EDF interference

[scott cuppello]

Well, for me Jeti RX is the name I see that keeps popping up there, and I must admit, after recently trying one [MPD version]....I can see why.....by jove....I think he cracked it.

[Steve Hargreaves - Moderator]

At the risk of pouring a bit of cold water onto Jeti & although not an EDF flyer yet I have a 5 channel MPD version in a Nigel Hawes Fizza & that still glitches....no where near as much as the GWS unit it replaced but it does still do it...maybe once every two or three flights. I also have a cheap as chips Cirrus single conversion unit in another leccy model & that has been perfect...no glitches at all. Although I do like Jeti stuff & they have a very good reputation at my club I think the quality of the installation is what counts most.

[scott cuppello]

I have used Cirrus without glitching [all my aircraft are electric]....Iv'e also used Cirrus with massive glitching....the same applies to other makes of reciever. The Jeti MPD doesn't, from my experience of it thus far, "cure" glitching [I'm convinced that only 2.4ghz with EDF & electic flight will do this]....but, it does stop an expensive model becoming a collection of balsa/foam and expensive parts, that will do for me!

[Alistair Taylor]

I'm going to throw a hypothesis into the mix here and see what ripples it causes;

It is impossible to come up with a cure, or anything more than a working list of "sticking plaster" type remedies for the electrical noise that causes glitching in R/C systems because;

- R/C gear (brushless motors, ESCs, RXs, servos) is too diverse (How many manufacturers? 35 Mhz 2.4 Ghz)
- the installations this gear is used in are too diverse (EDF, Helis, Foamies etc)
- R/C gear is not used/maintained in a consistent way (different brands are mixed, no two modellers subject their gear to the same checks)

and (sticking my neck out a little here)

- Some (certainly not all) manufacturers' products show varying levels of quality (some improve over time, as technology/manufacturing processes are developed, some just vary)


The conclusion I'm drawing from this thread, and the other thread on EDF glitching, is that even after you've done your best to make sure the installation is top notch, the gear is matched and checked and the power sources are all A1 (these are all things within your control), whether or not you get glitching, and to what degree, is down to luck (whether or not you got the motor/RX/ESC made at 5pm on the friday before the bank holiday) and, to some extent, budget (higher level gear is, hopefully, more likely to be higher quality, or more resistant to electrical noise, and more consistent in quality).

Am I wrong?



AlistairT

[Tentpeg]

A lot of you keep talking of Jeti receivers. I have been unable to establish who their distributors are in this country. I have learned from their website that they are made in Czechoslovakia but no other info seems available. Can anyone give some guidance please?

[Tentpeg]

Our flying site at North Berks is pretty well interference free, there have been the rare glitches, but it's debatable as to whether these didn't arise from some other source or from a maintenance problem, loose connection, black wire etc,etc. The only consistent problem is with EDF.
Any info on UK distributors for Jeti?
Tentpeg.

[scott cuppello]

Jetsome, this is interesting, our flying site has a "dirty spot", where all models are affected, however, the rest of the site is clean.

Now, I have more problems than the IC guys, which seems to be the way of EF, but EDF is far, far worse of the lot.

As I said before, just because YOU havn't had a problem, doesn't mean there isn't one, and to be honest, your point about other EDF flyers? Well, I havn't been on the forum you mention, but the guys I talk to in the states seem to accept crashing, via glitching or whatver, as nomal, a bit like the park-flyer guys....each to their own, but I don't find that very appealing. They also seem to expect evey new product to be only half thought out!

I think Alastair is spot on, sometimes certain things just don't work too well together, so, to avoid this, you can only advise people to start with what you know BROADLY speaking works.

So, I have a couple of guys looking at EDF, who have been put off, now, my advice would be, Jeti MPD reciever, as well as the usual other advice. The Jet just also happens to be about the smallest and lightest reciever I have seen...so it makes sense! Other than....let everybody else buy the new kit's....then watch the internet forums to see if they are actually any good!

[Alistair Taylor]

Jetsome

thanks for the reply.

