PING)))(((( RC Helicopter auto retract system

david cook

I just ordered a PING I have a BS2 and the programming board.

I want to have a stand alone retract system that will retract the landing gear at a pre-set distance from the ground.

and then deploy the gear when I drop down to the pre-set altitude.


I know I will need the following items

1. RC servo (standard micro servo)
1. PING sensor
1. Basic stamp module

we all know about the PWM standard rc servos use.

I will need to call 2 different PWM settings
1 for retracted position
1 for deployed position.

I'm a Mechanical Engineer / Radio control nut ( 25+ rc helis.... )

and I have never programmed a basic stamp in my life.

application is for a E-flight Blade CX counter rotating helicopter RTF package ( http://www.horizonhobby.com/Products/Default.aspx?ProdId=EFLH1250 ) comes with a 5 channel TX but a 4 channel RX.

anyway I bought an AIRWOLF Fuselage for my other heli, but decided to install the blade CX mechanics int t since t i soo simple

with the Airwolf body I now need landing gear and this is what drove me to do a Sonar based stand alone automatic system.


has this been done already ? can somebody help me with the coding ? I can trade 3D CAD work for any help, and any help is greatley appreciated.


I'm married with 2 kids and don;t have nearly as much time as I used to..

Dave


"Imagination is more important than knowledge, knowledge is limited, imagination encircles the world." Einstein

Bruce Bates

David -

When using the PBASIC Stamp, PULSEOUT is used to control R/C servos, NOT PWM.

Due to the fact that you have movement in two directions, distance over ground and rising/lowering altitude, you may not get the results you're hoping for with the PING)) sensor.

Regards,

Bruce Bates

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david cook

Thanks Bruce Pulse out is the one to use then.

Hmm Distance over ground and rising/lowering altitude are the same thing to me. what do you mean by this. I just need the system to deploy the landing gear when it gets close enough to the ground ( like 2 feet ) there can even be hysteresis in this. as long as the gear deploys before the body hits the ground then that is good.

Bruce Bates

David -

Think of it as two diffferent vectors: distance over ground divided by time (speed) and altitude rise.·

The following may be a bad analogy, since I'm not an aviator of any sort, but let's give it a try and ask for any appropriate corrections. I'm just going to speak of climb, but descent is just the opposite of climb, or call it negative climb if you wish.

Distance over ground divided by time (speed) is mesured in MPH (or a similar quantity) and altitude rise is measured as rate of climb. One is a somewhat horizontal vector, and the other is a rather vertical vector.

How's that?

Regards,

Bruce Bates

Post Edited (Bruce Bates) : 11/28/2006 5:57:52 PM GMT

allanlane5

Hmm. It sounds to me like you want to install into the body of the Heli a small board, with a BS2 and a 'ping' sensor and a servo. The servo is connected to retractable landing gear.

So, you 'fly' the heli. When you get above a certain altitude (let's say 3 feet) the BS2 with the ping should detect this, and control the servo to raise the landing gear. When you get below a certain altitude (let's say 2.5 feet) the BS2 should lower the landing gear.

This seems very do-able, as long as the Heli can take the weight of the BS2, the ping, the servo, and a 9-volt to run them all.

Edit:· Find attached a simple BS2 program that is a start toward what you want.· Assuming what I said just above is correct.

Edit2:· And now I see it has an on-board 7.2 volt battery, so you don't need a separate battery for the BS2 etc.· How much current does the 'ping' take?· I know the BS2 takes little.

If the servo needs to 'hold' the gear in place, that can take some additional current.· If the gear is very light, maybe you can just activate the servo to move it once, then not command the servo again until ready to land.

Post Edited (allanlane5) : 11/28/2006 6:11:35 PM GMT

allanlane5

Okay, to save power, you probably don't want to 'refresh' the servo all the time.· Hopefully, the gear will stay up, or stay down, 'by themselves' without servo refresh.

So, all you have to do is raise or lower them once.· The attached code does that.




Post Edited (allanlane5) : 11/28/2006 6:29:51 PM GMT

david cook

Allanlane5

you hit the nail on the head that is exactly what I want to do.

the servo on a normal retract setup ( TX has switch for retract option, and RX has spare channel) the servo recieves the command and a non-digital servo will only apply power to keep it in said position. Digital servos are always refreshed .. I would use a non-digital servo in this app.

I am using lithium polymer batteries and have current to spare. and will be tapping into the main battery to power this circuit.

as soon as my PING arrives I will try your code, I can't express enough how much I appreciate this bit of code to get me started. THANK YOU

once I get comfortable with this, I will then program the BS2 to "slowly move the servo" so it looks cooler instead of the landing gear just snapping in and out as fast as the servo can move it.


Bruce yeah now I know what your talking about. good explanation.

Bruce Bates

David -

Based on the information below, I get the impression you can not control the speed of a retract servo:
http://www.servocity.com/html/s136g_compact_retract.html

Regards,

Bruce Bates

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david cook

yes Bruce you are correct, although I will be using a very small 9 oz. standard micro RC servo, so speed is adjustable by controlling the commands to it. ( similar to adjusting your finger speed on the Transmitter sticks).

the servo you found is a high quallity high torque retract for much larger/heavier models.

this is the servo I may use http://www.servocity.com/html/hs-56hb_sub-micro.html

bennettdan

David

I am a Heli Nut also I have the Blade CX1 and CX2 and the CP also...

Nice project I can help you as much as I can the lading gear on the Air Wolf doesnt it come down and out just a little this should allow it to stay down like a over center lock and once down it should stay out with weight on it so the servo refresh is not a problem but what about when it needs to stay retracted?...but the servo should only pull like 7 ma so refresh wont pull too much from the battery.
Do you mind sharing some photos of your Air Wolf Landing gear setup I have been thinking of getting one myself I always...next will be an autopilot for an RC heli when time permits.

I think you would like AllenLane5's first program that will refresh the servo..