Counts per degree?

[nhulst]

Is there any expected range for the number of counts per degree on your actuator? My setup is a Sadoun 6' dish/polar mount with a Venture Maxi, and I'm getting about 5 counts per degree, or about 10 counts center-to-center between satellites. This is proving to be a little bit tricky for repeatability. Making it more difficult is the fact that the analog receiver I bought occasionally decides all on its own to drive the dish several counts past where I asked it to stop. Grrr.

If you know offhand, please post your dish, actuator, and counts per degree. I'm interested to compare.

One of these days, I'll get all the pictures from my install posted...

 

[Magic Static]

It's all about geometry. The farther away from the center of the dish you attach the end of the actuator the more counts per degree. With a linear actuator, the spec is counts per inch of travel of the actuator. Some actuators do have a higher count rate than others. The WSI 6' special and PMA24 actuator I had at one time did about 9 - 10 counts per degree.

 

[T4Runner]

This is a tough question to answer because it can be so different on different actuators and even on the same actuator on different parts of the arc. The older and more expensive actuators are more accurate because they have more counts/clicks. Lots of threads on this one...

http://www.satelliteguys.us/threads...-quot-on-controller?highlight=Actuator+count?

my super jack II is around 5-7 clicks per two degrees between satellites.

 

[nhulst]

Whoops, sorry I failed to search first. I'll go take a look. Sounds like my result is not way out of line, anyway.

 

[Lone Gunman]

All this and remember that the further out you go with a linear actuator, the LESS the count will be per degree!! On my Unimesh system I have only 6 counts between 43W and 45W but on the other end, I have 18 counts between 133W and 135W.

 

[wbarrett]

One comment I will add in addition to the ones about where you are in the arc and the counts per inch all making a difference.

My C-band dish is a good 250 foot run from my receiver. I was having same issue with positions slightly changing and mostly as you going too far which I determined was due to missing pulses. The missing pulses meant the dish mover was counting too few and moving the dish too far. I put an in-line signal amplifier and while it did not make much of a difference on signal quality, I did find that I no longer was missing pulses and having antenna pointing errors.

===
Bill

 

[SatelliteAV]

A coax inline amp?

Wouldn't make sense as to making any improvement as the pulse counts are not carried on the coax. Tried removing the inline amp to verify?

I am almost completed with development on a new motor control box that provides 50hz resolution / accuracy. Will be for sale before Christmas....

Add all the magnets that you want! Fifty pulses per second is capable of producing extremely accurate aiming.

 

[gpflepsen]

A coax inline amp?

Wouldn't make sense as to making any improvement as the pulse counts are not carried on the coax. Tried removing the inline amp to verify?

I am almost completed with development on a new motor control box that provides 50hz resolution / accuracy. Will be for sale before Christmas....

Add all the magnets that you want! Fifty pulses per second is capable of producing extremely accurate aiming.

Are you including a control routine to prevent overshoot of the position setpoint?

 

[SatelliteAV]

Are you including a control routine to prevent overshoot of the position setpoint?

How would that work? A saved position is a saved position. There is a problem with either the controller or the dish hardware if the motor doesn't return to the exact saved position.

The new unit ramps speed in and out of moves to reduce wear and tear on the actuator and dish hardware.

 

[gpflepsen]

How would that work? A saved position is a saved position. There is a problem with either the controller or the dish hardware if the motor doesn't return to the exact saved position.

The new unit ramps speed in and out of moves to reduce wear and tear on the actuator and dish hardware.

Speed ramps would be a control scheme. Anything to prevent overshoot on a positioner with that high of resolution would be a required part of the design. I was curious how you were handling it.

 

[Magic Static]

Well I got a sensor just waiting for that controller SatelliteAV, and I will put it to task

 

[Anole]

Finally

With all the cheap technology at hand, it's fulfilling to see some of it applied to this Stonehenge problem! :up

 

[FaT Air]

Making it more difficult is the fact that the analog receiver I bought occasionally decides all on its own to drive the dish several counts past where I asked it to stop.

Disconnect the motor wires from the mover. actuate the mover, then when stopped, ohm the motor terminals. Repeat many times. There has to be a dead short every time. If not, overshoot is certainly guaranteed. The short acts as a heavy load on the generator(which was the motor until the applied power disappeared, and brakes it.
If you see something other than a dead short(even a couple of ohms) Clean the relay contacts or replace the relays.

 

[SatelliteAV]

Overshooting should not be a problem with any controller or actuator. A count is a count. If the motor overshoots, the controller would know that the count is not correct and move the motor to the correct count position.

Been in C-band for 30+ years and worked hundreds of systems. As long as the hardware or cabling is not defective, there are no missing counts. Never have encountered an overshoot when gear was working properly.