Sailboat electronics cutting out while running after changing servos

[Edward Hobbs 2Participant @edwardhobbs2]

Hi Folks,

I'm experiencing a very frustrating issue with my Footy RC boat. I had originally set the boat up with two 9g servos – one for the rudder, one for the sheeting arm. This was using the "power arm" setup to give the 9g a fighting chance, and worked okay – it had some issues in stronger winds though so I wanted to update to a larger sail arm.

I replaced the 9g servo with an MG995 servo as it's capable of around twice the power, but whenever I try and sail with it my electronics will randomly cut out. Sometimes they will come back after i move the sticks a bit, sometimes they will die for good and i have to wait for the craft to drift back to shore.

I thought it may be a case of the servo drawing too much power in high winds (our local lake is VERY windy!) however the exact same problem happened this thursday when there was very little wind at all.

I thought it could be the fact that I'm using rechargeable batteries that are only rated at 1.2v and the receiver takes between 4.8-6v, 4 full batteries is ~5.5v. I tried 5 batteries in case the extra power would help and the receiver exploded so that's definitely not the solution!

I'm currently in the process of converting back to the 9g setup to rule out anything else, but given the only thing that changed was the servo I think it may be the culprit.

Have any of you ever seen this sort of behaviour and managed to fix it? Is it a case of cheap servos causing the receiver to fail? Any help would be most appreciated.

Thanks,
Ed

[Edward Hobbs 2Participant @edwardhobbs2]

[Richard SimpsonParticipant @richardsimpson88330]

Firstly welcome to the forum. Just a couple of thoughts, firstly you said "…and the receiver exploded…" which I assume is not strictly what happened?

There are a couple of things that could happen with putting a new bigger servo in, one is are you sure that the servo arm is not interfering with any part of the model? Then the next thing to check is that you have enough slack in the sail cord to allow the movement of the servo arm. If there is not enough slack the servo will be over loaded. Check that the movement of the arm is the same with the cord connected and disconnected. Does the servo make any unusual noises as it operates?

As regards the batteries you do need to be sure they are fully charged or fresh so you will be supplying 4.8V with four rechargeables or 6V with four non rechargeables. That's why the receiver is designed to operate within that range.

If possible try a few different servos in the same set up and test them all. There is a possibility that a brand new servo might have a fault so you need to eliminate that. I have only just received a brand new speed controller, which simply doesn't work and is going back, so it happens.

[John W EParticipant @johnwe]

hi there

I had a quick look on line about the specs of this servo you are using – and – my first thoughts are – Is it a digital servo that you are using? on an analogue set?

If it was this – it could cause some of the problems.

But, if you read through some of the comments on the link I have put on (if it works) – that some people don't rate these servos very well and there seems to be a problem with them.

The other thing I notices is that in the advert for them they are a 180 degree turn servo – or – you can have a 360 degree turn servo.

**LINK**

John

[geconParticipant @gecon]

Hi Edward, I am not an expert….but my thoughts are;

Most servos are produced to operate on 4.8v. A few accept up to max 6v. but they don't usually 'like' 6v. 5 X1.2v -fully charged cells deliver more than 6v for a while. This may cause damage to the circuitry.

I think the long 'power arm' on a small servo may overload it somewhat. Does it come with a long arm? or did you make it yourself? A long arm gives more sheet movement, but needs more battery capacity to move it -especially in a breeze!

Ray Wood 2 is a 'power arm' fan, maybe he can give some info?

The anologue/digital compatibility issue may also be a factor as John mentions. Digital servos require more battery capacity too… ie amps, not volts.

There may be a voltage drop in your setup which causes the whole show to shut down. ie. voltage drops to below 3.6v when sailing.

George

 

 

Edited By gecon on 20/06/2022 08:00:30

[Edward Hobbs 3Participant @edwardhobbs3]

Hi All,

Thanks for the replies, sorry about the late response I'd got distracted by other things…

I wasn't exaggerating when I said exploded, i'm not sure what component specifically went but it did go with a bang, sparks smoke the whole 9 yards!

Since making this post i have finished rebuilding the boat with two 9g servos, and the same issue is still happening which is really very odd.

I'm not sure about the digital/analogue problem, it would make sense but I think the receiver uses the standard PWM signals so all should work fine? The 9g servos work fine on-shore then produce the same issue.

