19 February 2009

Ashley Circle Burners

The previously reported on informal control line flying has now formalised in to a regular club activity and the folks will be active on a more regular bi - weekly basis. Quite a nice change of pace on Saturday mornings and equiries can be made to Doug on 0835682154.
Those who flew control line way back and are now in to electric RC, may be interested in the development below of a "pic" ic to control a brushless motor and esc for some quiet flight control line. Thanks to Howard and Keith for their feedback on this different approach to U control and over to Howard regarding his devlopment of a pic control:

After reading on the net about flight timers for CL models, I built another ‘prototype’ controller last week so that I could implement a timer function.The circuit is essentially the same as the one I sent you, but with the addition of a super-bright LED that indicates status.
The features are as follows:

A programmable flight timer.
The unit can be programmed to run the motor for a pre-set time.
The default flight time is 3 minutes (180 seconds), but is programmable from 30 seconds, up to 17 minutes, in 30 seconds steps.
The motor RPM will be smoothly reduced to zero, over a 10 second period, once the flight- timer has terminated.
The LED will blink to indicate the end of the flight.
The ESC is automatically disabled at the end of the flight

Programmable RPM (Throttle Setting)
The unit can be programmed to run the motor at any RPM that you choose. This is especially helpful when training a new pilot.
After arming the ESC (by pressing both buttons), you can freely adjust the RPM by pressing the UP and DOWN buttons.
Pressing BOTH buttons simultaneously will ‘memorize’ the (throttle setting) RPM and then bring the RPM to zero.
This ‘memorized’ RPM will be the RPM used when utilizing the Self-Launch timer. (see below)

A self-launch, count-down timer of 12 seconds allows you to fly alone.
After arming the ESC (by pressing both buttons), press and hold the DOWN button to initiate a 12 second count down counter.
The LED will flash at 1 second intervals for 10 seconds, then, flash FAST for the remaining 2 seconds, much like a camera’s self-timer.
The motor will then ramp up to a pre-settable RPM, and then run at that RPM until the flight timer ends.

Manual RPM setting for a flight when a helper can launch the model.
After arming the ESC (by pressing both buttons), you can freely adjust the RPM by pressing the UP an DOWN buttons.
This allows you to adjust the RPM to a setting you are happy with, then have a helper hold the model until you are ready to fly.
The flight timer is automatically started once the ESC is armed, but will be re-started after each time you press a button.

I decided that I needed to test it properly, so I built this little SIG ‘Shoestring” on Friday night.
It’s essentially a ‘plank’ profile plane. The wing is carved/sanded to a semi-symmetrical shape.
I mounted an EMAX 28-12 brushless motor (with 2 degrees right thrust), 8x3.8 prop, E-Flight 20Amp ESC
and a 3cell 1000mAh Lipo pack (positioned to set CG as the plan indicated).
By adjusting the RPM with the UP and DOWN buttons, and using my Eagle-Tree data logger, I set the RPM to 8500.
The motor was drawing 6.5 amps, which would comfortably give 6 minutes duration.
I pressed BOTH buttons to memorize this throttle setting.
I then set the timer function for 3 minutes……

After 30 coats of ‘looking at’ I went to bed.

Saturday morning dawned with perfect weather, off to the field I went….
I put the model on the freshly cut grass, rolled out and un-twisted the lines and connected the battery.
Pressed both buttons to ‘arm’ the ESC, waited for the ‘tell-tale’ beeps from the SEC, and held the DOWN button for
1 second to initiate the 12 second, self-launch timer.
I walked to where the handle was lying, picked it up, checked control direction, UP = up, DOWN = down, and waited ……
The super bright BLUE led blinked at 1 second intervals for what seemed like an eternity……

Then the LED started flashing FAST, and the prop spun up….
In 6 feet she was flying! Wow! Elevator response was good, tension on the lines was fine…..
After a good few ‘re-learning’ laps, I did a wing-over, then a loop, then inverted (which required a lot of down elevator)
3 minutes is a long time…. I wondered if it would ever end!
But sure enough, the motor slowly slowed to a stop, and she settled perfectly for a 3 point landing.
I just stood there thinking, “ I’m 13 again! “


1 comment:

Anonymous said...

Now this is magic! Is it possible that I can have details on the little timer. My dad of 75 would enjoy this a lot.