Stuart Ord Posted January 19, 2012 Share Posted January 19, 2012 I've got a CRRC PRO GF26i 26cc spark ignition engine in a model with a Spektrum 7000 receiver. When I start the engine, a couple of servos chatter and wander from extreme to extreme. This stops as soon as the engine stops, so clearly is a vibration or interference problem. Rapping the top of the receiver or the servos doesn't cause the servos to budge, so I'm thinking it is interference, although why only 2 of the 7 channels I don't know. Does anyone know of how these ignition units can be suppressed? Thanks. Quote Link to comment Share on other sites More sharing options...
Peter Beeney Posted January 19, 2012 Share Posted January 19, 2012 Stuart, Might I just ask you, please, in the first instance, where your ignition battery is in relation to the receiver pack, i.e. are they both in the fuselage for instant? It’s possible, from past experience with 2.4 MHz, this might be relevant, or though not necessarily so.PB Quote Link to comment Share on other sites More sharing options...
Stuart Ord Posted January 19, 2012 Author Share Posted January 19, 2012 Peter, thanks for that idea. My two battery packs are next to each other. I'll try moving them. Quote Link to comment Share on other sites More sharing options...
Stuart Ord Posted January 19, 2012 Author Share Posted January 19, 2012 Peter, you're a genius. I moved the two packs apart, and the problem reduced a lot. However I'd placed the two switched next to each other on the side of the fus. So I removed the spark unit one and got it further away as well, and the problem disapppeared. I'd never have tought of that! Many thanks Stuart Quote Link to comment Share on other sites More sharing options...
Stuart Ord Posted January 19, 2012 Author Share Posted January 19, 2012 The dodgy typist meant "two switches", and I don't have a foreign accent (I tink) I've got a Polaris too - fun off water! SO Quote Link to comment Share on other sites More sharing options...
Peter Beeney Posted January 19, 2012 Share Posted January 19, 2012 Stuart, That was fast work, I’m very pleased it did the trick, and thanks for your reply. It’s a pleasure to help. If only all the gremlins were as easy to banish! Genius is only one of my lesser claims to fame, usually I’m expected to perform miracles on a regular basis. Although I guess just getting lucky, and some previous poggerings with this stuff is much nearer the mark; I’d be inclined to stuff the ignition pack in the cowl if possible, as far away as you can get it. My explanation is this, although it may not be correct, of course. - I don’t think any radio interference is likely, 2.4 MHz is a fairly high frequency and I think any harmonics from the coil will be a bit faint at this level anyhow; and even if they were powerful enough the rx would just slow down or stop, it would not get through to the servos. I think the problem is the rapid bumps on the ignition battery leads, caused by the ignition capacitor discharge, they are induced on the rx leads, by virtue of close proximity, and thus get through on the power leads. It seems that 2.4 receivers need no decoupling capacitors, these are basically there to prevent any voltages surges within the receiver; they also seem to need very few other components too, probably one of the reasons why they are small, light and cheap. Sometimes! I have seen one with a weight of 0.75 of a gram. My colleague is also into the Polaris, I did a thread somewhere and there are some photos in my album. He’s keen to try off water, I think that’s where they originally started. He started doing flat out touch and goes down the runway, and that has now developed into ducks and drakes. I’m sure he’s done three or maybe even four, but that will be very spectacular on water, we shall have to find a video camera. If nothing else, it may be YBF material! His model already has a fair bit of poke, he’s good with electrics, and I will not be at all surprised to find it’s been uprated a bit soon. He’s also had a few requests from the some other members too, he can build models like an assembly line!Good Luck.PB Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted January 19, 2012 Share Posted January 19, 2012 2.4Ghz Peter Edited By Tim Mackey on 19/01/2012 17:28:36 Quote Link to comment Share on other sites More sharing options...
Peter Beeney Posted January 19, 2012 Share Posted January 19, 2012 Yes, I did wonder if anyone would spot my deliberate mistake…… …or better still, I should perhaps re-read that like wot I just writt. My only excuse is that I can no longer resonate as fast as I could once upon a time… And what’s more or less only 2.3976 GHz between friends anyway… PB Quote Link to comment Share on other sites More sharing options...
