Display Degrees of rotation.

[aratti]

I am planing on using the encoder from a computer mouse

Old days mouse encoders are not suitable for your application, since they have very low resolution. they will have no more than 48 pulses per turn. Additionaly you will need two channels so that you will control also direction (I am sure you will need to turn CW and CCW your antenna)

You will need also a reference pulse that will be activated when direction is at 0 degree, so you can adjust possible error in the count.

You will need at least a 360 pulses per turn, yielding a resolution of 1 degree (I am not an expert in directional antenna but one degree seems to me not enough). With an ecoder at 360 pulses per turn two channels, using a technique called "quadrature" You could achieve a resolution of 1/4 of degree, that can be doubled with a mechanical transmission yielding two turns of the encoder per turn of the antenna.

Pic mcu can handle the encoder input and display the direction of your antenna on a LCD.

The hardware is not very difficult, apart the shielding of the signal cables, the software is also not very difficult but not for a beginner for sure!

Al.

[Bobw55]

I do not plan on using the pule disc from the mouse, just the encoder from a newer one. It will be driven via a gear that would provide about 3 rev per single rev of the antenna giving at least 1000 pulses. As far as a zero point, I was figuring on using a push button for that part. I would like the display to be accurate as possible even thought +- 5 degrees is close enough.
I am still planning all of this.

Bob

[cncmachineguy]

a good source for encoders is US Digital They are very resonable on pricing and also nice folks. I have been buying from them for about 10 years. They have a wide variety, so I am sure they have something you could use. As for cost, keep in mind what it will cost to scratch something together using an old mouse. You could make it work with 48 pulses per rev, but again, it depends on what you want to spend. I would want at least 1 degree per rev, so for that you would need a 7.5 to 1 mechanical gizmo to spin the mouse encoder 7.5 times faster then the antenna. (Lego's come to mind)

The encoders I have used from US digital all have TTL level outputs, directly readable by the PIC. I am not sure if you can expect a clean transmission from the roof to inside the house. If not, you could have a pic at the antenna send RS232 signals to the house, then read them with a puter of build a unit for inside to display the position.

[cncmachineguy]

This little unit looks pretty nice
It absolute so no need to store the position, 0-5V analog output, 20 mA draw. only $40!!

[Bobw55]

I think the sensor from the mouse will work. It is the disc that I have to change out. If I can elongate the motor shaft to accommodate the disk, I can have all the pulses I need. It will create the problem of having to figure out how many per one rev of the antenna. Not too much room in the housing accept under the motor. I have also thought about using the hall sensors that are inside a CD drive motor. For me, finding a way to get sensor information from the motor is the easy part. Selecting a PIC and LCD display will be the hard part..
Keep the ideas coming!!!

Bob

[Darrel Taylor]

Just a crazy thought ...

Is the rotor's motor AC or DC?

If it's DC, maybe you could count the commutator pulses from the motor current, and not need an encoder at all.

[Bobw55]

It is 2 phase AC. I thought about replacing it with a DC motor. It would be easier to have the display unit control the motor as well. This is a small TV antenna style rotator. Because the control unit uses TIME to allow for movement, the pointing accuracy can really vary, and you are mechanically locked into a max of 360 degrees of rotation. Once I figure out a digital display, I am going to remove the mechanical stop. I would like to under rotate by 90 degrees and rotate past 360 by 90 degrees (540 degrees total).

Bob

[aratti]

How much power do you pump into the antenna ?

Al.