The Wright Stuff Posted March 26, 2013 Share Posted March 26, 2013 Hi there, Sorry - this is a basic question but I can't seem to find the answer here! I've flown for years on IC and 35 MHz, but now got a Futaba 6J (my first programmable transmitter) and also want to learn electric. I bought myself a Parkzone T-28 as a relatively easy-to-fly model on which to get to grips with both electric and 2.4 GHz! It's the PNP version and I am using my Futaba 6J. I've already read that I have to reverse the throttle channel, and it's working OK, but I'm unsure if the throttle range on the Futaba is the same as the Specktrum system that the ESC is presumably factory set up for. For example, how do I know that WOT is actually giving the correct amount of power with the trim at 100%? I'm also concerned that there is a dead zone at the throttle closed position - i.e. I have to open the throttle lever by about 20% before the motor actually starts. Is this usually how they are set up, or should I set it up so that it starts within a few clicks? The ESC manual just talks about 1.2ms to 1.8ms versus 1.1ms to 1.9ms, but I'm not clear how this relates to actual stick positions... can I / should I simply use the channel 3 trim lever to increase the idle speed? I'm also confused by the fact that the throttle trim lever on the modern radios only affects the idle rather than the full range. This might be a good idea for IC engines, but I'm not sure how to set it up for electric, wherre the concept of an idle is (as far as I can see) redundant... Cheers, Ian Edited By Steve Hargreaves - Moderator on 27/03/2013 09:03:31 Quote Link to comment Share on other sites More sharing options...
Biggles' Elder Brother - Moderator Posted March 27, 2013 Share Posted March 27, 2013 Ian, it late at night - and I could move your thread - but frankly I'm a bit tired, and I guess what you really want is simply an answer! So here goes. You have to teach your speed controller your transmitter's throttle range. The way to do this is as follows. (assuming you have the normal Futaba reverse in place - as you seem to!) battery disconnected turn on TX - set throttle to max. Connect battery At the first break in the bleeps immediately move your throttle to zero. That will teach the system your throttle range and all should be well. BEB PS Just as a sensible precaution remove the prop from the model when doing this! Edited By Steve Hargreaves - Moderator on 27/03/2013 09:04:09 Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted March 27, 2013 Share Posted March 27, 2013 Thread moved Ian...... I agree with BEB...it just looks as though you need to "teach" your ESC how to respond to the throttle. Following BEBs intsructions should tell it how to behave.... Quote Link to comment Share on other sites More sharing options...
The Wright Stuff Posted March 27, 2013 Author Share Posted March 27, 2013 Thanks for that chaps - I'll give that a try. Such a simple tip, and yet not in plain English in the ESC instructions. All my instinct wants to do is look at the carburettor movement! It'll be a while before I get out of the habit of taking the fuel bottle with me, though!!! Quote Link to comment Share on other sites More sharing options...
Roy Hill 3 Posted April 16, 2013 Share Posted April 16, 2013 Hello every-one. Will some-one please help me before I go crackers. I have no doubt that the answer is as obvious the rather large nose on my old face but I can't find it! (The answer, that is, not the nose!) I have a Hacker Tornado coupled to a Hacker X80 ESC and a 10S LiPo installed in an 81 inch Taylorcraft. I had it working perfectly before I changed the 'Arming Switch'. When switching on, all in the sequence, I get the correct 'Beeps' from the ESC but when trying to operate the throttle, the motor groans while turning over a few times and then stops. What has gone wrong? Happy Landings, Roy Quote Link to comment Share on other sites More sharing options...
Andy48 Posted April 16, 2013 Share Posted April 16, 2013 If it worked before you fitted an arming switch, and now it doesn't then the problem is down to the wiring of your arming switch. You will need to describe fully how you have wired this up. Quote Link to comment Share on other sites More sharing options...
Roy Hill 3 Posted April 17, 2013 Share Posted April 17, 2013 Hello Martin. At first, I thought that I had wired it up so that the 5.2v flight battery was powering the motor. It wasn't! Wiring is thus.......Pos (+)from LiPo to arming switch then to ESC. The 3 wires from ESC to motor have not been disturbed. Neg (-) from ESC to LiPo complete the curcuit. Incidently, I'm using a Dx6i Tx. I've tried placing the arming switch on the Neg (-) side to no avail. Listening to the tunes coming from the ESC, I think that I might have to reprogram it! What do you think? Regards, Roy Quote Link to comment Share on other sites More sharing options...