Philflyer Posted January 1, 2021 Share Posted January 1, 2021 I have flown two NGH GT9s for 6 years now with considerable reliability and enjoyment. I also had the NGH 17cc that only lasted one flight due to radio failure. I thought the problem was a faulty lead connecting the Spektrum remote receiver but later through experience with the GT9s I found the most common fault was the Rcexl spark plug cap. It is easy to fit the cap badly as it is very stiff when new and loose when old. If this happens a spark occurs between the cap and the plug that causes loss of control with the DX6i, mostly at full throttle. The fault can disappear very quickly but may also cause a receiver brownout and disaster. Consequently I have been very careful when fitting the cap and always do a control check with the engine at full power as part of my pre flight checks. This morning, however, I had a rapid and intermittent elevator glitch when at full throttle in the air just after take off. I made a quick circuit and landed. For once the fault could be reproduced on the ground, only at full power, and I immediately suspected the plug cap. It was very dirty inside, old baked oil, so I cleaned and refitted it and all seemed ok. The next flight was similar however so I started packing up, to go home and investigate further. As I took the cover off the bottom of the fuselage to release the wings (a Seagull Cherokee) I noticed the Rcexl ignition unit had come loose from its velcro and one corner of the metal housing was touching the steel throttle cable. I attached the unit back in its place and tried again. Perfect! As luck would have it a few of us old and bold guys had been discussing radio problems due to metal to metal contact at the field a few days ago. I had heard of it of course and always use a nylon clevis at the carburettor but this took me by surprise. I am so glad I could reproduce the problem because had it not been found and a wreck had ensued it is extremely unlikely that the fault could have been found so probably blamed on other parts of the radio. A lesson well learned. Let’s hope the rest of 2021 continues as lucky! Quote Link to comment Share on other sites More sharing options...
Alan Gorham_ Posted January 1, 2021 Share Posted January 1, 2021 I'd be fascinated to learn how RFI at the plug cap can cause the receiver to brownout. Quote Link to comment Share on other sites More sharing options...
Philflyer Posted January 3, 2021 Share Posted January 3, 2021 It’s a guess. The spark interference causes servo movement that I assumed was from the receiver and it was swamping the transmitter signal. Do you have knowledge that might improve my guess? Edited By Philflyer on 03/01/2021 16:29:42 Quote Link to comment Share on other sites More sharing options...
Alan Gorham_ Posted January 3, 2021 Share Posted January 3, 2021 I think you are confusing saturation of the receiver by interference with an interruption in the power supply to the receiver that can cause the microcontroller to act unpredictably when the supply is restored. IE brownout has nothing to do with it. Quote Link to comment Share on other sites More sharing options...
Ron Gray Posted January 3, 2021 Share Posted January 3, 2021 I did a lot of testing on this problem a while back on FrSky gear CDI interference Quote Link to comment Share on other sites More sharing options...
Peter Christy Posted January 3, 2021 Share Posted January 3, 2021 Ignition interference can be quite strong, particularly to nearby receivers, so it is very important to ensure that plug leads and screening are all in good condition. In theory, ignition noise tails off above about 600 MHz - but it may find other ways of breaking into a receiver rather than coming through the aerial! Harking back to the 35 MHz days, some will remember clubs having issues with flying through microwave beams cutting across their fields. The beams in question were nowhere near 35 MHz, but were powerful enough to break directly into the audio and decoder circuitry. Wrapping the receiver in tin foil often provided a cure! Interference can also break in through the power lines. Some years ago, I had an issue with a piezo gyro causing glitching in a helicopter. Upon investigation, I discovered that the voltage booster inside it was putting several VOLTS of interference onto the battery supplies! I switched to another brand, and the problem went away! So yes, in theory 2.4 GHz should have better ignition noise immunity than lower frequencies. But ignition noise has a way of working its way in through unexpected paths, so take care! In particular, make sure all plug caps, HT leads and associated screening are in good condition! -- Pete Quote Link to comment Share on other sites More sharing options...
Philflyer Posted January 4, 2021 Share Posted January 4, 2021 Ok. So what is a brownout? Quote Link to comment Share on other sites More sharing options...
Peter Christy Posted January 4, 2021 Share Posted January 4, 2021 Brownout: Occurs when the voltage drops below the minimum required by the receiver. The receiver stops working! It may reconnect if/when the voltage recovers, but may take a few seconds, which can be disastrous. Usually the result of a combination of weak batteries and/or poor quality switches and high current servos. -- Pete Quote Link to comment Share on other sites More sharing options...
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