Your input on Jeti MPD receivers has been really helpful for me.

My hypothesis was only that, something to agree/disgree with and discuss. I agree that manufaturers who have been making radio gear for years are not likely to start turning out rubbish.

But EDF, particularly the high-end stuff, has not been around for that long. The old copies of RCM&E I have from the 80s and 90s describe "jet" events where every model was powered by an IC Ducted fan, bar the odd jet turbine.

Bearing this in mind, I don't think we modellers should be surprised that when we push electronic circuitry to new boundaries in "noisier" installations at very high Watts we get problems, and that SOME manufacturers have not yet got it together in terms of compatibility and resistance to noise.

Certain reputable car manufacturers who have been around since pontious was a pilate are still prone to slip ups necessitating expensive product recalls....

Your suggestion that 35Mhz might be the weak link is interesting. I don't know enough about this to be able to agree/disagree. Wouldn't it just be our luck if the frequency allocated for model flying is particularly prone (a "blue note"?)to interference....

The site I fly at now (an isolated ex WWII airfield) also seems to have a bad spot for interference. It's above the grassy bank created when the airfield was originally levelled. Do we know what's causing it? not a scooby, we just try to avoid that area.

A couple of years ago I flew a few miles away from Heathrow, on a site shared with dog walkers, kite boarders(!), and kids on mini motos. Interference was an accepted problem, as you'd exepct with the proximity of radar/ILS/Comms systems etc etc. Most of the fliers of larger models (above 40 size) used at least dual conversion, or preferably PCM gear.


AlistairT

[Alistair Taylor]

Happy and safe flying :)

I will do a sun dance for you


AlistairT

[nasa_steve]

the mobile phone theory is absolute tosh!!! for want of a better word. i was at weston as well as a lot of the guys on here who have been endeavering to answer your questions.
my take on it is more than likely back emf build up in the battery to esc side of the equation which has nowhere else to go but straight into the receiver. this is the reason why esc's have those large capacitors on the battery side of the esc try fitting an extra capacitor across the cables on the battery side of the esc its worth a try it will need to be the same size or smaller than the one thats already there.
regards
nasa

[Nick Chudley]

Here's something I've proved to stop glitching and it cost me nothing.

Keep the servo wires well away from the ESC. They pick up glitches just as badly as the receiver and the arial, in my experience.

Flying wings are villains for stuffing all the wires into a small space together and that's how I proved it. My other planes weren't doing it, though they used the same cheap GWS kit (with and without brushless motors).

I tried moving the arial and receiver without success. As soon as I moved the ESC into a little space of its own, the Wild Wing was transformed, and flies like the proverbial bat out of hell now. Brilliant fun! It only uses an ordinary brushed 400 motor.

[Tentpeg]

If you look at the installation in the Fantom, you will find that the ESC is set into a recess inside the fuselage and is quite a reasonable distance from the Rx and servo wires so I don't think this is a factor with this particular model. It certainly glitched fairly consistently, but unpredictably enough to render it to tiny pieces.

[Nick Chudley]

Well you have certainly provoked a learned discussion!

I bet you find a low-tech solution to the problem. How about CF rods in the airframe? I've often had trouble from intermittent faults with RX crystals or curcuit boards after one or two crashes. Have you tried anything with the unit that was in the Fantom since the final demise?

I've used several different inrunner and outrunner motors without noticing any special tendencies. Maybe the very high revs in EDF cause a problem. That should be testable because normally, running a motor at half speed causes more interference than full speed. When I do my range tests, I always try it both ways. (provided there's someone around to hold the plane!)

It's certainly true that some spots in the landscape are blackspots. But you mentioned "consistently but unpredictably" which seems to rule that out.

Better luck with your next try!

