John Laverick Posted April 16, 2017 Share Posted April 16, 2017 Hi guys, a quick problem that's driving me nuts. When I operate the retracts on my plane the flap servos go wild!!! I also have a reaction when I operate the elevator ( albeit very minor compared to the flap) the flap servos have a servo reverser on them. I've tried putting the flaps on aux channels with no joy! Any help appreciated John Edited By Chris Bott - Moderator on 17/04/2017 10:06:25 Quote Link to comment Share on other sites More sharing options...
will -0 Posted April 16, 2017 Share Posted April 16, 2017 You have to try unplugging/bypassing things one at a time until the problem goes away. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted April 16, 2017 Share Posted April 16, 2017 Do you have a separate retract battery (I assume they're electric, not pneumatic?) . If not, the load from the retracts might be dropping the supply voltage to the other servos unacceptably...although I'm not sure what your elevator reaction is affecting/being affected by from your description. Have you tried connecting the servos direct to the receiver? Could be a dodgy extension lead... Could we have some more details? Radio type, power supply, servo types involved etc? Quote Link to comment Share on other sites More sharing options...
John Laverick Posted April 16, 2017 Author Share Posted April 16, 2017 I've just had a play with it again Martin, seems to be two different reactions. When I operate the retracts the flaps actuate wildly, when I put operate the elevator the flaps move in conjugation with the elevator, both up and down. I'm using a Turnigy ia10 Rx an Tx. However I must add I've at present I'm using a 4.8v plug in power source. I've not tried it with the flight batteries. Perhaps the draw from the retracts is affecting the flaps? Although it doesn't explain the flap elavator reaction! Quote Link to comment Share on other sites More sharing options...
John Laverick Posted April 16, 2017 Author Share Posted April 16, 2017 I'll have a try with the flight batteries and report back Cheers John Quote Link to comment Share on other sites More sharing options...
ChrisB Posted April 16, 2017 Share Posted April 16, 2017 Have you got any odd TX channel mix or landing mode type settings set in the TX? If 6v doesn't cure it and you can't find the error then i'd reset the model memory. Quote Link to comment Share on other sites More sharing options...
John Laverick Posted April 16, 2017 Author Share Posted April 16, 2017 I'm on the case with the flight battery Chris, I did think perhaps I'd managed to do summit like that, cos it looks as if the flaps are mixed with the elevator? I might have done it by mistake, that's a good suggestion 👍 Quote Link to comment Share on other sites More sharing options...
John Laverick Posted April 16, 2017 Author Share Posted April 16, 2017 Interesting? I've plugged the flight batteries in, connected only the flaps and gear servos, but when I put in elevator movement the flaps move as though they were the elevator!! Does that suggest there mixed? And no I've not plugged the flaps into ch 2🤔 Quote Link to comment Share on other sites More sharing options...
John Laverick Posted April 16, 2017 Author Share Posted April 16, 2017 Still went wild when I operated the gear though !!! Edited By Chris Bott - Moderator on 17/04/2017 10:07:12 Quote Link to comment Share on other sites More sharing options...
Peter Miller Posted April 16, 2017 Share Posted April 16, 2017 I have seen servo reversers mess things up on one model. When it was removed it cured the problem. Quote Link to comment Share on other sites More sharing options...
John Laverick Posted April 16, 2017 Author Share Posted April 16, 2017 I took all your suggestions on board, and I've just spent the last hour resetting my Tx, changed my Rx, and tried every combination you could think of. Guess what the problem was? Well done Martin, it was a faulty extension lead!!!!!!! I thought I was going nuts? I can't believe that a faulty lead would cause so many problems? No wonder we crash the things all the time. Thanks guys, don't think I would have thought of that? Great forum for help and information. Here's a picture of the plane in question Thanks again John Edited By Chris Bott - Moderator on 16/04/2017 19:48:32 Quote Link to comment Share on other sites More sharing options...
Former Member Posted April 16, 2017 Share Posted April 16, 2017 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted April 17, 2017 Share Posted April 17, 2017 It is usually a poor connection that makes the servo "erratic" . Quote Link to comment Share on other sites More sharing options...
Martian Posted April 17, 2017 Share Posted April 17, 2017 A lovely model just as well you tracked down the problem with the help of the forum sages it would have been a tragedy for it To go in Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted April 17, 2017 Share Posted April 17, 2017 It's often the connection via the sticks Quote Link to comment Share on other sites More sharing options...
John Laverick Posted April 22, 2017 Author Share Posted April 22, 2017 Well, I thought I'd solved it, until I went into the garden to do a test on the Wattmeter to see what the motor was pulling. Then everything went mental again!!! Just buy chance I read on the forum about inbuilt bec's only providing 2 to 3 amps to the servos. Then the penny dropped, I've always used separate Ubec's but for some reason I thought 70 amp Sbec would be sufficient for this model? What a numpty, 7 servos and two of them being electric retracts, of course it would go mental!!! Anyway, I've put a Ubec on it and it all works sweet. I must admit, you would think electric flight Would be plane sailing, but it couldn't be further from the truth. Thanks guys John Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted April 22, 2017 Share Posted April 22, 2017 John Plain sailing?. To be fair I bet the ESC has the BEC amp rating printed on it. . Quote Link to comment Share on other sites More sharing options...
