Problem with VBox III Accuracy

[linuxman]

Well I am in the process of solving a problem that I have been having with the VBox III that I bought a short while ago.

I had noticed that many times when I would change satellites using the VBox III with my 10' Unimesh dish that I would have to adjust the position by a few counts to get the best signal.

I went up on the roof today and pulled the cover off my 24" Von Weise actuator to just take a look.

I got the model number which is a VW-24LC and called Von Weise in St. Clair, MO. I talked to a guy there who was very knowledgeable and told me how many counts per inch that my actuator was putting out. It turns out that it only puts out 24 counts per inch. That translates into a little over 400 counts in the entire travel of my actuator arm.

I never paid any attention to the total number of counts, and just assumed it was all up to par.

I asked about taking a magnet out of a junk actuator and putting them in, but they won't fit. He gave me the dimensions of the magnet I need, and said I should be able to find them in a craft or hobby store. He is sending me one, just in case.

The magnet holder on the 24LC holds two magnets, but they come from the factory with only one in place. I can double the counts by putting in the other magnet. That will make the positioning twice as accurate.

Sadly, that may account for the spun aluminum dish and the fiasco I had with it. If you remember, I was using an analog receiver to move the dish which made it even less accurate combined with a small number of counts, which may have caused me to mis-judge it's abilities, and an unfamiliar receiver for tuning purposes. That's a shame and one I won't soon forget.

But I pass this information along hoping that someone might find it useful.

I have found that most of these manufacturers are more than willing to help customers fix or solve their problems with equipment that may have been sold 10 or 15 years ago.

Von Weise is one of the good guys.

 

[gabshere]

i have the same problems i have to re-adjust probably every other time i sweep the arc. i didn't think the von weise folks were still in around. but my actuator on this 7 1/2 ft dish is a superjack 18 inch. ( i do have a 24 in von weise though) don't know how i would increase the accuracy on this actuator but i will be following your adjustments on your dish to see how it works.

 

[linuxman]

i didn't think the von weise folks were still in around.

Oh yeah they are still there in St. Clair MO. They are a Fasco Gear and Motor subsidiary. fasco.com

i have the same problems i have to re-adjust probably every other time i sweep the arc.

I have discovered during the past year and a half that I have been tuning C-Band dishes that there are two possiblities for this occurrence.

One is that the dish is not properly tuned which may have multiple sub-causes. Think of the sweet spot as a small circle on the center of the dish. If too high, you still get good SQ, but the width of the sweet spot is very narrow. If too low, the same thing. If just right, you get good SQ, and the width is wider which will allow for some inaccuracy when the dish comes to a stop.

The other is low count numbers. One pulse moves the dish too far one way, and vice-versa.

All of the above assumes there is no slop in the actuator, or mount assembly.

 

[iammike]

For what it's worth, I'm using a vbox II with a Von Weise 24" arm. I have the V76-5 model which is rated for 48 counts. I think I have something like 800 or 900 counts through the arc. I haven't had any accuracy issues and I've got pretty much everything from Intelsat 9 at 58 degrees to AMC7 at 137 degrees programmed into my VBox. I think you'll be very happy with your results once you upgrade your arm.

Mike

 

[gabshere]

Linuxman
This is only with your V-Box III right your V-Box II tracks fine ?? or did you try it ??
wonder if the g3000 ( GBOX) does a better job or if its just the sensor on the actuator.... or if its actually the V-Box III

someone mentioned that they discontinued the V-Box III and now have a V-Box V out

i suspect its actually the v-box III with a problem ( but thats me thinking ) and doubling up your count to be more accurate won't hurt ( but suspect it won't correct the problem).

Sadly, that may account for the spun aluminum dish and the fiasco I had with it. If you remember, I was using an analog receiver to move the dish which made it even less accurate combined with a small number of counts, which may have caused me to mis-judge it's abilities, and an unfamiliar receiver for tuning purposes. That's a shame and one I won't soon forget.

i think if the problem is v-box ( and you moved the dish with a regular analog receiver) then you would still get the same results . but i could be wrong about it.

I'm using a vbox II with a Von Weise 24" arm. I have the V76-5 model which is rated for 48 counts

thanks Mike , i think thats the same model actuator i have on my 10 ft dish. your using a V-Box II with good results.

 

[linuxman]

This is only with your V-Box III right your V-Box II tracks fine ?? or did you try it ??

Hey George,

This is only with the VBox III. I have not tried the VBox II on this dish.

i suspect its actually the v-box III with a problem ( but thats me thinking ) and doubling up your count to be more accurate won't hurt ( but suspect it won't correct the problem).

