Radio system troubleshooting tips... Help it doesent work!

[Rpmtech1]

"I plugged it all in together, and it doesent do what it should! Now what?"

When you need to find the root of a radio system or electrical system problem, Take some logical and thourough steps to solving the problem and isolating the cause. have some patience and do it right.

Test the radio link:

1)
The first step should be to remove ALL connections to the receiver, and power up your transmitter and receiver and verify a good radio link. Power the receiver from a separate source other than the models BEC. If you dont have a separate source, get one! A 4 cell rechargable battery pack can be had for next to nothing and is a valuable tool for RC modeling. You can even tape together 4 AA batteries and make an ad hoc pack if your in a pinch.

2)
Plug a servo into all channels, one at a time and verify that all channels are working and the servos are moving when you manipulate the corresponding controls on the transmitter. If none of them are working at all, verify you have actually powered up the receiver with a good source. With a powered up receiver and transmitter, every time you plug a servo in, it should move a tiny bit and make some noise for a second. Quick indicator of a powered up system.

3)
If still nothing, check the radio crystal in the Receiver and be sure the channel on it matches the channel on your transmitter. If you have bought a second hand radio, sometimes the previous owner could have swapped out the crystal in the transmitter to a different channel one. Physically take it out and look at it, it should have a tab on it with a 2 digit number, this is your "channel". Both transmitter and receiver need to have the exact same number, 2 digit channel.

4)
Be certain that your transmitter is set to the correct modulation. This will usually be "PPM" or "FM". The other modulation option is PCM. If your receiver says PCM on it, then be sure to change the transmitter to this. I have scratched my head and paced around cursing a few times because I dident have the modulation set right!

5)
If you are certain that its powered up, and both transmitter and receiver are on the same frequency's, same modulation type "PPM" or "PCM" but its still not working, you have isolated it down to a radio link problem. If you have another receiver, test it out with the transmitter same as above, to be sure its not the transmitter before you toss the thing in the garbage!

Receivers very rarely fail unless abused by water or short circuiting. One drop of water on the receiver board and it will most likely act strange and/or go nuts! So be sure that the thing is 100% dry.

[Rpmtech1]

More to be added soon!

[greenman407]

Very Useful to say the least. Ive been in that situation more times than I care to relate. The best thing that I ever did was buy a Polk. Havent had any problems since, not even with their recievers.

[He Who Shall Not Be Named]

I agree with you there, Mark: The Polk r/c system is very, very good. Love the transmitter -- but that instruction manual is simply maddening!

And the receiver is almost as good as the Sombra receivers -- and that's high praise indeed!

I have two of the track-3 transmitters and love them to death.

David,

[Rpmtech1]

Next: BEC's and receiver power

Your ESC has a built in BEC (Battery Eliminator Circuit) that will take power from the drive battery, process it and feed the receiver and servos. The problem is that almost all built in BEC's can only handle maybe 2 loaded servos at most.

Whats really needed is an external BEC for most boats with more than say 2 micro servos. Without one when you pull manuevers and load multiple servos up, you are at risk of "browning out" the power due to the overworked BEC and the receiver could loose its link with the transmitter. All sorts of strange behavior can be had with a maxed out BEC. Nowday External BEC's can be had for very cheap, Turnigy brand ETC.


When installing the external BEC, Remove the red wire from the ESC connector going into the receiver. If you dont, the receiver internal BEC and the newly added external BEC could fight each other, and one will loose and cook. Most likely the ESC.

ALSO: set your servo end points so that the poor things are not fully stalled at the extreme ends of their travel. This is called on most radios "ATV". If you dont have a radio with ATV adjust, get one, your in the stone age.

[Slats]

Your ESC has a built in BEC (Battery Eliminator Circuit) that will take power from the drive battery, process it and feed the receiver and servos. The problem is that almost all built in BEC's can only handle maybe 2 loaded servos at most.

Whats really needed is an external BEC for most boats with more than say 2 micro servos. Without one when you pull manuevers and load multiple servos up, you are at risk of "browning out" the power due to the overworked BEC and the receiver could loose its link with the transmitter. All sorts of strange behavior can be had with a maxed out BEC. Nowday External BEC's can be had for very cheap, Turnigy brand ETC.


When installing the external BEC, Remove the red wire from the ESC connector going into the receiver. If you dont, the receiver internal BEC and the newly added external BEC could fight each other, and one will loose and cook. Most likely the ESC.

ALSO: set your servo end points so that the poor things are not fully stalled at the extreme ends of their travel. This is called on most radios "ATV". If you dont have a radio with ATV adjust, get one, your in the stone age.

Thanks Rick for championing this point - the root cause of many electrical glitches I and others have experienced relates to the use of the modern compact ESCs that come standard these days with an in built BEC.

What most don't realise is the on board BEC is linear and has reduced capacity with higher voltage inputs. For example the BEC might be stated on a manufacturers ESC to be 1AMP, the ESC might be rated for example to take 6-12v input voltage. The BEC's advertised 1AMP capacity however is not 1AMP across the whole range of input voltages. A good rule of thumb is the advertised BEC amp capacity should be taken at the lowest input voltage -in this example at 6V. You then say double the battery input voltage to 12V and you then HALVE the BEC amperage capacity down to 500mA.

