Brushless motor with controller question.

[Mike Palko]

If i use a brushless motor on my control line plane how do i get the controller to run wide open? With the astro motor i have now i am running a bec controller which is wide open to start and all you do is turn it on and let go of the plane. Thanks

[steve lewin]

Hi Mike, saw your posts on the Sport forum but I didn't give your (C/L) secret away ;)

The easiest way to get brushless running flat out will be to use a servo tester. These are pretty small and cheap (or very easy to build yourself). Many of the controllers have arming procedures, e.g. start at zero throttle then go to full throttle and back to zero and then it switches on. The servo tester puts out the same signal that the controller would normally get from the R/C receiver and allows you to manually set the output i.e. "throttle level".

I've used this method with standard brushed motors too as many of the newer standard controllers have similar arming procedures.

If you're into electronics it would be easy to program a PIC microcontroller to do the arming automatically but unfortunately there aren't enough C/L fliers to make it worth anyone's while to put anything like that into production so it would be a "Build-it-yourself" project.

Steve

[dynasoar]

Gentlemen,

AMA electric control line speed is active in Southern California. The Class A record holder, Howard Doering has run an Astro FAI 05 (4 turn) powered 7 cell ship at over 90MPH and I have managed 119+ with an AVEOX 1415/02 and 18 cells in Class B.
My commutation electronics ramps up to full speed in about two seconds (to keep the prop on), then is timed to shut off after 35 sec. I would like to modify the module to hold constant current so that I don't over- Amp the commutation fets during the early laps. Any thoughts?

Bill Stewart

[jrb]

I like where we're headed on this one!!!

Maybe ECL is going somewhere now.

Steve was too modest, he's got soem servo tester circuits posted around here that would work well with a BL ESC.

Bill Stewart, could you help us with some diagrams, etc.?

[dynasoar]

JRB,

I'd be glad to forward some attachments showing the airplane etc. Will see what the forum requires me to do.

My background is in fluid dynamics and turbomachines. My electronics capabilities are limited, so please point me at the right places.

Bill Stewart

[jrb]

Servo tester link:

http://www.rcgroups.com/forums/showthread.php?threadid=22533


Another shut-off method:

http://www.rcgroups.com/forums/showthread.php?threadid=9642

Wonder how long they’ll be around?

[Mike Palko]

Wow i'm finally getting some response's! Keep the info, pictures, diagrams, responses ect comeing. I will check out the posted links and see if i can build my own controller. Thanks for the help/interest in this. Mike

[steve lewin]

Originally posted by Mike Palko
Wow i'm finally getting some response's!
Considering I reply to all of your messages I'm still deciding if I should take that as an insult ;).

Anyway, you should note that the relay switches in jrb's second link only work with brushed motors. Brushless motors need a proper 3-phase controller, just switching the battery DC to them won't do it.

Steve

[Mike Palko]

Sorry if i offended anybody. I know there is more than one or two people out there reading this forum. I'm just waiting for them to post. Steve you have done nothing but help me.

[Mike Palko]

Steve the servo tester on your site, does that work for a brushless motor? This could be tough explaining this one to me seeing how i know nothing about electronics other than how to solder.

Have you ever heard of Larry Scribnick(spelling) from SR batteries? When i saw Bob Hunt fly the electric control line he was using the SR Max 10 motor, SR battery pack, and a motor controller made by Larry. Bob gave me his setup but it didn't include the motor controller. I have his number (Larry) but he never answer's the phone when i call him.

If i try to make a motor controller where do i get the parts? Do i start with a esc, or do i by the stuff from radio shack or something along those lines? I hope my questions aren't getting annoying, i hope they are sparking an interest....

[steve lewin]

Quick reply, I'm in a bit of a rush....

It will not be worth your while trying to make a brushless controller, they are complex and need some clever programming of microcontrollers. You couldn't buy the parts for what you'll pay for one. The only practical option is to buy the motor and controller.

If you do that then the servo tester circuits on my site will work with it. The circuits are set up to allow control of the motor down the lines but you can easily mount the whole thing on the plane. Use the version with a variable resistor control, don't use the switched version because it will not start up reliably with an intelligent controller

It would be possible to make a circuit which would allow your launcher to just press a switch but, strangely enough, it would be a more complex circuit and would have to be purpose designed for the particular controller you wanted to use because of the startup (arming) process that I mentioned earlier.

Hope that helps, I'll try to expand a bit when I have more time.

Have you chosen a motor yet ? I'm thinking of trying the Model Motors AXI 2820 because it will run a decent size prop without a gearbox but it's a bit tricky to mount because the whole can rotates so it more or less has to be mounted on a front bulkhead. Any ideas for getting round this would help.

Steve

[Mike Palko]

I am 100% sure i am going to use a brushless motor. I am 95% sure it will be the AXI 2820. I don't want to use a geared motor because to get the power/thrust/watts however you want to say it you need to use a high pitched prop. Control line stunt is flown with props with a pitch of 6 or less for the most part. The reason being wip up (the plane fly's the maneuver faster and faster like loops) especially in the wind. It also helps the model keep it's speed in vertical maneuvers. I prefer lower pitch's like 4-5. On my main stunter i am using a 4 pitch and i love it. You might have known all this but i went thru it just to tell you my reason for wanting direct drive.

What do you think of aveox motors? They seem to have very high performance but it seems to me that the amp draw is high on them. But that seems to be true about most brushless motors. They make much more power but they pull more amps.

Where can i get a servo tester? I've never heard of them before.

[steve lewin]

Hi Mike I'm glad to see we've gone through the same sort of decision making process and come to similar conclusions. The only thing that puts me off the AXI motors is the difficulty of mounting them, particularly on a profile fuselage.

Unfortunately I can't help much with vendors for stuff. I only know English/European vendors. Similarly I haven't had much to do with Aveox motors. They have an excellent reputation but they're VERY expensive over here. Maxcim is another excellent make and I do have one of their motors but they may be a bit heavy for our purposes and, like Aveox, really need a gearbox.

Servo testers are pretty widely available but I've always just built my own on stripboard. The ccts on my site (which I really must update soon) will work or there are plenty of other ccts all over (e.g. http://www.uoguelph.ca/~antoon/gadgets/gadgets.htm). There are a couple of places over here that produce simple kits (e.g. http://www.micronradiocontrol.fsnet.co.uk/) and I guess there must be some where you are too (it seems silly to pay shipping all the way from the UK for such a simple thing).

Steve