I'll know soon enough. I plan on putting the new magnet in this afternoon.

I think you'll be very happy with your results once you upgrade your arm.

Thanks Mike!

I certainly hope so.

I have two other Von Weise V76-5 actuators on other dishes and they work fine. I just wish I had noticed the low count number long before now.

Oh well another lesson learned.

 

[Anole]

maintaining accurate pulse count

Linuxman -

Technical Background (skip to * for the simple version):

I think when you were putting up an early BUD, probably one of your beloved BirdView, we talked about gear ratios, and sensor pulses.
We also talked about hall-effect sensors instead of reed switches, and I did some serious thinking.
By arranging two hall sensors at 90º, followed by the proper electronics, you could get four or maybe eight pulses per shaft revolution with ease.
I can't remember, but the number may have been 16, and easily doubled again with a multi-pole magnet.
(technical material)

So, I was reveling in all the accuracy one could attain, and wondering what the max pulse count was of the common Vboxes.?
Then, it dawned on me that the only way the box knows which way to count the pulses (up or down) was by which way it was powering the motor.
Although the electronics could probably extract a direction as well as pulse, the Vbox cannot accept direction, so you're screwed right there.


* Solution ?

The Vbox needs to ignore noise and discriminate against too-fast pulses.
Probably against pulses when the motor isn't powered, too.
If your Vbox is at fault at all , it might be simply that it's not filtering the pulse signal sufficiently.
If so, that we could fix.

Most likely, all the Vboxes are fine, and the only problem is 16 vs 32 counts, or 24 vs 48 counts, whichever applies.
Which is to say, more counts should help the accuracy problem.

 

[linuxman]

Most likely, all the Vboxes are fine, and the only problem is 16 vs 32 counts, or 24 vs 48 counts, whichever applies.
Which is to say, more counts should help the accuracy problem.

Hey Anole,

At this point, I don't think it is the VBox's fault.

I picked up some magnets (two different strengths) last evening at a hobby/craft store and following the instructions I got yesterday, gave them both a shot.

The instructions were to put the opposite polarity in the second magnet holder than the one already installed. One pushing the switch, and one pulling the switch.

After trying both strength magnets, I tried calling the guy again, and he returned my call, but I had stepped out for a bit and he told my son that he had sent their magnet out, so I didn't get to talk to him the rest of the day.

I don't know why he gave the instructions he did, but after thinking it over, the instructions didn't make any sense.

There is one magnet in there now. How does the switch get back after the magnet pulls it?
The answer is of course that it is spring loaded, and both magnets should pull as the single does now.

So I am waiting until the OEM magnet arrives (should be tomorrow) then I will install it with both magnets pulling on the switch.

One of the ones I bought would probably work fine, but is just installed backwards.

I think you are correct that more counts will give more accuracy.

 

[Anole]

confusing myself

Also, I'm talking pulses per revolution.
The motors are rated in pulses per inch!
edit: so if the screw is 24 threads per inch, then one pulse per turn would be 24 pulses per inch!

I'd need to see pictures of what you have and what you purpose.
Basically, the reed switch will close when either a N or S end of a magnet is close to it (in a simple world)
If the mechanism has a magnetic pathway built into it (possible but not likely for a 70's design), that could complicate the discussion.

So, if a simple N--S magnet were to rotate slowly near a reed switch, the switch should close twice per revolution of the shaft.
Once when the N end passed the switch, and once when the S end passed it.

However, if the magnet were offset to the edge of a disc which rotated near a magnet, then only one pulse would be delivered per rotation of the disc/shaft.
There, putting two magnets on the disc... (or four, if you had small magnets and a large disc), would double (quadruple) the number of pulses.

 

[linuxman]

If the mechanism has a magnetic pathway built into it (possible but not likely for a 70's design), that could complicate the discussion.

Actually this actuator is probably a 90s design. It is one of their later models.

The magnet holder is made of brass and is slid onto a gear that sits between the motor gear and the shaft gear.

The brass holder is between the magnet and sensor which sits on the outside of the housing.

Somehow it works as is with one magnet. The single magnet is pulling from the direction of the sensor. There must be something that returns the switch to be pulled again the next time around.

However, if the magnet were offset to the edge of a disc which rotated near a magnet, then only one pulse would be delivered per rotation of the disc/shaft.
There, putting two magnets on the disc... (or four, if you had small magnets and a large disc), would double (quadruple) the number of pulses.

