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Old Jan 13, 2014, 11:43 PM
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Auto Timer / Possible ?

The people in this forum I figure would know. In flying electric sailplanes in ALES contest, there is always a need for a person to time your flight. In most cases the objective is to launch and then land as close to 10 min. as possible. I am wondering if someone could design a timer (carried in the sailplane) that would start timing as soon as it leaves your hand, and stop timing as soon as the sailplane touches the ground. It could be an official time, without the need of a second person timing. I'm thinking of maybe a small patch of touch sensitive tape placed on the fuse, were you would normally hold it for launch, and maybe some sort of micro switch on the bottom of the fuse to stop the timer, on landing. This would also negate any errors made by a human timer. In a contest, just a few seconds off in timing, could make a difference. So, is this possible and how could it be done ? The readout would only need 3 segments up to 999 seconds as a 10 min. task would be 600 seconds. The pilot could use the timer on the Xmiter for his reference, but the timer in the sailplane would be the official time.
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Old Jan 15, 2014, 09:06 AM
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The launch part would be easy, maybe a darlington transistor or capacitive touch type design contacts to start it.

Not sure about the landing part though (I'm assuming it wouldn't be good to have a wire dangling from the aircraft, as this would create drag?) Maybe an IR emitter/detector or ultrasonic set to measure the distance from ground? Heck, I'm not sure.

There is a nifty project a fellow did on instructables a while back on making an accurate clock with the arduino without an RTC or different crystal. To keep weight down, an SMD version of the micro on a small board should be fine. Here is the project:
http://www.instructables.com/id/Make...only-one-wire/
I didn't read in depth but it looks like he is measuring a PWM output using an interrupt.

You wouldn't want an LCD because of weight, maybe some SMD LED's to either flash a code (less components this way) to tell the minutes/seconds, or, LED's arranged like a binary clock (would have a coolness factor, and you'd only need minutes/seconds)
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Old Jan 15, 2014, 12:05 PM
"MAYONNAISE"
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Le Treport, France
Joined Jun 2004
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Hi, Roger ...

great news !!! it exists ...

http://plane-expert.com/index.php?co..._attachment=20

Here for the details ...
http://www.aerobtec.com/products/rc-...nics/altis-v4/

available here ...
http://www.espritmodel.com/aerobtec-...4-fai-f5j.aspx

Alain
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Old Jan 15, 2014, 01:08 PM
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Thanks Alain. But what I'm reading on the Esprit site is for altitude, not to time a sailplane when it leaves your hand, and then touches the ground. With all the other electronics we have for the hobby, this is something that just can't be figured out, in how to do it. Can not be done I guess. Must have another person with a stop watch.
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Old Jan 15, 2014, 01:54 PM
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Just an idea:
The glider is hand launched and during landing decelaration is several magnitudes greater than what is possible to occure during flight. So, just a sensor to measure fore-aft acceleration, a processor and some software should be able to do the job. Maybe add a bluetooth or wifi link to send the data straight to cd's computer or smart phone.
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Old Jan 15, 2014, 02:05 PM
Stuart
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Quote:
Originally Posted by jkettu View Post
Just an idea:
The glider is hand launched and during landing decelaration is several magnitudes greater than what is possible to occure during flight. So, just a sensor to measure fore-aft acceleration, a processor and some software should be able to do the job. Maybe add a bluetooth or wifi link to send the data straight to cd's computer or smart phone.
You have never seen a plane apparently hover, as in stay stationary relative to the ground ?

All you need is a bit of wind.
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Old Jan 15, 2014, 02:16 PM
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What's that got to do with acceleration?
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Old Jan 15, 2014, 02:19 PM
Stuart
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Quote:
Originally Posted by jkettu View Post
What's that got to do with acceleration?
As the plane comes into and settles in the hover, it has no 'fore-aft acceleration' but has not landed.
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Old Jan 15, 2014, 02:35 PM
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That's just the point. It doesn't have significant acceleration during flight, regardless if it is apparently "hovering" or not. During launch it goes from zero to flying speed within couple of feet and maybe a tenth of a second. Landing might be a little less aggressive, but still it would produce a clear spike on acceleration curve.
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Old Jan 15, 2014, 03:11 PM
Stuart
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Quote:
Originally Posted by jkettu View Post
but still it would produce a clear spike on acceleration curve.
You sure ?

