Model Boat Mayhem
Technical, Techniques, Hints, and Tips => Radio Equipment => Topic started by: Pvtspoon on March 23, 2015, 01:05:11 pm
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has anyone had any interference with 2.4Ghz as the weekend just gone when down at the local pool we had 3 boats that was running fine sluddenly fly off at full throttle with no control all off the Tx & Rx where of diffrent makes. what interferers with a 2.4Ghz signal that makes the Rx think you want full throttle
Thanks in advance
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Some of the cheaper 2.4g sets default to full ahead on loss of signal
Maybe a range issue.
Ned
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defo not range the pools only 147m long & 74m wide, 2.4 was spectrum, planet, & some odd german make
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Hi,
A lot of mobile devices use the 2.4Ghz band, everything with Bluetooth and WiFi , laptops, tablets etc.
Just some suggestions...............
Was someone using a device for taking photos or trying inadvertently to connect to a WiFi?
European transmitters are limited to 10mw - was there a local device transmitting on higher power and causing loss of signal?
Were the transmitters/receivers set for minimum throttle on loss of signal, but the servos/ESC not set up in the correct direction?
Ian.
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You say the Tx and the Rx were different makes? Could this not be the cause? I understand that to bind themselves they have to be of the same make?
Mick F
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If I had to bet I would say that someone nearby had a phone that was transmitting as a wireless hotspot.
Lots of phones, and data plans, now allow for people to "tether" their devices to a mobile phone, thus making the phone a hotspot.
Although they shouldn't interfere it could be possible that a phone left in this mode, that had perhaps had a knock to the area where the antenna is inside the phone, could have caused interference.
A friend of mine bought a cheap RC aircraft that came ready to fly. We tried to test it out but the TX wouldn't work at all. After some digging around with a wireless analyser app on one of our phones is turned out there was a strong signal coming from his mobile phone set as a hotspot. His phone was an iPhone and with him being an electrician it got bashed about a bit and was all smashed up.
When he turned it off the aircraft flew fine, with it on the TX was entirely useless.
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You say the Tx and the Rx were different makes? Could this not be the cause? I understand that to bind themselves they have to be of the same make?
Mick F
Tx and the Rx where not different makes Tx & Rx same make but three diffrent makes had the same interference issue
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I donīt believe it was interference with other systems.
The data are transmitted digitally, not analogue as in the good old 40mHz times. So if a data package is corrupted due to interference itīs just ignored. It seems absolutely impossible to me, to "create" a "full throttle data package with all other channel informations correctly" with a telephone.
95% of those "loss of connection" are caused by bad reciever power supply, brownout of the reciever and badly set up of failsave.
btw @rottweiler. Nice nickname, I would have chosen it by myself, since Iīm a true Rottweiler O0 (born in the city Rottweil).
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You may not be able to mimic the full throttle packet it but its entirely possible to swamp the signal, forcing it to go into failsafe. If this was then not setup correctly you could see the issue the OP suggests
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I donīt believe it was interference with other systems.
The data are transmitted digitally, not analogue as in the good old 40mHz times. So if a data package is corrupted due to interference itīs just ignored.
thats what i was thinking comming from an I.T background
bad reciever power supply, brownout of the reciever and badly set up of failsave
failsave set up right as tested it again tonight on over half throttle and turn Tx off yep boat turns off, Rx not popped, bad reciever power supply ESC has BEC on board
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Did you have all three for test or just one.
Something is swamping the receivers.
No new phone masts popped up in the area?
Ned
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Did you have all three for test or just one.
Something is swamping the receivers.
No new phone masts popped up in the area?
Ned
the other two boats arnt mine other members boats
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I still cant believe that you can "improvise" a full throttle package with a mobile or mast or different 2,4 Ghz radios.
This seems absoutely impossible due to the complexity of the transmitted data and the fact that a data package is sent just over a fraction of a ms and with a unique ID.
If the Rx recieves data packages which are just slightly corrupted it will ignore them and after some time go into failsave mode.
The only inteference I know, is with the cheap orange TX modules, where 2 TX can interfere to each other due to a software bug (same ID on several TX modules possible).
If the failsave is setup correctly I have no answer to it. It seems impossible from the point of the radio.
Maybe it was the ESC by itself, some program error or whatever.
By the way, most BEC are so crappy (and highly overrated regarding amps) that this is unsufficient receiver power supply even with just 1 digital servo.
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Not sure about this, but I do know that mobile phones have been used to hack bluetooth devices (e.g. http://www.japantoday.com/category/technology/view/high-tech-toilets-vulnerable-to-hacking).