I believe that putting the second magnet in place also pulling from the sensor will produce double the counts.

Right now it is 24 counts per inch of thread traveled.

That translates into 6 counts (pulses) between 91W and 93W. On all my other actuators it has always been 12 or 13 counts between those two satellites.

 

[gabshere]

Well Linuxman hopefully it will work ...then i will have to think things through and see if i can add a second switch to my actuator or what to get it up to par... photos would be nice of your motor adaptation.

if your situation works do you think adding a second sensor to my motor would in effect double the counting of the motor arm?? i would have to look at the motor and see if i can make it work .....

 

[linuxman]

if your situation works do you think adding a second sensor to my motor would in effect double the counting of the motor arm?? i would have to look at the motor and see if i can make it work .....

I'll take some pictures tomorrow when I open it back up.

I have been told by Caddata, Anole, and others including my neighbor across the street that adapting a slotted wheel of some kind and a new electronic sensor would be very simple to do.

My neighbors biggest concern was like Anole's above. How many counts can the VBox tolerate?

No one seems to know the answer.

Theoretically adding another sensor to your unit would work.

 

[gabshere]

My neighbors biggest concern was like Anole's above. How many counts can the VBox tolerate?

well the way it performs its just counting but my range now for counting goes from 800-200 so thats only 400 counts so if i double the effective counting of the arm it would come out to 800 within the 1000 counts of the unit before crossing positions..... correct??

Theoretically adding another sensor to your unit would work.

yeah thats what i thought so i will think about another sensor and how i would affix it to the unit. I suspect just wiring it into the same positions as the first sensor would work

I do consider this board to be the cutting edge for trying new things and like a final frontier for C-band . I know there are a couple other boards still but this is by far the best...

 

[linuxman]

but my range now for counting goes from 800-200

Is that an 800 on the East going to a 200 on the West crossing over the 000 mark on the LED?

If so, then it is only 400 counts.

I do consider this board to be the cutting edge for trying new things and like a final frontier for C-band . I know there are a couple other boards still but this is by far the best...

Absolutely!

 

[gabshere]

Is that an 800 on the East going to a 200 on the West crossing over the 000 mark on the LED?

If so, then it is only 400 counts.

yes the center of my arc is supposed to be 000 = 93W

 

[linuxman]

yes the center of my arc is supposed to be 000 = 93W

Then you are right, you are in the same predicament I am.

That's not enough counts to be very accurate when coming to a stop on a satellite.

Hopefully Anole or Caddata can help you set up something that will give you more counts, or contact SuperJack to see if they have a magnet wheel with more magnets. Most of the manufacturers will help you if they can.

 

[linuxman]

I got the magnet today from Von Weise, but it has rained all day and is raining now. The 3 or 4 inches of snow that was on the roof the last couple of days I have been up there is probably now matted down ice and slush. I think I will wait until tomorrow to put the magnet in.

Supposed to be 55F degrees and clear then.

 

[linuxman]

I got the magnet sent to me by Von Weise put in today, and it works as designed and effectively doubled the number of counts I was previously seeing.

It is now 13 counts between 91W and 93W.

I reset the VBox III and set the East and West limits and started programming the positions back in.

So far the accuracy problem seems to be solved. I will know more after I get all the positions programmed in and use it for a couple of days in the course of everyday viewing.

The Unimesh dish with the Co-Rotor (ADL designed probe) has turned the Unimesh into a signal sucking mamma for C and Ku.

I am able to get 43W to 148W with it, and the signal is fantastic all the way across the arc.

Here are the pics of the VW-24LC innards and the magnet holder. You will see a red circle where the sensor probe senses the magnets when you see the "open view". The last two pictures are of a V76-5 for those who have those actuators and want to experiment to add more counts.







My only regret is that I didn't figure this out and not taking the VBox II and Pansat to the roof for tuning the Solid Spun Aluminum dish.

But on the other hand, I might not have changed everything around and not have this Unimesh up.

The moral to this story is to pay attention to how many counts/pulses there are between each satellite. If there are only 6 counts, that's not enough for good accuracy.

Fred

 

[gabshere]

well great that it solved your problem ... and good to find out its not the v-box III now i just have to order another sensor and attempt to add it to my superjack 18" HD to double the count.

when i get this part and get it added i will post back the results.

Its also good to know that the von weise / falco folks are so helpful

thanks

EDIT : added again that i'm glad its not the v-box III with a problem, like i thought in my earlier post

 

[linuxman]

Hey George,

I hope you can get a few more counts out of yours too.

Fred