[nasa_steve]

jetsome
with all due respect my information comes direct from J Tinka one of the founder's of JETI you may have heard of them they make esc's and electronic equipment for the modeling industry. i discovered first hand what extending battery cables can do to the flight pattern of some electric models. it does'nt always happen but when it does its normally occur's in higher powered applications. i had some very long e-mail chats with mr tinka and he kindly sent me some capacitors with which to try. beleive my this transformed the model and i now use (to great effect) this same system in every model that i am forced to extend battery side cabling in a model.
you mention "Back emf occurs when an inductance sees a a steep change of emf (voltage)" so when an esc switches to the next pole in the motor does this not cause exactly that??? i can assure you JETI,CASTLE CREATIONS M'TRONIKS etc are convinced it does and not sure which of these done the research but voltage surges/spikes in the region of 30volts have been recorded building in the cables (battery side).
my knowledge comes from the model industry and from trying out these things i do try to avoid extending battery side cables as i can cause these glitching problems but when i have done it i've always added capacitors in line to control emf build up the rule of thumb that the jeti guys told me is the esc alone allows for 200mm of cabling (battery to esc side)if you intend to increase this you must add the same value of capacitors that are already on the esc for every further 200mm that you extend. this has worked for me and i have tested with caps in and out and the caps in does stop the glitching from the esc side of the equation.
nasa

[Tim Mackey]

Ah but Nasa....you forget.....most of this so called glitching is not glitching at all, 9 out of 10 of these problems are down to poor installation practice and sloppy linkages :)
http://www.modelflying.co.uk/forum/forummessages/mps/UTN/726/dt/4/URN/1/srchdte/0/cp/2/v/1/sp/

[Alistair Taylor]

Nasa_Steve

thanks for the info. I've had to extend the cables between the ESC and motor in one of my planes, and I've been a bit concerned about interference. If it's the battery end that's critical, I should be OK. Although what about the homemade packs with longer than average leads.....

Something I read (somewhere...sometime, can't remember where/when now) was that the old (ancient?) style of servo cable that was made from plaited, rather than bonded, strips of wire, was less prone to interference.

I've plaited the extended motor wires in the plane mentioned above, but I don't know whether this is based on any firm theory or not.

AlistairT

[Tim Mackey]

"twisted" wires as opposed to flat "side by side" are better at reducing potential interference. Seems they kinda cancel each others problems out better by being "wrapped in themselves" and bit like shielded cable in so much as its better at ...well.....shielding.

Timbo stands back and waits for the pedantic and purist police to charge him with a heanous crime of simplification :)

[Alistair Taylor]

The Pedantic Police and Purist Police have merged to become P, following a multi-billion pound re-branding exercise.

Of all people I would have thought that you'd know this Timbo

;)

Alistairt

[Tim Mackey]

LOL

[Nick Chudley]

Here's a good web site on this subject..

[nasa_steve]

timbo
i have found that twisted servo cables are better as it tends to cancel the parallel paths which do not help i also twist the motor wires together as well this has i think helped in eliminating glitching.
regards
nasa

[Tony Jones]

Alistair
Thanks for the tip about the Mtronics glitch buster gizmo. Until now I've used SM Services full house opto to isolate all servos and the ESC from the receiver. But as the ESC seems to be the main suspect in backfeeding junk to the receiver, the Mtronics unit on its own might be just the ticket.

[Steve Hargreaves - Moderator]

Slightly off message here but may be of interest...in my professional job (the one that pays the mortgage rather than provides the enjoyment!!!) I am currently working with a company designing a drive system for a Hybrid car. This has a control unit between the motor & battery that controls the charging & running of the motor...much more complex than our motor/ESC/battery combo obviously but the parallels are there...& they are having huge problems with EMF, spikes & glitches interfering with the many electrical systems on the car. Their solution is to use individual shielded cables (like a braid wrapped around the conducting core) & ground all the braid to effectively "trap" the electro-magnetic radiation.

[Tim Mackey]

yes I have tried that idea in the past, using screened co-ax cable ( TV aerial wire basically )and grounding all the shields to battery negative. Helped a bit, also tried wrapping some "earthed" outer braid around the servo leads and this helped a little......the addition of ferrite rings at the receiver end also helped, BUT I still suffered the odd small glitch in one particularr model, but as I said earlier only the move to 2.4 has been the real answer for this model.