Glitches when using 35Mhz with electric

[Bob Moore]

Oh well, after faffing about trying to get the rather large old dual conversion rx in, I've given up and ordered a single conversion Corona 6 channel rx from GC and a GWS micro half size crystal from Micron RC. (Hope it's the right Xstal as it's cost me a tenner with P and P!)

 

At least the Corona is small enough to fit a bit further away from the esc and gives me a chance to put a couple more ferrite rings in.

As I said before I've two small leccies and get no glitches with them, so I wonder if its the biogger esc in the Wot that radiates more interference. Watch this space!

Edited By Bob Moore on 10/09/2012 10:59:39

[John Muir]

Hi Bob,

Just got back to this. The reason GS is out of channel 70 mini crystals is that i bought their last two just over a week ago, along with a couple of the Corona receivers . The mini GWS ones should be fine though.

On the subject of servo interference I once bought some very cheap DYS servos from GS and they caused feedback to the receiver which shortened its range considerably and caused terrible servo chatter when the limit was reached. Luckily I spotted the problem when range checking and got a refund no problem. Apparently there was a a design fault in these particular standard sized servos. So always worth checking every link in the radio chain if there's a problem I guess.

Banning 35Mhz? I certainly hope not, there are an awful lot more failures on 2.4 equipment at our club than there are on 35. Or maybe 35 MHz pilots are more honest about what made them crash? I don't know.

[Former Member]

[This posting has been removed]

[Simon Chaddock]

I would agree the ESC can be an issue on 35 MHz.

A plane in its original configuration due to extreme lack of space had the ESC (30A) and radio literally side by side. The servos are wing and tail mounted with long extension wires.

No interference problem at all and with a range as far as I wanted to see.

Eventually overloaded the ESC so replaced it with a 40A and during a bit of a rebuild moved it as far apart as possible from the radio, about 6", with longer battery leads and shorter motor wires.

Result? no end of glitches when under power but ok when gliding. Changed the motor, the radio and the run of the aerial. It made no difference. My suspicion fell on the ESC although it functioned perfectly.

In desperation I returned it to close to its original configuration of motor and a new 30A ESC right alongside the radio. No glitches!

Maybe the 40A ESC was poor & radiated badly. Maybe the 30A is simply better or maybe in a close side by side configuration its heatsinks actually provide shielding to the radio just a few millimetres away.

I have other planes with the ESC and radio in a 'tandem' layout that give no trouble!

Edited By Simon Chaddock on 10/09/2012 11:53:37

[Bob Moore]

Interesting responses about 35 mhz being banned! I agree, I think there would be some uproar if it was tried at my club.

ah, it's your fault John. No problem really as it seems the GWS ones are ok to use and Micron RC appear to have mine in stock.

RE ESC's , when I modified my Wot 4 to leccy there was little choice about where to place stuff. The esc is quite big and chunky and the wiring heavy so it had to sit behind the motor and above the battery which is as far forward as it could go to achieve CoG. My only option is to move the rx back and maybe sit it above the servos? Or even in the rear of the fusi behind the servos (which will require some surgery.

I'll explore the idea of changing servos if necessary. But I plan to fit ferrite rings in those leads too.

Edited By Bob Moore on 10/09/2012 12:13:41

[Pete B]

Posted by Simon Chaddock on 10/09/2012 11:49:15:

In desperation I returned it to close to its original configuration of motor and a new 30A ESC right alongside the radio. No glitches!

Maybe the 40A ESC was poor & radiated badly. Maybe the 30A is simply better or maybe in a close side by side configuration its heatsinks actually provide shielding to the radio just a few millimetres away.

It's possible that changing from 30A to 40A ESC's resulted in going from a linear-mode to switch-mode BEC. I tend to use Hobbywings and they are all switch-mode from 40A upwards, linear-mode 30A and lower.

It has often been reported that switch-mode BEC's generate more interference than linear, so your experience may bear that out, Simon.