I am not sure if this also applies to 2.4Gig
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It really doesn't matter how complex the transmitted signal is, if it gets swamped by a larger one, the RX regards it as a "lost" signal, and responds accordingly. In all probability, the more complex the signal, the more liable it is to corruption. Complex handling of the signal allows for a proportion of frames to be lost without any noticeable effect, but exceed that number, and the RX, if so fitted, will go into its alleged failsafe mode. Failsafe is usually "stick full back", which, for the majority of the market (planes) is "off", which causes them to come down. For boats, it usually results in full reverse, which is never a good thing. On old type radios, loss of signal just meant a loss of output to whatever was plugged in, modern, so-called "clever" receivers are quite capable of having a response built in that keeps an output going. There probably isn't a way to reprogram the RX, only the TX, which doesn't help.
While 2.4GHz is immune to the more conventional forms of interference, being way, way, out of band of the regular sources of interference, with all of the other devices now using the band, low power model control can be swamped and/or crowded out. Loss of range would be the first symptom, since the signal strength that the receiver gets from its bound TX reduces with range, and there will come a point when the unwanted signal from the interfering source is strong enough to swamp enough information frames.
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Here is a question.
Could someone using a drone with 2.4g video link do this?
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Here is a question.
Could someone using a drone with 2.4g video link do this?
Logic says no - the drone is being controlled via 2.4. But with interference problems, the answer is often only logical after you know the answer.
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Logic says no - the drone is being controlled via 2.4. But with interference problems, the answer is often only logical after you know the answer.
DJI Phantoms use a 2.4GHz video signal to link with a phone over WiFi and are controlled with a 5.8GHz transmitter. Video signals tend to be very wide band and cover several of the channels used by our transmitters and are known to cause problems. Some of the older 2.4GHz sets (eg. Spectrum DSM and DSM2) do not do proper frequency hopping and can be swamped by a video signal covering the channels they use. (DSM and DSM2 only use 2 channels which they can move between.) Proper channel hopping radios which cover the whole frequency band should be much less susceptible to swamping unless the interfering signal is also covering the whole band.
The failsafe throttle position on most Spectrum receivers is set at binding so make sure that the throttle stick is set to the off position when binding the set.
Jim
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Hi,
A lot of this thread was covered recently in http://www.modelboatmayhem.co.uk/forum/index.php/topic,50002.0.html , particularly a more detailed description of the Spread Spectrum techniques that our systems use.
My Futaba R617FS receiver maintains it PWM outputs despite the transmitter being switched off. The channel 3 (throttle) is programmable to revert to minimum on loss of transmitter signal.
At the moment this feature is a nuisance for my boat's Voice Command System that I'm building, since it prefers to see total loss of PWM from the receiver so that it can fail safe.
With the current Futaba receiver still pumping out PWM signals even with the transmitter off, I've got to come up with a different solution for fail safe.
Ian
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thats what i was thinking comming from an I.T background
failsave set up right as tested it again tonight on over half throttle and turn Tx off yep boat turns off, Rx not popped, bad reciever power supply ESC has BEC on board
I had a similar problem, changed speed controllers,still the same,died when past half throttle,
Changed the motors,still the same,so to the test tank,wattsup meter in circuit,7.2 fully charged
Showing 8 v started the motors keeping an eye on the meter,all o/k voltage ok,
Moved stick from neutral to half stick the voltage went down to 4.2v the Rx shut down.
Tried a different. Battery and it ran with no problems.
Proving that the batteries 2off in my case had faulty cells.(I mean 2batteries can,t be faulty)?
So I had changed esc,s, , motors when it was faulty batteries that failed under load.
John
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A common problem with three totally different models all on 2g4
certainly sounds like swamping from a wideband transmission
covering the whole spectrum if the radios are fhss or dsmx.
We had the opposite problem with a 2g4 camera link on a tug.
All that could be seen on the monitor was soundbars as soon
as a Planet Tx was flashed up.
Ned
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Hi,
My Futaba R617FS receiver maintains it PWM outputs despite the transmitter being switched off. The channel 3 (throttle) is programmable to revert to minimum on loss of transmitter signal.
At the moment this feature is a nuisance for my boat's Voice Command System that I'm building, since it prefers to see total loss of PWM from the receiver so that it can fail safe.
With the current Futaba receiver still pumping out PWM signals even with the transmitter off, I've got to come up with a different solution for fail safe.
Ian
Ian does your transmitter have the ability to set the maximum movement for the channel? If so set up your failsafe to give more than normal movement for the throttle channel and set your software to look for this. I use this on a turbine powered jet to cut the engine on failsafe without affecting normal control.
Jim
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Hi Pvtspoon,
I'm intrigued by your report of interference on 2.4Ghz. I'm the pool master and/or frequency control officer at a number of major RC events where very high numbers of 2.4Ghz sets (of various makes) are in use. At one particular location there are also multiple wi-fi services in operation as well. We have never experienced any problems.
