motor loses its mind when powered down

[Jim S.]

I have a Sadoun PowerTech DG-280 motor that's developed a weird problem. Every time I start my receiver, I have to tell the motor to go to reference. If I don't, it seems to have no idea where it is. Most of the time, trying to go to any satellite (via USALS; I haven't tried 1.2 because I don't have it set for any birds) will result in the motor going to the east hard limit -- even if the satellite is west of where the motor started. I tried the reset procedure in the manual and at first I thought it worked, because the next attempt to go west went west, but even though it didn't go all the way to the limit it still didn't stop where it was supposed to stop. Another weird thing I found is that if I attempt to move the motor with the manual controls while it's at the east limit, it won't even go back to 0, stopping at about 10 degrees instead.

The whole thing has got me stumped. The last time I had a motor problem (bad relay), it would go all the way in one direction when trying to move either direction, but since it was a mechanical hardware problem, there was no way to get it working correctly. This time, if I give the go to reference command, it works fine again for as long as I don't shut the receiver off. (And I've tested it with another receiver to make sure that it wasn't the receiver going buggy.)

I don't feel like taking the dish down and remounting it in the winter, so I'm not buying a new motor yet. I wish I knew if there was some way to fix this one though. For now, I guess I'm just going to have to send it to 0 every time I want to use the dish. Either that or leave the receiver on all the time.

 

[xtgold]

as a test I would aim for a sat with usals then switch to diseqc 1.2 and save the position.Do it for a few sats then save the positions.Then cycle power on the receiver to see if the dish behaves.You may end up using diseqc 1.2 instead of usals.

 

[Jim S.]

I tried that today, it still doesn't go to the correct positions. No matter what I do, I have to send it to the reference position every time I power on the receiver, or it doesn't know where it is.

Til I decide what do do with the motor, I may try leaving my receiver in standby mode instead of powering down all the way. It seems to only shut down the video output, the USB ports stay powered up, so I'm assuming it may leave the power to the dish on too. But I don't like leaving the hard drive powered up all the time, maybe I'll have to unplug it.

 

[AcWxRadar]

JimS,

Which receiver are you using to control this motor? This could be a receiver problem since there is nothing stored in the motor when using USALS. The motor positioning is all calculated from the lat/long coordinates of the site and the orbital position of the satellite selected, all of which are stored in the receiver. Therefore, as a first step, I would test a different receiver to verify if the trouble remains with the motor or follows the receiver.

I have read others report that their H-H motors were losing the home or zero position reference, but I have never experienced any trouble with the DG- series motors. I do believe that once the motor reads or detects the home position sensor, that the rest of the motor movement is determined by pulse counts, like reading an optical encoder wheel. If the circuitry which records these pulse counts isn't maintaining the count when powered off, then this would make sense as the motor would "wake up" not knowing where it is.

So, possibly there is a battery backed up RAM (BBRAM) within the motor that has failed. Most BBRAMs that I have been exposed to have a 7 year life expectancy. I am not certain of this, I am just taking a SWAG at it.

RADAR

 

[Jim S.]

I had the Amiko Alien 2 hooked up when the problem started. Since I had a memorable motor freakout with that receiver when it was new (I think it was a corrupted satellite list), I grabbed my old Openbox out of the closet and hooked it up. The problem persisted.

Later tonight I'll pull my old DG-280 circuit board out of the closet and see if I can find a battery or a supercap on it, although I don't remember noticing any such thing. That board has a stuck relay, and since it's a micro-relay that I couldn't figure out how to crack open nor find a replacement for, I just bought a new board from Sadoun for about half the price of a new motor. The original board only lasted about a year and a half -- about the amount of time the new one lasted before this new problem showed up...

 

[Jim S.]

I looked at the old board. No battery, and the largest capacitors were 1000 mic. There was one component wrapped in black rubber with no ID, but the silkscreen says L1 so I have to assume it's an inductor.

 

[AcWxRadar]

Jim,

I am not certain of how this motor retains that memory. But, the BBRAM IC that i spoke of looks like a typical IC, except it is "fatter" (taller and wider). The lithium battery cell is actually built into the IC so there wouldn't be a separate battery like a coin cell type on the board. I really am grasping at straws on that idea as I don't know how the memory is retained. I honestly would think that they would use some sort of EEPROM instead, but I would think that an EEPROM would be rare to fail so soon, so that is why I questioned if they might have incorporated a BBRAM. It was a thought anyhow.

RADAR