Pete

Edited By Pete B on 10/09/2012 13:01:59

[Peter Beeney]

Bob, - A colleague bought a couple of the Corona 6 channel single conversion DSP receivers when they were £12 each. He tried one in a notorious (for glitching) electric model, result - total 100% fix, and I tried one in a i/c hack for things like low level long range performance. Also a complete success. These used standard Futaba crystals, it’s possible Hitec may not work; the receivers were just pieces of PCB, so the crystal tended to stick out considerably which I though was a bit of a liability so I soldered short bits of copper wire at right angles on the crystal pins so that it laid flat on the board and held it with a turn of insulating tape, as always. Perfect! I also changed the cotton like aerial for a piece of proper wire. I still use mine but my colleague is now 2.4.

I don’t think we will ever ban 35 MHz, we don’t make those sort of rules. Sounds a bit like that guy Jobsworth is getting abroad again. Difficult to see on what grounds this could be justified anyway.

I think the Digital Signal Processing bit means the signal is zipped through a micro processor which will allow any genuine signals to pass through but will prevent any rubbish getting to the servos. If they get total interference, a same frequency tx on, say, they just stand still. But you really couldn’t expect much else.

Good Luck.

PB

[Bob Moore]

Interesting. The reviews on it are excellent I must say and it does read as though they have improved signal processing. I've already bitten the bullet and bought a crystal reported to work on the basis of why risk a couple hundred quids worth of model for the sake of a tenner! ( I was half tempted to try a standard Hitec one though.)  Last flight it involuntarily did a roll while climbing, (big aileron glitch) don't want any low level glitches that pile it in

 

I'll find some way of securing the crystal as reviewers did mention it was a bit vulnerable.

Thanks

Bob.

Edited By Bob Moore on 10/09/2012 13:50:03

[Bob Moore]

Good service from Micron RC who posted 1st class today. They appear to have most channels in stock in type GWS, etc. if anyone else is looking for a crystal suitable for a Corona rx.

[Former Member]

[This posting has been removed]

[Frank Skilbeck]

Posted by Andrew Ray on 10/09/2012 22:04:15:

I seem to remember that the general rule some years ago was that it was ok to lengthen leads from the ESC to motor but not the battery leads, they should be as short as possible. Sounds wrong as one would think that noise would come from the motor leads. Anyone else remember this?

Thats to protect the ESC not to reduce noise. If the battery to ESC leads are too long at high amperages you can end up overloading the input capacitors.

[Bob Moore]

I thought it was the other way around (ie lengthen battery leads) because of back emf's from the motor affecting it's performance?

Edited By Bob Moore on 10/09/2012 22:32:00

[Simon Chaddock]

There is definitely a restriction on the ESC to battery lead length.

It is not a fixed figure but the longer they are the more likely the ESC's smoothing capacitors will be damaged by induced voltages. It is possible to add repeat line capacitors if it has to be very long..

There is no such restriction on the motor to ESC leads other than the eventual voltage drop.

Pete B

You may well be right about the bigger ESC having a switch mode BEC as my son came in from an adjacent room and asked what's that high pitched wine although it was completely silent to my old ears!

[Bob Moore]

Sorry my mistake, I was having a grey moment!

There's a thread on it here on RC Groups.

Bob

[Allan Bennett]

When I was on 35Mhz with my e-conversions I eliminated interference by using an opto ESC and a separate NiMh receiver battery. Maybe not feasible if space is an issue.

As for interference sources, I believe the main source is the ESC and motor, and their connecting power leads. But interference can be induced into any low-power signal leads that are close to and parallel with the power leads, so can get to the receiver via any poorly-positioned servo lead. So ferrite rings on servo leads might help.

[Former Member]

[This posting has been removed]

[Bob Moore]

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@Tom. TX works well with all other models so I think it's OK.

 

Report on my Corona experience. Not a good one!

Tested the Corona Single Conversion RS610II Receiver 35mhz on my sometimes glitchy leccy Wot4. First plugged in the Micro RX GWS crystal from Micron. Then all other connections, being careful not to get polarity wrong as it can blow the thing up apparently. Nada. Zilch . No response whatsoever. The esc just bleeped to say I'm not getting any info. ie the motor will not respond and elevator, etc won't work. The crystal is a very loose fit in it slot so I bent the pins slightly inwards to make sure it was making good contact. Remade all connections and it worked. Rudder, elevator and motor. Turned it off and on again and zilch again. (I'd already decided I wasn't going to fit this rx?) But maybe it didn't like the crystal I thought. (GWS micro is reported to be OK with this rx.) So I tested a Hitec one by holding it carefully against the crystal socket. It worked so I soldered a couple of small copper wires to the Hitec Xstal and soldered it to the VERY small contacts in the RX. Very fiddly job. Plugged it all up again. Nada. Pulled all servos off and tried and there was life? It connected, the bleeps said it was OK and the throttle ran the prop up on the leccy. So this Crystal does work ok anyway and my soldering was good.

