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Old Jan 25, 2006, 07:28 PM
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Toronto Canada
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Aeroace - Low Speed Throttle Modification

My Aeroace even with one wing will climb at the lowest throttle setting.

For this reason I wanted to reduce the throttle at low speed settings even further.

Some have put resistors or diodes in series with the motors, but this is inefficient and also reduces full throttle power.

By using a 555 timer and pulsing the throttle to set it to zero with a 50% duty cycle it is possible to fly even slower.

The circuit below pulses at approximately 2 times per second.

The 2N3904 transistor disables the circuit at the higher throttle settings by means of a signal from P12 on the throttle stick.

It is not necessary to cut any traces. The only modification to the board is to remove the green wire from P10 and the blue wire from P11 and add the two 10K resistors. Wires are then soldered from the circuit to the appropriate places on the board.

I made the circuit "Manhattan style" and just placed it inside the case near the throttle stick.

It took me approximately 2 hours from start to finish.

The 2 diode zero throttle turning mod is no longer connected to P11, but is connected to the blue wire coming from the throttle.

I haven't flown it yet, but I would be grateful for any feedback from those adventuresome souls who might try it.
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Last edited by Martyn McKinney; Jan 25, 2006 at 09:29 PM.
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Old Jan 25, 2006, 08:30 PM
iPhly R/C with iPhone
iter's Avatar
Silicon Valley, Calif
Joined Jan 2005
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I haven't tried it with the AA yet, but I tried to do low frequency throttle PWM from the transmitter on a WAMF. (had it driven from a parallel port, too). WAMF uses the TX2 chip, and that won't do more than about 3Hz. What I and RCcam (http://members.aol.com/rchelicam/microszr/microszr.htm) found out was that it's too slow for smooth flight. The plane has enough time between pulses to drop the nose, and it flies in series of violent PIO (PWM Induced Oscilations). But the AA may be different. Let us know how it works out.

Ari.
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Old Jan 25, 2006, 10:17 PM
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widgeteer's Avatar
lower Michigan-utica
Joined Dec 2005
286 Posts
Wow, you people rule. I can almost understand what you say. (Stick around this site long enough, you learn lots of stuff). I gotta try that throttle thing, seems that could help to make this bird into a real 'L R F' , just takes time to put the pieces together. Gimme more, please.
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Old Jan 25, 2006, 10:34 PM
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riverside, CA
Joined Feb 2003
725 Posts
Nice "circuit bend" without harming whats there already. Good job
Casey
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Old Jan 25, 2006, 11:53 PM
I crash A LOT
Joined Jan 2006
33 Posts
I am sure the answer is somewhere in the thousands of posts about the AA, but what is the update rate of radio?
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Old Jan 26, 2006, 02:37 AM
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NRW, Germany
Joined Apr 2004
711 Posts
Iter is right, I think. We (RolfPW + I) made some tests and first you should synchronize the toggling with the tx-frames and second the standard frames per second are is to slow for smooth control.
With 10fps (= 5 toggles per second) it starts to become a good feeling.

But its worth a try, everything concernig the AA is worth a try

Quax
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Old Jan 26, 2006, 07:29 AM
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Toronto Canada
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Quax:

When you designed your system did you find a microcontroller output on the stock transmitter that could be used for synchronizing on the transmit frames ?

If not, it might be possible to create one by lowpassing the output of the microcontroller driving Q4 through R17.

Whitehot:

Channel A 4 frames per second
Channel B 6 frames per second
Channel C 5 frames per second

http://home.versanet.de/~b-konze/xtwin/info/info_en.htm
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Old Jan 26, 2006, 09:32 AM
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If you want to fly slower, wouldn't it be easier to just turn the props around backwards?...or trim a little off of them....or bend some of the pitch out of them?
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Old Jan 26, 2006, 10:12 AM
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Toronto Canada
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I tried putting the props on backwards but there wasn't enough thrust.

If they are trimmed you lose full throttle performance.

Others have suggested adding weight, but I want the plane to fly slower, not faster.
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Old Jan 26, 2006, 12:36 PM
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NRW, Germany
Joined Apr 2004
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Martyn McKinney,

someone shortened the props and made them a little bit smaller the same time. Maybe the best solution to lower thrust and being stingy with energy .