Many a time I have landed a plane in long grass and I doubt very much there is any 'spike' in acceleration or deceleration that you could reliably detect.

And then there is low cut smooth wet grass, planes can will skid along the ground for a long way.

I am not saying it cannot be done, but is it easy to specify in a precise way, using acceleration sensors alone, the exact point at which a plane has landed ?
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Old Jan 16, 2014, 02:14 AM
"MAYONNAISE"
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Quote:
Originally Posted by Roger Rocket View Post
Thanks Alain. But what I'm reading on the Esprit site is for altitude, not to time a sailplane when it leaves your hand, and then touches the ground. With all the other electronics we have for the hobby, this is something that just can't be figured out, in how to do it. Can not be done I guess. Must have another person with a stop watch.
I think you read it wayyyyy too fast ....

just have a look closer ... to what it can do.

Alain
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Old Jan 16, 2014, 03:33 AM
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Hi Alain, I did read the Esprit description very carefully and it says nothing about timing a sailplane once it leaves your hand, until it touches the ground. The description reads, Functions : altimeter, thermometer, altitude switch, telemetry.
Where am I missing it, about a timer ?
You know, if someone could come up with an auto timer design, I bet they could sell a few thousand of them worldwide. By the way Alain, thanks for the other links, but they won't download to my IPhone, for some reason, just the Esprit web site.
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Old Jan 16, 2014, 04:34 AM
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Hillbillybrewer, in post # 2 you were seeking a small LCD.
Would this one suit?

1X4 LCD Display
13.5 X 12 X 6mm
Internal I2C controller

It would appear that the ALES rules would allow a motor protector skid which does not offer drag which could act as a switch on landing.

Dave

[Any device, fixed or retractable, intended to arrest the model aircraft on the ground during landing is prohibited.]
(GDS&HS)

http://www.hexpertsystems.com/LCD/
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Old Jan 16, 2014, 09:44 AM
"MAYONNAISE"
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Le Treport, France
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Quote:
Originally Posted by Roger Rocket View Post
Hi Alain, I did read the Esprit description very carefully and it says nothing about timing a sailplane once it leaves your hand, until it touches the ground. The description reads, Functions : altimeter, thermometer, altitude switch, telemetry.
Where am I missing it, about a timer ?
You know, if someone could come up with an auto timer design, I bet they could sell a few thousand of them worldwide. By the way Alain, thanks for the other links, but they won't download to my IPhone, for some reason, just the Esprit web site.
missing all the data stored is time stamped, so you can read your data from a notebook ... and get your flying time.
not exactly real time but enough for training ...

further, it can record your throttle stick position , even if you have passed the programmed switchoff time/altitude . just place throttle back to stop position when landing ... as motor already is off ...

BTW, By using a second receiver on ground, you also can drive a BIG display chromometer ...

But, talking frankly ... my Transmitter ( 25 years old ! ) can start its chrono by raising the throttle stick and/or stopping it by pulling it back.

plus, it has a progressive time warning beeper to tell you it's time to land.

the aerobtec Gizmo can stop your motor automatically, so you have everything you need here for training.

a fully automatic thing ( THE official "Roy Bean" Judge ? ) is ... I think, a full view of mind ...

Alain
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Old Jan 16, 2014, 09:50 AM
Dave the Rave
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I built a free-flight timer for a friend of mine a few years ago, it mounts inside the plane and runs the motor for exactly 15 or 30 seconds (there's a jumper on the circuit board that let's you decide which) before cutting the motor off and allowing the plane to glide for either 2 or 3 minutes (another jumper). Once the glide period is over, it moves a servo that causes the plane to lose altitude and land.

The timing on the motor was accomplished by the use of a small tactile pushbutton switch on the fuse. You press and hold it, and it starts the motor running, the timing begins when the plane is launched and it leaves your hand (button is released). You could do the same thing to start your timer, holding the button down would start the program, releasing the button would start the timing function. To stop the timer, the circuit could look for a signal from the transmitter, as soon as it touches the ground you flip a switch on your radio and stop the timer. The timer's value could be read out to a single LED in minutes and seconds, i.e. 2 flashes, pause, 30 flashes means 2 minutes 30 seconds. Simple, wouldn't take a big chip or a lot of parts, and would be very accurate if the programming is done correctly.

Just some ideas.......................
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