Polorotor master control

[Flinthill]

When slaving a Pansat 3500 to a DSR 922 what is the correct wiring scheme for control of the polorotor? Which of the two receivers will have the primary control, or can the control somehow be shared?

Thanks.

 

[drhydro]

Most people set it up so that the polarity is controlled by the 4dtv. There really is no way to share polarity control.

 

[Flinthill]

drhydro, thanks for the reply. I was hoping that there was some simple way of the two receivers' rotor control living happily together with no intervention, or if not that, possibly some type of interface box that each could work through.

I am no electronics person by any stretch but it seems to me that since the rotor servo works on a three wire arrangement with 1 (common) ground and the other two used for sending the clockwise pulse (1 wire) and the counter clockwise pulse (1 wire) that one could install a single diode in each line between the receivers and the servo motor. The diode would allow current to flow only one direction...toward the servo motor. This would allow the signal from one receiver to control the servo while simultaneously preventing the signal feeding back to the other receiver. Both receivers would have one diode in each of the "hot" wires to the servo. Of course, the diode used would need to be of high quality to prevent any leakage back to the other receiver, so to avoid any possiblity of negatively affecting the componets of the other.

Any thoughts on this idea?

 

[tofer]

If the (common) ground on both units is common, and there is no additive voltage stuff happening then I dont see why not exept for one thing. Will changing the polarity with one unit leave the other one in the dust , not knowing the polarity has changed and assuming it is the same.

 

[Flinthill]

Your observation is quite valid. I believe a diode could also be put in the "common" line on both receivers to further insure protection...I'm not certain what effect this will have on the operation though, but an idea nontheless just to see if it will have any negative effect.

I think it is likely that if the polarity has been changed from where a receiver expects it to be, then that receiver will need to be moved to another transponder to reset the polarity. It seems that would be a very small price to pay for such a large increase in convenience. I have trouble imagining having to use the 922 to change the polarity for each transponder I want to view on the FTA receiver.

 

[kelleyga]

.

 

[drhydro]

If the (common) ground on both units is common, and there is no additive voltage stuff happening then I dont see why not exept for one thing. Will changing the polarity with one unit leave the other one in the dust , not knowing the polarity has changed and assuming it is the same.

my thoughts exactly, i have thought of having both receivers able to control polarity, but i cant figure out a way for both of them to coexist

 

[orthoclipse]

I use a DPDT (double pole, double throw) switch with a common ground to swap control between 2 receivers. I have looked at the pulses outputted by Pansat and Echostar receivers on an oscilloscope, and they both behaved very differently. I don't think it is possible to have 2 receivers connected simultaneously.


Polarotor specs from rec.video.satellite
Polarotor Servo Info.
---------------------
Supply requirements:
Voltage: Min 5V Max 6V
Current: 550 mA max.

Pulse control signal amplitude:
300 mV <= Low <= 600 mV
3.0 V <= High <= Supply

Pulse control signal period:
min 16 mS, max 21 mS

Pulse width controls probe position
700 uS minimum
800 uS +90 degrees
1150 uS +45 "
1500 uS 0 "
1850 uS -45 "
2200 uS -90 "
2300 uS maximum


Jitter < 2 uS




Pulse Shutdown.

To position the servo motor the pulse signal must be applied
for a minimum of 5 seconds. After that the signal can be
shut off taking care that the last pulse is not cut short.
This method is used by some IRD designs to avoid servo motor
hunting once it has arrived at the desired position.
The Sierra III for example sends a burst of pulses only
every 5 secs once the intial long burst has been sent to
postion the servo

 

[AntAltMike]

The three wire polarizer controls use a pulse train and the receiver responds to feedback from the polarizer motor. You need to replace your feedhorn with a modern, dual LNB so that the polarity can be electronically, independently switched.

If you call SatVision or some other dealer (are there any others?) then they can sell you some parts to do what you need. Expect to pay a hundred bucks or so.

 

[Flinthill]

I didn't know there was feedback from the servo motor to the receiver. Is the feedback sent back to the receiver on the same wire the original signal was sent to the servo?..or on the other wire? Additionally, it has been my understanding that the rotor moves in full 90 degree movements. Is this correct or does it move in small increments?

If indeed there is a feedback loop involved then my idea of using a diode in each "feed" wire to the servo will not work.

Orthoclipse: the use of a manual switch is by far the simplist and probably the most rewarding of any idea I have heard of.

I am using a Chaparral II+ with Norsat 8215 and 4206a LNBs.

I had originally planned to do the experimentation today but the Pansat replacement for the original unit came in bad, just like the first one. Also, UPS showed up today with the 922 and the box had been destroyed in shipment. The 922 was laid out bare for the world to see. It's been one of those days!!!

 

[AntAltMike]

The rotor motor responds in small increments. They typically have at least 180 degrees of range.

The company that makes SatLook (EmitorAB)also makes a product called SatSet that has a mechanical polarizer controller. It sells for about $100. It is controlled by a potentiometer.

When I said the polarizor motor sends feedback to the controller, I was relying on what I had read several years ago when I was contemplating making my own portable mover to use when servicing C-band disheds in the field, but since I found and bought a SatSet, I never pursued the project further and didn't actualy confirm the principles of the polarizer's operation.

But as I mentioned in my initial response, you should be able to retrofit the feedhorn so as to be able to have it simultaneously supply both polarities, either with an electronic 13v/18. dual LNBF or with a more conventionaldual Ku feed assembly (much more expensive, but probably necessary if you need to keep C-band) and a multiswitch.

 

[Flinthill]

I want to keep C band so I guess I am committed to locating one of the SatSet devices. I checked out SkyVision and talked to another sat equipment dealer but without any luck.

I did a search on the net to find the Emitor AB company in Sweden. They didn't have the item listed in their "products" area and have sent them an email asking if they have such a device.

Do you recall where you bought your SatSet?

 

[AntAltMike]

I think I bought it from Perfect 10.

I don't understand your needs. The Sat Set has to be somewhere, just like each receiver does. It can do what one receiver does. Buy a Bullseye dual C dual Ku feedhorn, and then you won't need a rotator.

EmitorAB has people with cool names, like Lars and Hans and Sven.

 

[Flinthill]

Before the polarotor control issue surfaced I had just purchased and installed a new Chaparral II+ feedhorn and Norsat LNBS. I am hip deep into the this feedhorn configuration and cannot change direction. I sent an email to Sven yesterday but don't have a reply. I'll check out Perfect 10. Thanks for your information.