Quote:
If not, it might be possible to create one by lowpassing the output of the microcontroller driving Q4 through R17.
Should work, I would toggle a flip/flop with the falling edge, means the end of each frame. And then using channel B should go quite well.

Quax
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Old Jan 26, 2006, 12:53 PM
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Toronto Canada
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Quax:

Thanks for your input.

After playing with this for a while and reviewing your comments, I'm going to go back to the drawing board.

I realize now that to ensure reliability a 50% duty cycle will require toggling on alternate frames which is going to require some type of clocking flipflop.

I had qualms about posting this prematurely, but I wanted to get some feedback which both you and Iter provided. Thanks again.

I'll be back !
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Old Jan 27, 2006, 05:00 PM
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Toronto Canada
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Here is the circuit that I came up with to reduce the throttle by setting it to zero by synchronizing the pulsing with the transmitter frame rate.

Although the original 555 timer circuit worked, it was not consistant.

The circuit below turns the throttle off at the lower throttle settings with a duty cycle of 50%.

The pulses used to modulate the transmitter, trigger a D flip-flop, the output of which turns off the throttle.

If there were an odd number of transitions in each frame, only one flip-flop would be necessary. There are an even number, however.

Adding the second flip-flop gives an output which is high for 50% of the time.

At the higher throttle settings, this circuit is inhibited by a signal from the throttle stick P12 (violet wire) which turns on the transistor, thus setting the flip-flops to a high state.

The 2 diode zero throttle turning mod remains at P11.

Because the frame rate of this transmitter on Channel A is quite low, the motor is turned on only twice per second. I would expect to see an improvement in performance if a Channel B transmitter were used.

The only modification to the board is to remove the yellow COMMON wire from the throttle encoder. This yellow wire is then used to provide power to the circuit.

The COMMON on the throttle encoder (where the yellow wire was removed) is connected to the diode coming from the output of the second flip-flop.

By ORing other diodes from the output of the flip-flops, other duty cycles are possible.

This might require deriving a different clock by using an extra transistor, however.

Purists might note that I have failed to include pull up resistors on some of the inputs. Because this is a TTL device the inputs of which use current sinking and simplicity was a factor, I have chosen to leave them out.

If a CMOS device were used they would be required.

EDIT:

I just flew both my stock Aeroace and my extended wing Aeroace with this mod and it works quite well even with a Channel A system. No sign of porpoising even at the 2Hz pulsing rate.

At low throttle it just barely holds altitude and is over-ridden by the turning mod when turns are made. Previously I had problems flying at any throttle setting because the plane would gain too much altitude.

It might be worthwhile trying 75% duty cycle, which would require an extra flip-flop and diode or a different clock and extra diode.
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Old Feb 01, 2006, 04:40 AM
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couldnt you use a transistor to turn off the zero throttle diode mod when you are NOT at zero throttle? Then you wouldnt effect the turning speeds on all 7 throttle settings.

couldnt you have p12 trigger a transistor to disconnect the diodes?
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Old Feb 01, 2006, 07:42 AM
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Toronto Canada
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Yes, but the circuits that I came up with were more complicated than the 2 diode mod and the benefit didn't seem worth it.

The motor speeds used for turning are determined by the software in the transmitter encoder and it was difficult to notice any difference between turning with the diode mod and without it.
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Old Feb 01, 2006, 03:48 PM
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Quote:
Originally Posted by Martyn McKinney
Yes, but the circuits that I came up with were more complicated than the 2 diode mod and the benefit didn't seem worth it.

The motor speeds used for turning are determined by the software in the receiver decoder and it was difficult to notice any difference between turning with the diode mod and without it.
yeah, I understand the new low throttle circuit.. I also did the diode mod and like it.. I was just kinda concerned that it was effecting the turning speeds at diffferent throttle settings since that p11 bit is always on when turning now.. but if it does make much difference than no since in making it more complicated..

Did this low throttle mod turn out to be worthwile? I guess you dropped the 555 version.
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