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Motor wires too close to Rx??

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Old 01-23-2005, 04:01 AM
  #26  
jooNorway
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Default RE: Motor wires too close to Rx??

Yesterday we were 15 pilots flying indoor in a gym with a lot of metal in the roof. Surely grounded through the building-core. 6 planes were airborne on the most, sometimes it all worked well, and sometime we all did have a lot of glitches. I should have brought a good frequency-analyser logging what happened when we got trouble This time it might have been mix-products.

I think the most trouble I have seen happends when we/others don`t fly their big birds on our local runway but when we take our foamies to a local fotball-field. All the man-made constructions in the surroundings causes trouble. An other factor is that we use lightweight (and sometimes) cheap receivers. These do surely not have the same quality at the components surrounding the heterodyn-curciuts which themselves make spyrious. The filters around the conversion-circiuts are essential for the quality/range/suppression for the RX. For example the Hitec Feather is wellknown as useless, at least on the 35-band. Could it be better at 72MHz? Unknown factors...

The fact that pilots do use such variety of frequencies around the world make me think: could it be that some ESC-producers don`t take care of this when they construct and test their electronics? This is the reason why I think it is time to take a close look at several brands. The problem is that I need to borrow some ESC of brands I don`t have myself and I should use the expensive analysers at work and not the field-type. And I need time... My work sends me around the country the most of the time, 12 days working and two days at home. But this discussion have triggered me to go for a test as soon as I get the time Great.

Talking lobes; when you fly in the weak part of the lobes and a subject is reradiating the signals you COULD get points of worst case fading the signals below the receivers input sensitivity. These points are not static since we usually move on ourselves so therefore the problems occur to be coming and leaving. Of course a good check using expensive equipment and skilled people can tell... but this is a hobby.

An example form my work; When testflying an InstrumentLandingSystem (ILS) the glidepath gave a significant bend causing the autopilot to give a "jump" on landing-sequense. The systems and of course the reflective area in front of the antennasystem vere checked and checked. Then there vere ran a computersimulation on the problem pointing out that there had to be some reflective object in a certain area. And the "object" vere found exactly there, a metal-roof 5 kilometers from the end of the runway A combination of high effect from the antennas in that area and the size of the roof.

A good way to think about these magic is to look at the signals radiating from our antennas as light. Then think that you sit on your plane reading these light-codes, and suddenly you see light from other objects which reflects the light from your antenna... Getting confused? Your receiver will be too.

I have a slightly feeling we have got very far off-topic, but some of us are extremely interested in this, don`t you think Ben? Anyway, this is an extreme nice hobby no matter which part of it we like the most

There are more between heaven and earth than foamies...
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Old 01-23-2005, 02:47 PM
  #27  
RickAvery
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Default RE: Motor wires too close to Rx??

Wow, does this stuff get deep? Well I tried to reconfigure the electronics to no avail. With a motors on, 1/2 throttle, she would start to glitch at about 350'. Motors on and off, and both servos jumping. The equipment I'm using isn't the top of the line by any means, but I've been using this same stuff on several different planes flying in this same area without this kind of problem. It's a Hi-Tech 72mhz, AM, 3ch single conv. radio and receiver. Between my bro-in-law and myself, we're flying 7 different planes/wings with nary a glitch. Now I'm thinking two things. The equipment I'm using is fine dealing with the noise created by one ESC/motor, but two of them is too much, Maybe a dual conversion set up would help, or the possibility of maybe having a bad Rx. It's brand new but there are bad ones. So I'm going to start swapping components and see what happens. Thanks to all for contributing to the discussion, and while I admit to only being able to follow about 10%, this IS helpful and appreciated.
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Old 01-23-2005, 04:51 PM
  #28  
Ben Lanterman
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Default RE: Motor wires too close to Rx??

Rick you are taking the right approach, do change out the receiver only but keep the antenna with the same routing. That way the only variable is the receiver (and well the transmitter as well).

However since the servos are jumping with or without motors on then you can almost eliminate the motor noise as a problem. It sounds like a pure range problem which changing receivers would check.

I have a 3 channel Hitec that I bought 5 years ago as my first 72 mh smaller rig. I had been using old old 72mh rigs when we had the 6 channels and then some 50mh rigs - all big old equipment. I just took a look at the receiver - it is a big brown setup with green label that has AM embossed in the plastic where the 4th and 5th channels would go in the newer Hitec 555 receivers.

I don't know if it is dual conversion or not - it is buried under the servos and battery plate in the airplane, all I can see is near the servo plugins and not the info written on the top of the receiver. I don't know if it is the same as your setup or not. One thing though is that it has range as far as I have ever flown the airplane (which is pretty high).

Every month or so I fly the airplane several hundreds of feet high so it is small but I can see how it responds, collapse the antenna and point the antenna at the airplane. That assures you getting the lowest signal at the airplane and have time to pull out the antenna and recover from the maneuver (no doubt a straight down full power dive) if the rig isn't working.