I have extensively tested the current draw of all my gear that hangs of the RX. Whilst servos typically under no load draw around 30-50mA, they can easy chuck out close to 3 amps a pop BEFORE stalling. Restricting the servos throw from extreme points is a good idea, but the measured load through the water tight glands still sees a well set up boat punch up close to 1amp out of the water with push rods moving through water tight glands and / or o'rings. - Don't believe this? - go over to a site like Tower Hobbies and read there constant little disclaimer for most servos "This servo can produce high-current draw from your batteries"

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXH288&P=ML

I have been in the sub game long enough to see a very big shift in electrical reliability problems. The shift in reliability is associated I believe with the miniaturisation of RC equipment allowing smaller subs to occupy a practical space in the market place and in my experience is almost completely related to the take up of smaller some times waterproof ESCs being relied upon to power the magic 5v rail to the RX.

Best
J

[KevinMc]

This is a great thread Rick, thanks for taking it on.

ALSO: set your servo end points so that the poor things are not fully stalled at the extreme ends of their travel. This is called on most radios "ATV". If you dont have a radio with ATV adjust, get one, your in the stone age.

I'd go so far as to say that they shouldn't be stalled at all. A good friend of mine spent an entire season fighting with "gremlins" in his sub for this very reason. ATV's are an easy thing to overlook, but it's critical that this step is performed. Don't have ATV's in your radio? This is no excuse not to check! Pull the control rod in by one hole on the servo arm if it stalls out at the end of travel. This step cannot be overlooked or sooner or later you're going to pay for it! (My friend went through several ESCs and external BECs because the overload would cause things to catastrophically fail - not to mention the frustration of having his boat routinely go dead in the middle of the pond!)

[Kazzer]

This is a great thread Rick, thanks for taking it on.



I'd go so far as to say that they shouldn't be stalled at all. A good friend of mine spent an entire season fighting with "gremlins" in his sub for this very reason. ATV's are an easy thing to overlook, but it's critical that this step is performed. Don't have ATV's in your radio?

Kevin


Do the Wfly radios have this feature? Could you give us instructions for the 6 ch and 8 ch transmitters please?

[Slats]

If your radio doesn't have it don't sweat it. Subs have been around a heck of a lot longer than the computer jobs that all have these.
Get the mechanical setup right - look at the position of the z bend on the horn holes, bend the the push rods to accommodate the smoothest route through the push rods from the horns. All that said if you have the function on your radio use that too!!

[Rpmtech1]

Mike,

Almost all radios now have that feature, save for the super ultra cheap ones. The Wfly 6 has ATV from the looks of it, and im sure the 8 does

[Rpmtech1]

John,

I just recently built a Tamiya car and it came with an ESC. Steering would go wild every time I gave it gas! I knew it was not my 2.4 radio. Put a external BEC in there and problem solved.

So yeah they can cause problems for sure!

[KevinMc]

Kevin


Do the Wfly radios have this feature? Could you give us instructions for the 6 ch and 8 ch transmitters please?

I believe the W-FLY6 does not have ATVs, the W-FLY8 most certainly does. Irrespective of having ATVs or not my setup procedure is always the same - (as John suggests) get it as good as you possibly can mechanically, and only then do you look at trimming it up electronically where available.

[Rpmtech1]

It says "travel adjust" for the 6 channel... dont know much about these radios though

http://www.caswellplating.com/models/transmitter.html

[KevinMc]

Confirmed - no ATVs on W-FLY6. (There is a dual rate switch that forces channels 1,2,4 and 6 to simultaneously travel over a +/-125% range instead of +/-100% range, but I wouldn't call that an "ATV" in the sense we're discussing.)

[Slats]

John,

I just recently built a Tamiya car and it came with an ESC. Steering would go wild every time I gave it gas! I knew it was not my 2.4 radio. Put a external BEC in there and problem solved.

So yeah they can cause problems for sure!

Its a problem I am seeing more and more of Rick.

With subs back a decade ago, everyone here ran boats with separate Voltage regulators, as not that many BECs were coupled to ESCs. The problems we had and worked to resolve were predominantly mechanical in nature, such as avoiding leaks! There has been a real shift in my experience to the dominant problems being nowadays electrical.

What changed?

Simple answer, the electronics got smaller and more packed with features. Finding an ESC now that does not have an on board BEC is not impossible, but they are fewer in number. Most come with the BEC and most people I know who are brand new to the hobby would not give it a second thought that the BEC might not be up to the job in a sub. Even experienced sub drivers too can fall into the trap of now thinking great I no longer need a separate voltage regulator. I was initially in this category of thinking the ONLY reason why I had used a separate Voltage Reg previously was that the ESCs back then didn't have them. Now wiser I rarely have electrical problems and I always either use a separate voltage regulator / BEC.