pitch control sensor

[HSM1986]

hi , i'm doing my project about a remote controlling an airplane with a feedback , and i faced a problem in the pitch control where i couldn't find an accelerometer sensor in my country, but i have found a tilt sensor so can i use it instead??.
if the tilt sensor won't work can u plz tell me what do ! maybe if u have any other idea that i can use plz tell it to me??? coz it's very important .

 

[jpanhalt]

A common sensor detects the light difference between the horizon and the ground. Check Tower Hobbies in the USA. Such sensors are also incorporated in some of the inexpensive, learner aircraft models.

John

 

[HSM1986]

thanx john for stopping by, but u didn't tell me if a tilt sensor will work fro sensing the pitch angle of the airplane??!!

 

[Sceadwian]

tilt sensors usually trigger logic outputs when the pitch exceeds a certain angle, this isn't good enough for level control. If you can purchase a radio control airplane you can purchase pitch sensors, they're called gyros. You can get them at any store that sells helicopters, they can be aligned to any axis and output a signal just like that of a servo proportional to the angular velocity.

 

[Boomslang]

The ligh sensor setup to detect pitch, does not work very well. Thermopiles work allot better. I am also busy with the same type of project, and use the FMA co-pilot (**broken link removed**) for attitude sensing, a 5Hz update rate GPS (GPS) for speed, position and high altitude and a ultrasonic ranger (Sonar) for near ground altitude.
You can also order accelerometers and gyro's etc. from the Sparkfun links above.
The guys at http://www.diydrones.com/ will also be able to help you.

 

[HSM1986]

hi everybody & thanx for ur replies.
boomslang i noticed in ur reply that u r using an ultrasonic sensor for controlling the attitude of the airplane, i'm trying to do the same too.
so i wanna ask u, by what r u going to control the ultrsonic sensor, is it by using 555 IC or using the MCU ?
and what's ur control distanc for the airplane?

 

[Boomslang]

Follow the links I posted in the reply, the ultrasonic sensor is for altitude, not attitude. The senosor in the link I posted have all the control circuitry built in, you just connect it to your MCU with SPI or ADC.
I tried building the ultrasonic sensor myself, but it was not nearly as accurate as the pre-built sensor from sparkfun.

 

[HSM1986]

hi again, and thanx for the link ,but i'm not using MCU in my project .
i'm using 555 timer IC with a counter so i guss that it's not the same...

 

[HSM1986]

do u know any thing about that kind of connection?

 

[Boomslang]

I don't understand, what exactly are you trying to build? Without a MCU you would be very limited.
SPI is a serial interface (like the serial port on your PC), and ADC stands for "Analog to digital conversion", both of which are very common on MCU's.

 

[HSM1986]

well i know that without using the MCU, i will have a littel comlicated circuit!! but u c , my supervisor doesn't allow us to use the microcontroller, coz it will be too simple!
so me and my freind have 4 goals in our projects which are:
1.PC to RC transmitter control of the airplane.
2.altitude control so the airplane doesn't axceed the range of 4 meters.
3.pitch angle control for no more than ْ15.
4.yaw angle control also for no more than 30 degree.
for the second goal our supervisor told us to use the 555 timer IC to trigger the ultrasonic, at the same time a 74163counter will start to count,and when the receiver part of the UltraSonic sensor receives the signal from the transmitter, it will stop the counter and then the value of the counter goes to a DAC IC and the resulted analog value will be compared to another specific value that indicate a 4 meter distance.
then the airplane will re-act upon the measured altitude..
i only asked to find out if there's another way to get the same result without using a microcontroller.
sorry for the long details, but i just wanted to put u in the picture.
thanx in advance

 

[Boomslang]

Pitch and yaw sensing without gyros is close to impossible on airplanes. The acelerometer is effected by the G forces in a turn/climb. In short: a accelorometer is accurate over the long-term and a gyro is accurate short-term.
You could still use the thermopiles without a MCU (they will not work indoors). You can use the analog differential between the left/right or fwd/rear sensors to make the servo turn a certain direction, but that's still a bit of a crude way to do things.
Good luck at flying the plane only 4m off the ground for extended periods while under autonomous control... that will take some doing!

 

[HSM1986]

hi boomslang, thanx for ur reply.
but i want to ask u do u know a good type of an accelerometer that can help me in reading the pitch angle?
and i know that there's a gyroscope IC called ADXRS150EB, so will it work in my project??

 

[HSM1986]

and if any one knows any electronic company in north afric or the middle east that supplies that kind of parts please tell me..
thanx in advance

 

[Boomslang]

Yes, that gyro will work. I am in africa as well, and Sparkfun is the easiest way to get hold of these kind of parts at reasonable prices.
I am using this accelerometer: https://www.sparkfun.com/commerce/product_info.php?products_id=252
You use the accelerometer to compensate for gyro drift... don't know how you are going to do that without a MCU.... I just don't see how you will get your project flying without a MCU to do some thinking/maths...

 

[Mikebits]

Sounds like the plan is to use the PC comm link as the brains, but with ultrasonic, the data rate will be very slow, and may not be able to react quick enough to make needed flight corrections. My 2 stones worth

Are your not allowed to use a MCU, I guess I should go back and read the old post.

 

[Boomslang]

Oh, that makes more sense... I will not trust Windows as the host for my AP brain. Most projects have the brain in the airplane and only some basic control commands are sent from the ground station. You will still need some kind of fail safe in the plane if the links is lost to the base.

 

[Boomslang]

You say you are living in the middle east, hope you are not planning some one-way low flying (under radar) missions...

 

[Mikebits]

You say you are living in the middle east, hope you are not planning some one-way low flying (under radar) missions...

Now, now. Besides with an ultrasonic link I think all is safe.

 

[Boomslang]

Does he want to use the ultrasonic as the link between the base and plane? I thought he want to use it to measure altitude. How are you going to fly a plane in a 6m radius? Maybe I just missunderstood your and his posts... confusing stuff...haha