350 feet is pretty poor range. Check that each motor has a arc suppression capacitor on it. Wait, you said it was working OK with one ESC/motor but with two motors it isn't working. You need to determine if it is a receiver or ESC problem that isn't happy with two motors for some reason. If all you varied was adding a motor to the ESC and found yourself with no range then it would seem to be motor ESC oriented. Disconnect one motor and see what happens to the range.

But do change out components until you find a reason why it worked before with one motor and doesn't now. And be sure and report back the results.

Side comment, With the old Hitec (before I went with Futaba equipment) I decided to see how many motors I could fly on one of my stick and foam models (I had an open field just across the street). I had some very small surplus motors that had good brushes on them. I ended up with 6 of the little motors in parallel across the wing on the same ESC and it was a medicore success at best. I never had a range problem as it would make one small circle around the field and run out of power!

I agree jooNorway, the need to make the receivers light and cheap does cause a lot of compromises in the design. There are a some manufacturers using single conversion in their top of the line radios but they are using the top of the line signal processing techniques also. It makes a difference for sure.

My dad was an electronic tech for the FAA and several times took my brother and I out when he had to make an emergency run to fit the ILS system that was around 45 years ago. No computers to make simulations though!!
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Old 01-24-2005, 11:18 AM
  #29  
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Default RE: Motor wires too close to Rx??

Ben,
Thanks for the vote of confidence. I think maybe I didn’t make my point clear regarding the twin motor set up. The point was that I’ve used this same 72mhz, 3ch AM set up for many different planes/wings both brushed and brushless single motor applications and had as much range as I dared to fly. All of the motors I’m now using are brushless, so I don’t think that having cap suppressors is applicable. With a twin brushless motor set up, it requires that each motor has its own ESC. So I’m running 2 CC 25amp ESCs with a ‘Y’ connector to plug them both into the Rx. Never had a problem with single brushless motor & CC 25amp ESCs, but maybe the set up or the noise generated by two pairs of ESCs/motors is too much for the cheapo Rx to cope with. Also, this is my first time using Hi-Max motors. I have mega & astroflight motors which work fine, but my bro-in-law is running a single Hi-Max (same Tx/Rx), with no problems. X-tals can also be a source of problems usually after a hard hit. I’ve ordered a new Rx and will start swapping parts and running range checks. I just re-read your post and The last time I did a range check it was with the motors at ½ throttle and when the motors started glitching, so did the servos. I’ll try it again tonight without the motors on and see if the servos glitch by themselves. Thanks again for your time, insight and ideas. Happy flying!
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Old 01-24-2005, 12:16 PM
  #30  
Ben Lanterman
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Default RE: Motor wires too close to Rx??

Now I see - Rick, that was a great explaination. Indeed it would seem to be the ESC's as jooNorway said, I should give him credit for that. I personally am learning a lot to with you doing all the work! Thanks.

I have to wonder why with two instead of one, of course you get twice the signal strength from two but it would imply that one should be glitching not too farther out than the two given the nature of the way the signal decreases from the transmitter.

Since you are running the receiver through both of the ESC's then there might be something due to the fact that there are two separate power supplies from the ESCs trying to supply the receiver that don't work well together - but that is snatching at straws. Do the range tests with everything in place and unplug each ESC in turn. See if it is a particular ESC that is having a problem with noise. If both work individually then it is the combination that is the problem.

I have a servo driver used to check out servos. You plug in a receiver power pack and a servo and check them. When I was using it to drive an ESC to check a new brushless motor it was starting and running erratically. I removed the "receiver" battery pack and let the ESC provide the power for the servo driver and it worked fine. Maybe something like that is going on.

The crystal can be a problem but it should be consistently bad no matter what motor/ESC you are using.
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Old 01-26-2005, 09:54 AM
  #31  
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Default RE: Motor wires too close to Rx??

Well, I finally got to do some more experimenting with the glitch monster. I received the new receiver and installed it. Routed the antenna as before and did a range check. I powered up the electronics, checked out all the functions at close range, all was well, and started walking away. At ~ 400’ I stopped and moved all control surfaces, all worked as expected. Then I powered up the motors. GLITCH CITY!!! Motor power going on and off, and servos twitching. Darn!! Back to the hanger and disconnect one of the ESCs from the ‘Y’ connector. Glitching slightly less but still very present. Same senerio for the other motor with same results. Swapped crystals from a plane that flies fine. Same results. I’m bumming out now!! Final results; I’ve tried the tests with two different Tx’s, on two different channels, 32 & 46. With two new out of the boxes Rx’s, with both motors running & with each motor running separately. Routed the antenna three different ways. Checked all of the connections and all appear fine as the functions all operate properly at close range. I’ve done these range checks in two different locations on the property, opposite directions. In-between all of this frustration, my bro-in-law and I are flying all of our other planes in this exact same area with nary a glitch. ?????? I guess I’ll have to bite the bullet and order a real dual conversion Tx & Rx. It was going to happen sooner or later as I’m sure that with the next project or so, I’d be needing the added channels. And with the hanger slowly filling up, a nice digital Tx which remembers the trims of several planes is appealing. So I’ll be Tx hunting and will let you all know how it turns out. One thing will be certain to happen. My wallet will be a sh*#load lighter!! Haaaaa!! Happy flying!! & thanks to all for your input.
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Old 01-26-2005, 10:54 AM
  #32  
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Default RE: Motor wires too close to Rx??