SO I reconnected the servos and zilch again.

Just to be sure it had an intermittent fault I plugged it all up in another model and powered it by a normal RX battery. Still working intermittently. So that was a waste of £15 or £20 for the RX and Crystal (with P and P). I think the thing has a processor problem or poor solder joint somewhere.

Incidentally, the pins are very close together on these RX and I had to file down the servo plugs a bit to slim them down as if not they are very very tight.

Put the old Hitec Dual conversion RX back in my leccy Wot4 and it ran straight away, so I feel the problems weren't with the model. I think I'll go with the Hitec, and the Corona is going into the bin.

I've had a good look at the circuit board and can't see any obvious poor solder joints. Maybe I was just unlucky?

Edited By Bob Moore on 13/09/2012 14:10:07

Edited By Bob Moore on 13/09/2012 14:14:33

[Bob Moore]

Not being one to give up easily I did a few more tests on the Corona rx. Soldered the GWS crystal on and tried it with the Wot. Same thing, sometimes working next minute not.

So I tried it with a different tx. No joy at all.

So I tried plugging in a battery rx battery pack and 3 servos, and lo and behold it worked , for a couple of minutes or more and seemed ok. So I plugged it back in the Wot with the external servos plugged in and powered by the BEC. Nada.

It just has a bad joint somewhere, at one point it was working and when I was handling it, it stopped working.

I give up. What can you expect for a few quid?

[fly boy3]

Hi Bob, I got over the constant unavailability of crystals by purchasing Corona synthesized receivers, these have no crystals, therefore eliminating one extra possible problem point. Cheers.

[Bob Moore]

Thanks. I did try it with two different crystals though. The reviews were good for this rx, but maybe I was just unlucky? Think I'll stick to Hitec. I've installed an old Hitec dual conversion rx, with some extra ferrite rings here and there, and sat it on a piece of aluminium foil to seperate it from the esc and motor. I'll see how that goes?

[Andy Gates]

Bob

Can you try one more thing before you give up on your reciever.....please?

Remove the red wire from the connector from your ESC to the reciever, and plug in your reciever battery pack and retest it.

I am wondering if you have a crack in the red wire from your ESC so maybe that might explain the hit and miss connection you are getting. If this is the case then any reciever could go in and out of connection during flight which will not be good for the model.

[Bob Moore]

Thanks for the suggestion Andy and I did wonder that too, so I took a look at the lead from the ESC. However, if there was a fault in the feed to the rx it would display the fault with every rx I put in. The Hitec has been in and out a few times in between trying the Corona and it works 100 % every time. Plug in the feed and the servos and it works, just the way things are supposed to.

Plus, the intermittment fault has occured when it's plugged completely seperately into a NiMh battery pack and external servos. I'm 99.9% sure it has a fault on the board. Tried different battery, different tx, different crystal, different servos! And it still only works intemittently. Very annoying. Even if it appeared to be ok in another test, unless I could see where the fault was and sort it, I would never trust the thing.

Edited By Bob Moore on 13/09/2012 19:38:25

[John Muir]

Bob, I'm with Andy, I'd seriously consider a problem with your esc or connections. The Hitec receiver works a bit, but not 100%, and the Corona doesn't work at all probably because the clever DSP circuitry is filtering out the dodgy signal completely. Maybe the Corona is safer 'cos it won't let the model get off the ground?

[John Muir]

Sorry, cross posted.

[Stephen Jones]

Hi Bob ,

I had problems with interference on a small 35Mhz receiver so i wrapped the Esc and motor wires in foil and have never had any problems with it since . And it is on a small converted glider that my son flies it has even had half its aerial cut of and still no problems and we have had the plane so high in the sky you could only just see it . There is even a video of my son flying it on you tube .

Give this idea a go .

See how close all the gear is and nothing around the Rx .