I suspect that someone was using a high powered broad band piece of 2.4Ghz equipment in the vicinity (possibly deliberately) and this completely swamped all the receivers. If only one model had a problem then there could be a variety of reasons for this BUT you state that all 3 models had the problem at the same time. Unfortunately it is possible to purchase on the open market transmission devices that put out several Watts of power as opposed to the mili-watts (mW) that our TX's put out. It is not illegal to sell or buy these devices BUT it is illegal to use them - although the chances of being caught are less than zero.
There is every chance that your models were the target of an idiot doing what idiots do!
If it continues to happen keep us informed as it is possible to monitor the radio spectrum and see whats going on and to trace the source.
Steve Dean.
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Does anyone know the pep of video downlinks and bandwidth from these
Toys?
We see a few of them overflying our lake.
Operators are not in sight as we have banks around
the lake so where they are we do not know.
Ned
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The video downlinks from quadcopters and other multi-rotor 'Drone' type aircraft are on either 2.4Ghz or 5.8Ghz. The ones on 2.4Ghz should not interfere with other models as otherwise they would be capable of interfering with themselves. The units that use 5.8Ghz are obviously on a much higher frequency and therefore will not interfere with models on 2.4Ghz.
Regarding the transmit power of these devices there is a legal permitted level, however units are available from retailers and the internet that far exceed these levels by a very large amount. As I have already pointed it is not illegal the sell or purchase these devices
.. the offence is to use them (in this country).
It is possible to use TX/RX's that use 5.8Ghz to control the model and use a high power 2.4Ghz device for the video downlink. If the 2.4ghz device is a low cost broadband transmitter then it would produce radio frequency power across the whole of the 2.4Ghz band. In relatively close proximity this could in effect wipe out the 2.4Ghz band.
To put this in context many retailers sell models complete with 27Mhz transmitter for very low prices and these are not crystal controlled. I once tested one of these and its RF output splattered from 26Mhz all the way up to mid 28Mhz !!!!
There is no real answer to this situation other than to be vigilant if other models are operating nearby. If you suspect you are sustaining interference from other models then it is worth investigating what they are using and why it is causing you a problem.
A note of warning to people who are new to the hobby
.. we all know it is possible to buy extremely cheap equipment, however some of the dirt cheap transmitters put out very low power and in essence they work ok. BUT if your model is at range and sails very close to a higher power transmitter (or several) then the RX may be swamped by the close by transmitter.
Steve Dean.
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It really doesn't matter how complex the transmitted signal is, if it gets swamped by a larger one, the RX regards it as a "lost" signal, and responds accordingly. In all probability, the more complex the signal, the more liable it is to corruption. Complex handling of the signal allows for a proportion of frames to be lost without any noticeable effect, but exceed that number, and the RX, if so fitted, will go into its alleged failsafe mode. Failsafe is usually "stick full back", which, for the majority of the market (planes) is "off", which causes them to come down. For boats, it usually results in full reverse, which is never a good thing. On old type radios, loss of signal just meant a loss of output to whatever was plugged in, modern, so-called "clever" receivers are quite capable of having a response built in that keeps an output going. There probably isn't a way to reprogram the RX, only the TX, which doesn't help.
While 2.4GHz is immune to the more conventional forms of interference, being way, way, out of band of the regular sources of interference, with all of the other devices now using the band, low power model control can be swamped and/or crowded out. Loss of range would be the first symptom, since the signal strength that the receiver gets from its bound TX reduces with range, and there will come a point when the unwanted signal from the interfering source is strong enough to swamp enough information frames.
Absolutely agreed.
But, the thread starter stated that failsave was set correctly during binding, so there is no possibility the ESC goes full throttle just by swamping the signal.
So something is wrong here, or we might consider that we have to rething our common understanding of "logic".
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Probably a red herring! If the fail safe normally results in throttle full back which in a boats case would be full reverse what would happen if the throttle radio channel setup had been setup with servos "reversed"! Would this result in full throttle?
Jonathan
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Probably a red herring! If the fail safe normally results in throttle full back which in a boats case would be full reverse what would happen if the throttle radio channel setup had been setup with servos "reversed"! Would this result in full throttle?
Jonathan
With so many programmable links, red herrings are very possible. You can tell the TX how to respond, in some cases it might well be possible to tell the RX how to respond to a loss of signal. Many ESCs have a programmable feature. All of these are potential pitfalls, especially when you consider the possible permutations.
Channel reverse plus motor wiring reverse giving a "failsafe full forward"? Probably, maybe. I have some cheap ESCs that have an asymmetrical F/R and are designed around Futabas thinking. To get full forward and a calm reverse I have to do the reversing everything trick. Other ESCs with relay reversing are bad news if they need to be run "reversed". The relay puts a large drain on the radio power supply when operated for actual forward.