your glitches or not, it pays to suppress them. Many times, a smaller value capacitor is better than a larger value when it comes to radio suppression. I'd try a 103 also known as a 0.01 microfarad cap. The very small, multilayer ceramic types found around the hobby are good enough. I suggest that you try 2 caps. one from each motor terminal to the case. Be thorough, but cautious about soldering to the motor case. Overheating can melt nearby, internal plastic parts, etc. Many motor cases are plated and must be scraped or sanded first.

[ 06-26-2001: Message edited by: Quacker ]