Hi all, I have a project that I would like help with - actually more than help as I have no electronics training.

I'd like to use a pressure differential transducer like this: http://www.omega.com/ppt/pptsc.asp?ref=PX138&Nav=preb05
to drive a 10 LED display. The circuit will illuminate more LED's as the pressure differential equalizes. I poked around enough to think this could be done with a LM3914 but I don't have the knowledge to take this project any further. I imagine I would need some kind of voltage regulator as the power source for this will be an automobile type battery/charging system. I would also need a way to adjust the circuit to define the low and high pressure differential ranges. Having an audio alert when 3 or less LEDS are lite would be and added bonus. Any pilots out there want to guess what this device would be called?

Thanks so much in advance.
Todd Neidinger

 

hi Todd,
The LM3914 sounds a good option for the pressure sensor, with a little extra circuitry and 10 Leds it would give you what you want, also the bleeper on the low ranges.

Are you considering the 15psi version, absolute?

Sounds to me you are thermal hunting for your glider.. ?

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Eric
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Not a pilot but suspect you want to measure the pressure differential of a Pitot tube as airspeed low speed stall alarm?

And yes you will need a voltage regulator to drive the sensor and possibly a op amp to scale the sensosr output voltage and allow for calibration. You also need to figure out a reference to calibrate to, such as a accurate pressure source or another instrument to check against. While not a difficult project it does require some experience with analog electronics and possibly PIC type experience in that a programmable controller chip can help simplify some of the features.

Lefty

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Measurement changes behavior

 

Hello Todd,

I suppose you are planning to make a VSI (vertical speed indicator), VVI (vertical velocity indicator) or Variometer as already guessed here. If you want to use it for stall indication you must apply an angle of attack probe too, since a stall condition can only be determined by speed and angle of attack.

If used as a VSI I suggest to make it indicate ascend, descend and stationary horizontal flight. In that case don't forget a thermo air bottle.

Please tell us more about the application.

Boncuk

 

All your guesses are in the ballpark - I want to make a digital version of this:

http://www.ch601.org/resources/aoa/aoa.htm

The pressure transducer I mentioned in my first post was only a guess. I'm open to other options. The pressure in the analog version uses a 2" of water gauge. The referenced pressure differential transducers are measured in psi. Using an online converter 2" of water is equivalent to 0.07225 psi, so using one of the transducers with a differential range of 0 to 1 psi should work.

Thanks
Todd

 

A big jet takes off and lands with a very high angle of attack. I suppose the engines have enough thrust to create lift, not the wings. The wings act like a kite.

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Uncle $crooge

 

Well actually the wings do provide a huge amount of lift...They just need very high speeds to do it. (That's why F-18s can't glide for long...and there dead without power...).

 

Hi audioguru,

not the engines produce lift, they produce enough thrust to have the wings produce lift. You can make any object fly with high power, even a table or a door which don't have an air foil. A kite doesn't fly based on aerodynamics, it flies by thrust only. If you release a kite it will crash.

 

....enough for a flare.

 

I looked in Google at the old F-18 then wasted a lot of time watching airplane "mishaps". Many airplanes had plenty of thrust to hold them hovering just before they tipped over and crashed.

The video of the RC Lawnmower and the RC Hydrofoam boats shows that anything can be made to fly very well.
http://lib.store.yahoo.net/lib/trend...ydro-racer.wmv

EDIT: Original link didn't work

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Uncle $crooge

 

Yes, everything can fly. If you happen to have a VW bug it will take off at a speed of approximately 165km/h. At 140km/h the appearant weight on each axle is about 15kg which have to be overcome by speed.

 

I received a Chinese RC glider as my father's day gift from my kids. It has an electric motor with folding propeller that is powered from a heavy Ni-MH battery. It flies like a brick, very fast. It stalls easily especially when the battery is near the end of its charge. It doesn't have ailerons so the wind blows it wherever it wants. But it is lots of fun!

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Uncle $crooge

 

Cars can't fly because there's nothing to keep them moving once they've lifted off the ground, as soon as the car starts to lift the wheels will slip causing it to slow down or even crash, if you're going round a corner.

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That's why I talked about take-off, no flight!

To make it fly you need a kind of propulsion like a gas turbine and for maneuverability you'll need control surfaces like with a real plane. Some small wings would be desireable too.

 

There is a video on the web of an RC model B-29 bomber with 4 piston engines. It carries up a little X-1 rocket airplane then drops it. The little plane drops many meters then its rocket starts and propels it very quickly straight up with a smoke trail.

When the rocket fuel has finished then the little airplane does many manouvers with only momentum powering it and it lands smoothly.

The big bomber did some nice manouvers too including flying upside down very close to the ground.

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Uncle $crooge