Erfolg Posted March 3, 2009 Share Posted March 3, 2009 I have been using a ESC with Bec on one my aircraft. This aircraft seemed bedevilled with loss of control issues, principally when all 4 servos were in use, towards the back end of the anticipated flight session. I have converted this ESC to one which uses a seperate battery pack for the RX and servos. I am now part way through a conversion, on another model, which again will require 4 servos. Is it possible that using a BEC under these conditions be the source of future problems? The type of servos I use are 9g type ie GWS, SG90, Tower Pro etc. Does any one know? Has any one any experience that is relevant? Erfolg Quote Link to comment Share on other sites More sharing options...
Jonathan Lewzey Posted March 3, 2009 Share Posted March 3, 2009 As you seem to have had control issues in the past i would say 'yes'. Best to not use the BEC circuit if in any doubt especially as Tower Pro servos draw a lot of current. Quote Link to comment Share on other sites More sharing options...
ken anderson. Posted March 3, 2009 Share Posted March 3, 2009 hello erfolg-i fly an electric glider with 4 micro servo's in all off the same battery-up till now -no prob's--then again i've heard people say it's a no no--normally the bec or (lvc)*timbo* speak--save getting corrected--can't cope with 4 servo's---this will have set off the automatic timbo alert-get ready for the correct answer............................... ken (sparky/not) anderson............. i'm using 2200mah 3cell/20c lipo/300watt turnigy outrunner/micro 9g servo's............ Quote Link to comment Share on other sites More sharing options...
Dave S. Posted March 3, 2009 Share Posted March 3, 2009 Surely bec and lvc are completely different things, one supplies power to the rx and servos, the other cuts the power to the motor to preserve the power to the rx and servos when the battery is getting low. Then again, I'm new to this electrickery lark, so ma well have got it a about f. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 3, 2009 Share Posted March 3, 2009 Well yes it is possible. Certain combinations of motor esc and servos can give unpredictable results. The BEC of the ESC ( nothing to do with the LVC Ken ) may well be struggling with 4 servos.... a lot depends on the type and quality of the BEC unit - simple cheaper versions are often just linear regulators and they have the added problem of often not working with more than 3 cells as the required voltage drop is just too high to cope with. Better " switching type " BECs are available on many ESCs these days, and can not only cope with higher servo counts, but also higher input voltages. As an alternative to a seperate battery ( which I personally do not like ) consider a seperate "standalone" BEC such as the UBEC device which is powered from the main flight battery but independednt of the ESC BEC. Heres a standalone switch mode 3A unit for the measly sum of just £4 - unbelievable really! Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 3, 2009 Share Posted March 3, 2009 Dave - your A is correctly orientated to your F Quote Link to comment Share on other sites More sharing options...
Dave S. Posted March 3, 2009 Share Posted March 3, 2009 Thanks, Timbo, quite a relief! Quote Link to comment Share on other sites More sharing options...
Erfolg Posted March 3, 2009 Author Share Posted March 3, 2009 Thanks Timbo I will try a GC UBEC. I do not like the extra weight of a seperate battery for the ESC and servos. Although todate on my reconfigured repiared model, it seems to have improved things. I am reluctant to say solved, as I need an extra 60 minutes of air time, to convince myself. So far only 2 flights and approx 5 minutes total. How does a UBEC fit into the battery, ESC, RX and sevo package/system? Erfolg Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 3, 2009 Share Posted March 3, 2009 The UBEC is simply wired permanently to the ESC battery connectors - so in effect when you plug in the flight battery, this also powers up the UBEC - disconnection of the battery obviously disconnecvts it too The output side of the EBEC has a regualr servo style plug which of course is plugged into the receiver battery ( or indeed any other spare ) socket. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 4, 2009 Share Posted March 4, 2009 Reading this thread I have just realised that my "flapped" Wing Dragon uses 5 (small) servos all driven quite happily from the BEC with no problem at all. However the Hamilcar X I am building will have no less than 8, so perhaps that £4 UBEC would be a good idea. Thanks to this wonderful site we don't have to learn things the hard way! Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 4, 2009 Share Posted March 4, 2009 8 servos may require something a little meatier - perhaps 5A rated at least to be safe. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 5, 2009 Share Posted March 5, 2009 Timbo, just a thought. Following the advice on the thread "How many ESCs?" I shall obviously have to use two (on a "Y" lead?), one for each brushless, but as each BEC is rated at 2 amps does this mean the radio (and thus the servos) will have access to 4 amps? Can you in fact run two BECs together or will they fight each other? Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 5, 2009 Share Posted March 5, 2009 They usually fight each other...depends on the ESC - some ( I cant say which ones ) seem to co-exist OK, but my safest advice woud be not to risk it.....especially as good UBECS are relatively cheap these days. I just bought a couple of these.... Quote Link to comment Share on other sites More sharing options...
ken anderson. Posted March 5, 2009 Share Posted March 5, 2009 timbo-just had a look at the g.c. site/ubec's--it's amazing to think how someone can assemble the ubec pack it off to this side of the world and retail it for the price it is and still make a crust(or sticky bun)--watching a program on the tv a couple of week's ago-saying that the factory that put's together the i pod's was also making other brand's of the same gear-in different case's at the same factory---also they stated that there are only two manufacturer's of lcd tv screen's-they make/sell them to other firm's who make case's for them and stick their badge's on them.................. ken anderson..................... Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 5, 2009 Share Posted March 5, 2009 pretty much the norm for almost all electronic gear these days - PCs are a classic example. Guts are pretty much universal, assembled in different factories ) almost all in the far east ) and the "brand" name badge is stuck on the box before it ships. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 5, 2009 Share Posted March 5, 2009 Thanks Timbo Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted March 6, 2009 Share Posted March 6, 2009 Has anyone noticed these UBECs causing interference?? My latest project will have 6 servos so I decided to use a UBEC....wired it up OK plugged everything in (Futaba Rx) to try it. The motor span up ok but started "hunting" ie the revs went up & down slightly......Most odd thought I so I plugged a servo in & that twitched rythmically in time with the motor. I removed the UBEC & ran it all again using the BEC on the ESC & it was fine..no glitching...motor smooth etc.....H'mmm!!! So I put the UBEC back into circuit...same thing...regular glitching...(yes I did isolate the BEC on the ESC!!) So I tried a different Rx...an 8ch Corona unit....perfect....absolutely glitch free!!! So is the Corona unit masking the interference or am I missing something......!!! I am on 35MHz so it could be the high frequency switching of the UBEC is upsetting my Futaba Rx..... Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 6, 2009 Share Posted March 6, 2009 Switching regulators which are used in the better higher power BECs can be "noisy" and some are supplied wiuth metal shielded cases, and ferrite rings on the signal lead. The ESC BEC is probaly a simpler cheaper linear regualtor and therefore noise free. Some recivers are indeed prone to being sensitive to this and others are not. Now of course if you dragged yourself into the 21 st century and bought a 2.4Ghz set.... Quote Link to comment Share on other sites More sharing options...
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