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Old Apr 02, 2002, 12:26 PM
Eat, Sleep, Fly!
realglow's Avatar
Joined Mar 2001
659 Posts
Next Gen DU RX?

Dan,

I know it's too early to expect another version, but let me put in my wish list for the next gen DU RX:

* 3 Channels is OK; 4 would be great.
* Battery voltage of 0.8v to 5v is OK.
* Increase the motor current to 2A
* Make the connectors on the edge for lower profile;
motor on one end; actuator connectors on the other end;
antenna connector on one side; battery connectors on other.
I really like the micro connectors with 0.1 inch spacing that you
used. There is a miniature connector that fits nicely and is very
tiny and lite. Opualuan sells them for $0.20 each!
* Fix the reverse throttle to normal (desirable, not critical)

I would assume you could accomplish this with very little penalty in weight or size using your current technologies.

A nice addition would be a separate dc-dc converter that would operate from 1 to 3 cells and output up to 2 amps at 5 volts. Using the micro technology, of course.

Let me elaborate on the request for higher motor current:

Generally-accepted electric guidelines indicate you need a about 55 watts per pound to get into the aerobatic range of flying. With the current DU RX specs, you are allowed up to 1A at 5v which will probably end up at about 4.5 volts to the motor; that is 4.5 watts. With 4 cells, you are likely to be in the 1.4 ounce area with current lite building techniques, or about 51.3 watts per pound. (correct me if I have mis-calculated) That puts us on the low end of performance; anything less than about 45 watts per pound is probably marginal, limited to a few circuits of level flight and maybe a couple of touch and go passes.

Consider a 2A motor limitation, however and you vault into the high performance area of 85 to 100 watts per pound! Not in the unlimited vertical range, but close. Of course, the higher currents limit the time in the air, so each builder/flyer would have to factor that into his own performance goals.

BTW: I want to congratulate your Dad on the DU RFFS100 RX design. It is definitely a breakthru in cost/performance for the micro application. I am a recently retired circuit designer with more than 30 years in integrated circuit design and application experience. I am thoroughly happy with the RX design, tho a little frustrated with micro plane design/fab due primarily to my stubby fingers and weak eyes! But enjoying every minute of it...
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Old Apr 02, 2002, 12:45 PM
in persuit of low wing loading
Gordon Johnson's Avatar
Boston, Mass
Joined May 2001
6,431 Posts
Dan,
I second James on the DC-DC converter suggestion. If your dad, or you, could come up with a separate DC-DC converter for a reasonable price, you would further revolutionize micro flight. I'd suggest looking at what has been done, and then consider the new forthcoming higher efficiency chip from Texas Instruments (someone started a thread on it).

James' other wish list suggestions are well thought out and I second them as well. I'm not a EE or circuit designer, so I'm way out of my league here. I defer to James and others.
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Old Apr 02, 2002, 01:27 PM
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jberg's Avatar
MSC Rödinghausen, Germany
Joined Feb 2001
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You have to take into account that these 5V/2A have to come out of the battery with ~90% efficiency. A battery that can deliver 11 watts can easily have enough cells without needing a DC-DC converter. The motors that take these 10 watts are bigger also. The DC5-2.4 goes up to 8W; the motor of choice for 10W would be the new Faulhaber DC1717SR IMHO. But you need 8V/1.2A for them, not 5V/2A.

In my opinion the main reason for DC boosters is to use less cells in cases where even the smallest available cells are too heavy when 4 are used. My reason to build a DC booster was to get 5V out of a *single* Lithium cell (yes, I'm a duration guy; I like to land when I'm finally bored, not when the battery is empty ).
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Old Apr 02, 2002, 02:29 PM
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USA, FL, Fort Lauderdale
Joined Feb 2002
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I'll put my two cents in. I think there is a spot in the 2-4 oz. size range (18" or so) where a DU type system would sell. 2 amp esc. with a bit more power for slightly larger coil/magnet actuators. Right now this is the domain of the $60 WesTec servos, a bit pricey. Coils are cheap enough to build in, and swap the rec/esc between planes. I fly only outdoors, so a little more size would be nice, without going all the way to the GWS/Pico size range.

Dave W.
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Old Apr 02, 2002, 02:29 PM
Eat, Sleep, Fly!
realglow's Avatar
Joined Mar 2001
659 Posts
Motor?

OK, then how do we get a 8-10 W brushless motor for micro applications?
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Last edited by realglow; Apr 02, 2002 at 02:32 PM.
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Old Apr 02, 2002, 09:12 PM
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opualuan's Avatar
San Jose, CA
Joined Sep 2001
3,863 Posts
micromo/faulhaber 1628, 16mm diameter. just over an ounce. 11w, 12v. finding lower voltage micro motors was tried before, it is very tough to find anything. xtrem energy has a 12mm gws-size one, but ut;s steel cased nd heavy, and wound for 24v, and very expensive, even though the specs look good...
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Old Apr 03, 2002, 12:21 AM
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Houston Texas
Joined Mar 2001
743 Posts
Re: Motor?

Quote:
Originally posted by realglow
OK, then how do we get a 8-10 W brushless motor for micro applications?
Now that is some thing I would drop another hundred bucks on

Dan I think your father's product is an answer to a many dreams, and now my next dream is a micro brushless motor.

Philip
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Old Apr 03, 2002, 03:03 AM
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jberg's Avatar
MSC Rödinghausen, Germany
Joined Feb 2001
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Quote:
Originally posted by opualuan
micromo/faulhaber 1628, 16mm diameter. just over an ounce. 11w, 12v. finding lower voltage micro motors was tried before, it is very tough to find anything. xtrem energy has a 12mm gws-size one, but ut;s steel cased nd heavy, and wound for 24v, and very expensive, even though the specs look good...
The Faulhaber motor has a rpm level of 40.000-65.000, so you need a good gearbox to convert that to an usable level. I think the "Mini LRK" homebuilt motor concept is much more promising as it is a high-torque design which does not need a gearbox.
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Old Apr 03, 2002, 03:18 AM
high-speed freak
opualuan's Avatar
San Jose, CA
Joined Sep 2001
3,863 Posts
yes, it's interesting, but a gearbox gives more options... do you have an english-language link? I remember it being relatively large, although the design could be scaled... IF you have the tools and expertise!
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Old Apr 03, 2002, 05:06 PM
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tim_j-rome's Avatar
Toronto, Ontario, Canada
Joined Dec 2001
166 Posts
good idea

Hi all,
I think that these improvements would be a great idea--if the cost and weight coulb be kept down. Other than that comment, keep up the great work!
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Old Apr 03, 2002, 06:04 PM
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MSC Rödinghausen, Germany
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Quote:
Originally posted by opualuan
... do you have an english-language link?
Start here!
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Old Apr 03, 2002, 06:12 PM
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Markle, In. US
Joined Oct 2000
196 Posts
I like the ideas of the lrk motor. In fact we do have a supply of parts for these motors. They come in the form of a stepper motor used in the hard drives of our computers. These motors are usually 12 pole and already have the ring magnets with the individual poles around them. I have been looking into this. My thought is one could be created that easily weighs less than an ounce. No time though is the problem.....
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