The Wright Stuff Posted April 22, 2013 Author Share Posted April 22, 2013 Hi, To get back to my original question on this thread – I’ve been doing some experimentation and thought it’d be useful to record it here for posterity! BEB, it appears that the E-Flite / Parkzone ESCs can’t be auto calibrated in the ‘usual’ manner, but instead can be switched between two input PWM ranges: 1.2 to 1.8 ms (default) and 1.1 to 1.9. My Futaba 6J, on 100% rates and default End Point Adjustment presumably lies in between this range, because there was a significant dead area at each end of the range for 1.2 to 1.8 ms, and insufficient range to arm the ESC and access full throttle with 1.1 to 1.9 ms. I can’t find any data sheet that allows me to convert rates % to real pulse widths, but perhaps I’m overthinking this! . In either case, I just used the End Point Adjustment on the transmitter to set appropriate values. I couldn’t perceive any significant increase in the resolution by increasing the input range. Naturally this leads to two further questions: The first question is technical: it is possible to damage the ESC / motor by leaving it in a state of ‘threshold’ start up? i.e. Not quite enough current to actually turn the prop but not actually fully ‘off’. I know you could burn out old brushed motors by leaving them in this ‘stalled’ state, but I’m guessing it’s less of a problem with modern kit. The second question is really just set-up etiquette. Since my Tx has a separate ‘throttle cut’ switch, I’m tempted to set it up such that stick fully down corresponds to a ‘tick over’ rather than fully stopped (i.e. mimicking an IC model). A couple of reasons: first a stopped prop looks unrealistic on a scale model in flight, and second – from a safety point of view – I’m wondering whether having to use the throttle cut (which cannot be inadvertently knocked) is better than relying on the throttle stick being down (more easily knocked when carrying the model). However, since this is rarely done I guess it might be seen as bad practice. Is that the case? Anyway, happy to receive comments or advice, but it’s probably time to stop fiddling and start flying!!! Cheers. Edited By The Wright Stuff on 22/04/2013 10:32:54 Edited By The Wright Stuff on 22/04/2013 10:34:15 Quote Link to comment Share on other sites More sharing options...
Pete B Posted April 22, 2013 Share Posted April 22, 2013 Posted by The Wright Stuff on 22/04/2013 10:31:26: A couple of reasons: first a stopped prop looks unrealistic on a scale model in flight, and second – from a safety point of view – I’m wondering whether having to use the throttle cut (which cannot be inadvertently knocked) is better than relying on the throttle stick being down (more easily knocked when carrying the model). However, since this is rarely done I guess it might be seen as bad practice. Is that the case? I've recently taken to setting the throttle cut on my DX8 with my power models. Not having any retracts, I've settled on using the gear switch and yes, it certainly does prevent the inadvertent shifting of the throttle stick, so I certainly would see it as good practice. The proviso is, of course, that once the model is 'live', you always assume nothing.... This does give you the option of a 'tickover' setting and I've found this easy enough to set with the trim. In practice, provided you have the motor brake set to 'off', the airflow will turn the prop and provide a not insignificant amount of aerodynamic braking - useful when going downhill! Pete Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted April 22, 2013 Share Posted April 22, 2013 Bear in mind that if you move the trim to dial in some "tickover" and you nose over on landing the motor will draw current to try to keep rotating and you may possibly cause some damage unless you are quick on the throttle cut. Also if you are on Futaba make sure you reset the failsafe after you've reversed the throttle or the failsafe position will be at 100% thottle, while especially so on Futaba because they use the opposite throttle sense it is a sensible precaution on any system to reset the failsafe after the model is set up. I've seen a couple of fliers new to electric inadvertenly switch their Tx off after landing as the motor had stopped for it to start up again........................ Edited By Frank Skilbeck on 22/04/2013 13:21:32 Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted April 22, 2013 Share Posted April 22, 2013 If it hasn't already been said please make sure you remove the prop before messing with ANY ESC or Failsafe settings!!! Also just to take issue with Franks comment about the motor continuing to draw current & try to keep rotating this is not actually true of an "unsensored" brushless motor. Once the motor stops rotating the ESC is no longer receiving back emf signals & "loses track" of where the poles are. Once stopped the motor will stay stopped until the throttle is closed & the ESC can run through its "start up" phase once more. The idea of a mix to render the throttle impotent is certainly a good one though.....I have this set up on my lekky models to prevent any unexpected start ups... Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted April 22, 2013 Share Posted April 22, 2013 Steve are you sure I had an example last week where a flyer had run his motor up, put the undercarriageless plane down and then knocked the throttle and motor continually tried to turn, but of course it's then going through it's start up routine. Maybe it will be something to test one day, I can stop the motor and measure current with the telemetry system and see if it starts again if I release it. Edited By Frank Skilbeck on 22/04/2013 15:33:08 Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted April 22, 2013 Share Posted April 22, 2013 From rest Frank yes it will do exactly that.....the ESC sends a pulse to the windings & "reads" the back emf waveform. From this it detects the position of the magnetic poles & tries to start up the motor but if it is stopped whilst running (ie in a nose over situation whilst idling) the ESC won't know where each pole is because it will no longer be getting anything back from the motor & won't know when to "fire" the o/p transistors so it will shut down & sulk.... If you do test it I'm sure you'll find it works just as described but do mind your fingers..... Brushed motors are different here in that the current is switched by the rotating commutator...a mechanical switch if you like....so they keep trying to turn for as long as there is a voltage applied to the brushes.... Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted April 22, 2013 Share Posted April 22, 2013 I'm going to do it without the prop on a small motor................. Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted April 22, 2013 Share Posted April 22, 2013 Steve I just tried a simple test on a low power 2s motor, set it to about 10% throttle without the prop and gripped the prop shaft and stalled the motor, it was twitching and trying to rotate, the second I let go it started to rotate, I held it stopped for a few seconds and it didn't show any signs of shutting down. It didn't sulk but did it's best to turn the motor, as it was a small motor I didn't have the connectors to hook up my ammeter on the connectors on this battery, it was also hard to stop this motor and I don't think I will be able to easily or brave enough to try stopping a larger motor Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted April 23, 2013 Share Posted April 23, 2013 Thats interesting Frank....I tried it on a couple of my motors when I read about this & they stopped & stayed stopped. I had to close the throttle & reopen it to get the motor rotating again.... I wonder if it varies between ESCs & how their firmware is written....or maybe at such a low speed the ESC is capable of "picking up" the magnets again.... I'm going to have to try a couple of my other motors I think.... Quote Link to comment Share on other sites More sharing options...
Chris Bott - Moderator Posted April 23, 2013 Share Posted April 23, 2013 I have wondered about this. It must depend on the whim of the software programmer. I have seen belly landings where the pilot has forgotten to lower the throttle. One thrashed about madly, another let out rather a lot of smoke! Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted April 23, 2013 Share Posted April 23, 2013 If you think about it the ESC software should cut off the power when the motor stops rotating. If it doesn't then the ESC will still be applying power to the motor windings. With no back emf generated the full voltage will be momentarily applied across the coil windings which is effectively a short circuit....hence the smoke..... This is effectively what happens with a brushed motor. Our ESCs are much more sophistcated than that though so I agree Chris it has to be a software issue.....has the developer considered this issue & written the code to take care of it....? Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted April 23, 2013 Share Posted April 23, 2013 Well a bit more testing tonight....I took 3 models to the shed & the results are inconclusive..... With all three models I set them at low throttle, just over tickover really & drawing about 0.5A (I had my wattmeter in situ).....then I braked the motor can to a standstill. One motor just stopped...& the current dropped to zero. The other 2 stopped & sat there screeching....you know how they do when they lose sync....& the current increased to about 1.5A. Neither of these two motors showed any sign of movement....they held their position but interestingly when I flicked the prop anticlockwise they restarted & ran slowly as before. So I had better qualify my statement that a stopped motor will draw no current......it appears to depends on the ESC used..... Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted April 23, 2013 Share Posted April 23, 2013 Steve, the one I tested was a cheap foamy with it's own bell motor and no name ESC, I'll try it with one of my brand name ESCs, but these are in a bit more powerful models. Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted April 23, 2013 Share Posted April 23, 2013 Hi Frank...yeah mine were the same...budget motors & ESCs in all three cases... Quote Link to comment Share on other sites More sharing options...
Glyn R Posted April 24, 2013 Share Posted April 24, 2013 Posted by Roy Hill 3 on 16/04/2013 17:20:58: Hello every-one. Will some-one please help me before I go crackers. I have no doubt that the answer is as obvious the rather large nose on my old face but I can't find it! (The answer, that is, not the nose!) I have a Hacker Tornado coupled to a Hacker X80 ESC and a 10S LiPo installed in an 81 inch Taylorcraft. I had it working perfectly before I changed the 'Arming Switch'. When switching on, all in the sequence, I get the correct 'Beeps' from the ESC but when trying to operate the throttle, the motor groans while turning over a few times and then stops. What has gone wrong? Happy Landings, Roy I wish I knew Roy I had this same problem with a different set up. I never got to the bottom of it. Quote Link to comment Share on other sites More sharing options...
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