PeterF Posted April 22, 2017 Share Posted April 22, 2017 Hmmm. This is an area of keen interest to me at the moment. 1. A colleague recently had a plane go in and the only thing we could come up with was too small a BEC in the ESC. I have the same model as the one that went in, mine has a 5A BEC in the ESC, theirs had a 3A BEC in the ESC, small F3A type model with mini digital servos, took off and put it into a high energy flick / spin manoeuvre and it went erratic and then recovered control but he was zero mistakes high. 2. I am currently putting together a scale EDF jet that has 2 very high torque (>20kgf) standard size servos, 9 mini servos, all digital plus electric tricycle retracts. I have been trying to find some rules of thumb for sizing the BEC and can not find a lot of information. This topic appears to be lacking in hard and fast rules other than to make it as big as possible. The alternative going through my mind at the moment is to go back to a separate Rx & servo battery. Does anyone have any sage guidance on the sizing of BECs. Edited By PeterF on 22/04/2017 23:09:25 Quote Link to comment Share on other sites More sharing options...
Dave Bran Posted April 23, 2017 Share Posted April 23, 2017 From years ago, whenever the motor current needs bigger than a 40A ESC or there are more than five std or smaller servos I have always used an OPTO ESC and a UBEC. This stemmed from Helicopter use with high power digitals and fast tail servos where all mine from 500 up have them. I do not have much with retract servos being an early adopter of electrical screw type, but no way would I use a BEC ESC on a plane with one alone. It just seemed sensible NOT to have the risk from all eggs in one basket. Not saying this is essential, but the engineer in me wanted it and I have seen no downside, so why not? Quote Link to comment Share on other sites More sharing options...
John Laverick Posted April 23, 2017 Author Share Posted April 23, 2017 Simon, this was one instance where the Bec output wasn't put on the Esc! I agree they normally are. I normally go with the rule of thumb that Dave suggested, 40 amps and over I use an Opto or disconnect the power lead and add a Übec. I think I just got lazy. I think Someone needs to design a Übec that plugs into the power source straight from the Esc instead of having to solder it on? Or, why don't Opto Esc's not come with an attached Übec? Quote Link to comment Share on other sites More sharing options...
Gordon Tarling Posted April 23, 2017 Share Posted April 23, 2017 PeterF - Suggest you use one UBEC for the radio, sized at the highest current rating you can find - I think Castle Creations makes one rated at 20 Amps. Also, use a totally separate UBEC for the retracts - maybe rated at 10 Amps. If the ESC has a built-in BEC, then disconnect or disable it. Even better, use an opto-isolated ESC. Quote Link to comment Share on other sites More sharing options...
Chris Walby Posted April 23, 2017 Share Posted April 23, 2017 Hi, Major word of warning, be very very carful when using digital servos as the instantaneous current draw is very high especially if two or more are driven at once. It will pull the BEC voltage down and take the RX into lost voltage/signal mode, if you are high it might rebind in time, but only if you don't give it loads of stick bashing... I have a HK 6A BEC I can "brown out" with just three small/medium servos on the bench...That bEC is assigned for U?C duty only now! Quote Link to comment Share on other sites More sharing options...
PeterF Posted April 23, 2017 Share Posted April 23, 2017 Posted by Gordon Tarling on 23/04/2017 11:42:12: PeterF - Suggest you use one UBEC for the radio, sized at the highest current rating you can find - I think Castle Creations makes one rated at 20 Amps. Also, use a totally separate UBEC for the retracts - maybe rated at 10 Amps. If the ESC has a built-in BEC, then disconnect or disable it. Even better, use an opto-isolated ESC. Gordon, That is a good idea about the retracts on their own BEC, thanks, Jeti do a BEC to 40 Amps but at a price. The ESCs (twin) are opto isolated. Peter. Quote Link to comment Share on other sites More sharing options...
PeterF Posted April 23, 2017 Share Posted April 23, 2017 Posted by Chris Walby on 23/04/2017 12:06:10: Hi, It will pull the BEC voltage down and take the RX into lost voltage/signal mode, if you are high it might rebind in time, but only if you don't give it loads of stick bashing... Chris, Good to have these reminders. I use Hitec radio gear for this very reason, when I changed to 2.4GHz. The Optima receivers have opto isolators in and you can power the radio function separately to the servo rail, the radio side in all my planes is fed direct from the flight battery. It will take up to 8S feed and as a side benefit you get telemetry of the flight battery back to the Tx. The servo rail is powered from the BEC so no risk of brown outs, only slower servo response. You can choose to power them both from the BEC or single Rx battery pack if desired. Peter. Quote Link to comment Share on other sites More sharing options...
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