Satellite Antenna Tracker

Hello,

I am working on an antenna rotor, that will move my antenna array around at any azimuth (0-360 degrees). To insure accuracy i am going to use this Adafruit HMC5883L Breakout - Triple-Axis Magnetometer/Compass Sensor to report the azimuth and eventually elevation the antenna array is pointing.

As a motor, I want to use a wiper motor. This is because i will have 4 antennas on this project, the rotating mass might be around 5 pounds. A wiper motor seems to be perfect for this.

But a wiper motor is just a DC motor? Can any DC motor controller run this? I need one that is bi direction. I figure the motor i want will be around 10 amps, so i need to find the correct controller the allows the much current.

Anyone have any thoughts on this? For control, i have a program written that communicates with the arduino uno via serial connection, and will have 5 check points during a satellite pass, so that i dont have to go outside and move it my self.

Thanks.

Why not just have position sensors on the bearing axles?

Pololu has an excellent line of motor controllers.

The magnetometer will not give accurate azimuth readings if not properly calibrated in the final installation.

aarg:
Why not just have position sensors on the bearing axles?

Something like a potentiometer? That is a thought. I have seen people do it in other projects, ill have to look into how I can translate that into mine.

jremington:
Pololu has an excellent line of motor controllers.

The magnetometer will not give accurate azimuth readings if not properly calibrated in the final installation.

Thank for the information about the motor controllers, so just about any DC motor controller would essentially work because deep down, these are big DC motors :stuck_out_tongue:

Would the magnetometer be a reliable instrument if i did go this route? Or should i look into having some sort of position sensor on the axle of the motor?

Thank for the information about the motor controllers, so just about any DC motor controller would essentially work because deep down, these are big DC motors

Yes, which means, of course, that you can NOT control the position where it stops very accurately.

Bite the bullet, buy a stepper motor and stepper motor driver.

Would the magnetometer be a reliable instrument if i did go this route?

No. Magnetic fields move. It is the shaft position that matters. Get the right kind of sensor - a rotary encoder - to know that.

Or should i look into having some sort of position sensor on the axle of the motor?

How many times do you need to be told?

You may also search for wiper motor servo mods, e.g. this movie.

Then arduino is using only servo library.


If you still want to use a 5883 magnetometer, a fixed large nearby magnet in its proximity would provide a stronger magnetic reference that is less influenced by nearby iron objects

Is it a yagi? The first strong wind is going to turn it into an interesting kinetic sculpture.

The worm drive in a windshield wiper motor normally cannot be reversed it will rather break than moved by wind.

blimpyway: The worm drive in a windshield wiper motor normally cannot be reversed it will rather break than moved by wind.

Then it will break. :)

It's a matter of leverage, he can use the thumb rule - if it doesn't break your thumb, it will not break the gear. Those gear motors break thumbs. The gear is designed to sustain several times the stalling torque of the motor, for fatigue reasons. They last millions of cycles.

Of course it all depends on how it's mounted and what size/shape antenna has, all we know is it weighs 5 pounds.

blimpyway: It's a matter of leverage, he can use the thumb rule - if it doesn't break your thumb, it will not break the gear. Those gear motors break thumbs.

Unfortunately, a yagi will not break under circumstances that would break your thumb. So yagi wins.

Tthe entire 4 antennae assembly is 5lbs. How big a 1lb antenna can be?

A 100 cm yagi in horizontal plane will be pushed with ~ 16N in a 30m/sec storm. Quite safe, even with 4 of them the torque will max around 30Nm. A 3m one in vertical plane will get 30-40 times more. Since we don't know what "yagis" are we talking about, how are they mounted, and where the rotation center is placed in relation with the wind pressure center, we don't know even if there-s any further gearing between motor and antenna, we have a useless conversation.

Ill just get a stepper motor haha. The yagi antennas are made from #8 solid copper wire, and wooden booms. They are not very heavy. I have used all of them and they all work pretty well.

Ill just bite the bullet and spend some money on steppers. But thanks for the input guys.