That is a boat load of interesting results! I am impressed at the engineering like approach you took to the problem. I can't think of anything else to try.

What would appear to be happening is that the motor/ESC are feedbacking a signal into the receiver either into the antenna or through the leads. The transmitter signal is very strong close up and overpowers the interference. Then as you walk out the transmitter signal lessesn and the motor/esc signal takes over. Since each one is putting out the same signal it explains the single motor/ESC getting more range than two.

If everything else is working fine than it has to be in the motor/ESC combination. I would email the motor and or ESC manufacturer and see if there is anything they could suggest. The last thing you need to try is to not use the ESC to power the receiver. I think (don't know for sure) that you can disconnect the red wire going from the receiver to the ESC. That leaves you with a signal lead and the ground. Run the receiver off of a separate battery pack. Then see if you are getting the same range problem.

There might be a signal isolater that you could use. I have seen them - you just put them in the leads between the receiver and servo or ESC and they optically decouple the two. I believe they are fairly cheap.

I don't know if a dual conversion receiver is going to help in your case. Do email the guys and see if they have a clue.

One last source of info is the Power Systems forum on e-zone. There are a lot of guys making and selling motors on there and some guys that I consider experts in the field that might be able to help. Tell them what you have done like in your last post and see if there are any suggestions. I know that some of them have had successful dual setups going.

http://www.rcgroups.com/forums/forumdisplay.php?f=13

best of luck and report back on any successful solutions you get. I plan on trying a dual machine in the near future so am very interested in the results.
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Old 01-26-2005, 10:58 AM
  #33  
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Default RE: Motor wires too close to Rx??

I just found it (maybe) on the power forum and they had the same dual question.

http://www.rcgroups.com/forums/showthread.php?t=327152

They said to cut the red wire going to one of the ESC's. Cutting is a little harsh. Get a short extension and cut the wire in the extension.
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Old 01-26-2005, 01:02 PM
  #34  
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Default RE: Motor wires too close to Rx??

Ben,
So is what you are saying is that because the Rx gets its voltage from the ESC, and in my current set up, I’m mixing the Rx power from two sources, (the two independent ESCs). Maybe there is some voltage mis-match or confusion, if you will, by the Rx trying to decipher two slightly different signals stuffed into one input. And, if I disconnect one of the sources, cut the red, center wire from one ESC, then the Rx will be getting power from only the other ESC maybe eliminating any crosstalk?
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Old 01-26-2005, 01:16 PM
  #35  
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Default RE: Motor wires too close to Rx??

If what I have read is correct, yes. Apparently it is a problem with two ESC's brushless or not. However the problem remains (now that I have thought about it some more) it would still give you the range of one ESC/motor which wasn't all that great.
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Old 01-31-2005, 12:43 AM
  #36  
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Default RE: Motor wires too close to Rx??

Well, after listening to the advice and ideas here and in a post on the other RC site, I was convince that the ole trusty AM 3ch radio just wasn't up to the task of dealing with the noise generated by twin brushless motors/ESCs. I picked up a 6 ch FM radio and receiver and installed it. Did a range check without a problem or any glitching of any kind. Right on!!! Time to try her out. I threw her in the air and man did she rip!! No glitching at all!! Now this is getting fun. Thanks to all for your time and ideas. The interaction was fun and educational. Happy flying!
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Old 01-31-2005, 01:51 AM
  #37  
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Default RE: Motor wires too close to Rx??

Indeed I learned a lot also. And I will try the brushless duo thing also. It seems a good way to get thrust without using one big motor with the big prop costs, etc. Outrunner Brushless makes the mechanical problems go away!
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Old 01-31-2005, 08:59 AM
  #38  
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Default RE: Motor wires too close to Rx??

Oh. I forgot to mention that I did disconnect one of the ESCs power wires, so I'm powering up the Rx with just one input. Thanks again.
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Old 02-01-2005, 10:19 AM
  #39  
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Default RE: Motor wires too close to Rx??

This thread should be put at the top as a good example of how to track down problems and having you do the work is great! No doubt the extra ESC wire is the main contributor. It could be that in a lot of cases being blames on antenna routing that it is something else. Not too many guys have the fortitude to go through the work to really track down what the problems are. Well Done.
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