I should say that prior to trying with the larger servo the boat would sail absolutely beautifully, I spent a good 2-3 hours down at the lake pootling around with it and I only had to stop due to low transmitter power. I think my next port of call is to check if the transmitter is the one causing the issues? It's the only thing left to change as i've already tried:

– new receiver
– new batteries
– new servos both rudder and sail arm as the rudder servo also stopped working recently (but i think that's my fault for not waterproofing them at all)

[Edward Hobbs 3Participant @edwardhobbs3]

The only other thing I think it could be is that previously, i was using 4xAAs for power but currently i am using 4xAAAs. I wouldn't expect that to cause issues especially with such small servos but maybe they aren't providing enough power?

[Chris FellowsParticipant @chrisfellows72943]

Hi Ed

Pity you didn't mention that earlier!!!

And remember that old adage about only changing one thing at a time!

Anyway, that is more than likely where the problem lies. I can't think of anything else that I use other than tv remotes etc. that use AAA batteries and their power requirements are very low.

Why did you change to AAA? I suggest returning to AA and the original servos and if they work fine, then try the more powerful servo.

Chris

[Ray Wood 3Participant @raywood3]

Hi Ed,

I'm afraid the size of the cells AAA or AA has nothing to do with your problems, receivers are happy with voltage between 4.8v & 6v actually most racers are using 5 cell packs to give the winch or servo a bit more umph !!

I fly with AAA 300mah on lightweight aeroplanes no problem.

With the cost of radio sets at £35 for a drycell set, throw your old set away

Regards Ray

[Richard SimpsonParticipant @richardsimpson88330]

While the capacity can be limited on an AAA cell due to its physical size the important thing here is voltage and they are the same for AAA and AA, i.e. 1.2v for a rechargeable cell and 1.5v for a non rechargeable cell. The only thing you should notice is that the AAA set usually won't last as long.

I must admit I have never heard of a receiver going bang, something must have seriously gone wrong such as a huge over voltage or a failed internal component.

You haven't mentioned the radio or what you changed the failed receiver for but I'm going to suggest a complete clearing of the decks here. I have only just bought a radio set to operate a little tug boat for my great nephew, which was great value with a six channel 2.4G transmitter and included matched receiver for the grand sum of £40.00. Although the instructions do not tell you how you can convert the sticks to sail use.

Radio Link

I would buy one of those, get yourself a normal AA receiver pack holder and try it. I can't imagine your problems not being resolved.

[Chris FellowsParticipant @chrisfellows72943]

I stand corrected!

I was assuming, always a dangerous thing, that the lower capacity of the AAAs would soon be overcome by the work the sail servo was having to do, especially as it was working fine on the shore.

Chris

[Edward Hobbs 3Participant @edwardhobbs3]

No worries Chris – happens to the best of us! I had also thought that it could be a factor but I'm glad to be corrected on that front as it means I don't need to buy even more batteries! 😀

Richard –

The receiver that I have is a Flysky FS-R6B paired with an FS-T4B transmitter. I replaced the receiver like-for-like as it had been working fine previously and I figured that if it worked before it should work again. The one that exploded had just been fed probably 7v if my guesstimations are correct, which explains the rapid self-disassembly experienced. I had been considering upgrading to a nicer transmitter as I have several other models in the works and it'd be nice if i didn't have to re-pair for every one so I may take the plunge now – or at least on tuesday when i get paid!

Ray –

Thanks for confirming that the battery capacity is not the issue, forgive my ignorance but I'm not sure what you mean by a "drycell set" or what I should be throwing away exactly, please could you elaborate as I'm very new to the hobby and don't have a lot of experience just yet.

Thanks again everyone for the help, it's very gratefully received as this problem has been driving me up the wall…

[Ray Wood 3Participant @raywood3]

Hi Ed,

The term drycell set refers to being able to load the transmitter with individual battery cells, rather than the more expensive set which come with built in batteries and a charger, I thought with unpredictable faults throw the transmitter & receiver away, the FS-T4B is an old design running on 12 volts 8 X AA cells ?

As Richard & I said radio is very cheap these days.

Good Luck

Ray

[Edward Hobbs 3Participant @edwardhobbs3]

Hi Ray,

Yes that's correct it takes individual AA batteries – I bought it originally as it was one of the cheapest possible options that was still "proper" but it looks as though a trip to the hobby shop is in order!

Thanks for the clarification, I will update this thread with more news when I have "receive" (fnar fnar…) the new transmitter!

Thanks again,
Ed

[Edward Hobbs 3Participant @edwardhobbs3]

Slightly sooner than expected update:

I've been looking at radio sets and frankly I'm now more confused than before. I cannot find a single radio set that actually has integrated batteries and charging – every one, including that recommended by Richard is powered by replaceable AA cells. I think i'm missing some key information here, is there a difference between those sets that use 4xAAs vs those that use 8x?

I don't feel confident now purchasing anything if I'm going to run into the same problems I already have…

[Chris FellowsParticipant @chrisfellows72943]

Hi Ed

One thing to know when buying another transmitter/Tx (and hopefully my esteemed forumites concur with this) is that you don't need a Tx with a memory for a number of different models when you add to the fleet as the receiver/Rx can be bound with each.

That assumes that each model is basically the same and just needs throttle and rudder. Tx with memory for multiple models tend to be more complicated (and designed primarily for aircraft) and are useful for different sorts of models e.g. power and yachts, as the parameters for different things can be set and saved for each model.

Many of us to have more than one Tx and you could get 2 or 3 basic Tx, which is all you need for most boats, for the cost of one for multiple models.

Chris

[Chris FellowsParticipant @chrisfellows72943]

Hi Ed – our posts overlapped. I think it tends to be the more expensive "computerised" Tx I mentioned that have a rechargeable battery as standard though someone may be able to suggest one that does.

Nothing wrong with the Tx using AA cells. I have a Tx with them and the batteries last all year! Be wary of replacing the AA with rechargeable AA though as the voltage can be too low as 1.2v per cell rather than 1.5v.

Chris

[Edward Hobbs 3Participant @edwardhobbs3]

Thanks Chris that makes sense,

I'll go for the transmitter that Richard suggested and get some non-rechargeable batteries to power it. If it still misbehaves after that… well I'll not worry about that for now

Best,
Ed

[Chris FellowsParticipant @chrisfellows72943]

I don't know if that one can be bound with multiple Rx? Many can but not all. Though you might not be worried about that at the moment?

Chris

[Richard SimpsonParticipant @richardsimpson88330]

Edward, as Chris says the rechargeable ones tend to be the more expensive sets, although the only real advantages are that you do not need to keep purchasing new batteries. Non rechargeable sets work perfectly well and the one I suggested has a battery level indicator so when they get low you know its time to change them.

I use a relatively expensive Spektrum set with non rechargeable batteries and never had a challenge with it. Fully agree with Chris though, if the transmitter is designed to use non rechargeable batteries then do not fit rechargeable batteries. Just keep a spare set of Duracells in your tool box!

[Edward Hobbs 3Participant @edwardhobbs3]

Not hugely worried about that at the moment – long way to go before other models will be ready and the receiver on the suggested set is a lot easier to pair than the flysky version (jumper cable over the power input, unplug all the servos, plug the batteries in somewhere else) so at the very least I should be able to buy more receivers and swap between with reasonable speed.

I think that's the better solution right now, as I can then save for a more capable set further down the line when it would be more convenient

[Edward Hobbs 3Participant @edwardhobbs3]

Thanks Richard that's great advice, I hadn't realised rechargeables were such a pain or I'd not have bothered in the first place!

[Edward Hobbs 3Participant @edwardhobbs3]

Update:

The new radio set arrived on Tuesday, after a couple of false starts with wind dropping off the second I arrived I've managed to get 1-2 hours sailing in and everything appears to be working perfectly again.

I did discover that the new receiver has some different behaviour when low on battery compared to the previous set, it still listens to inputs but mostly jitters around – thankfully i had my tennis-ball-on-a-string at hand to rescue it.

Thanks everyone for all the useful advice, It looks as though replacing the radio was the answer in the end. It is now tempting to try it again with the larger servo but I think that may be tempting fate and i should leave it as it is since it's working!

[Richard SimpsonParticipant @richardsimpson88330]

Good news Edward, glad things are working again.

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