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Atlas mount cant get enough power from battery

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#26 SpaceFreak131

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Posted 21 February 2013 - 10:14 PM

I tried manually holding the cable in with a good amount of pressure, didn't help.

Like the people have been saying, its probably a battery thing. Each slew takes about 20 seconds. Those car jump starters are only made to pump out current for a second. I'm thinking that maybe it can't sustain 2.5 Amps continuously. When I get a more reliable, high amperage power supply I'll try again.

#27 SkipW

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Posted 21 February 2013 - 11:44 PM

They're only designed to pump out the huge current necessary to start a car for a few seconds at a time. They'll pump out the small current needed to run a mount for hours and hours.

17 Amp-hours means, in principle, it can supply 1 Amp for 17 hours, 2 Amps for 8.5 hours, 17 Amps for 1 hour, 170 Amps for 1/10 hour, etc. Of course, it's not even close to that linear (and can't really deliver anywhere near 170 A at all), but that's the basic idea.

Jump start power packs work fine to power 12V telescope mounts in most cases. I'd suggest using an ohmmeter to measure the resistance of the cable assembly as a start. I would think it should measure less than one Ohm end-to-end for each conductor. The 25-foot spaghetti-thin DC cable that came with my CG-5 had several Ohms per conductor and didn't work worth a damn because as soon as you tried to draw, say, one Amp, about 10 Volts would be lost in the cable and the mount simply shut down because the voltage at its end of the cable was too low.

#28 Garry

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Posted 21 February 2013 - 11:52 PM

The mount might have another problem other than the power supply.
If you are well balanced,then at 2:05min and after the grinding noise
could mean too tight a mesh. A tight mesh alone can contribute to a
flashing red led.

Also you can read voltage directly from the hand controller from Utilities,
Show Information.

#29 SpaceFreak131

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Posted 22 February 2013 - 06:20 AM

The resistance is so small on the wire that I made, that my ohm meter doesn't even register it out to two decimal places.

What exactly is a tight mesh? Also, I've been checking the voltage in the handset, it usually says 11.7 to 11.9. Although if you check the voltage directly at the battery terminals, it says ~12.5 volts.

#30 RTLR 12

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Posted 22 February 2013 - 06:35 AM

11.7 volts is not enough volts to run the mount. You have a voltage supply problem. Either the battery is no good, or not charged, or you have too much resitance in the power cord, or you have a bad connection. As most have tried to tell you here the problem is NOT with the mount. A good 12 volt power supply should supply 12.7 to 12.9 volts at the mount.

Stan

#31 SpaceFreak131

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Posted 22 February 2013 - 07:26 AM

I'm gonna check that out. I tested the unloaded voltage, which was ~12.5, but when I get a chance, I'm gonna throw a 1K resistor in, and see how the voltage behaves.

I'm also going to fully charge the battery, even though it's currently near 100% according to the meter on it.

I'm also going to see about borrowing another professional grade power supply. This time one that can supply the full amperage at 12V.

#32 RTLR 12

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Posted 22 February 2013 - 07:55 AM

12.5 volts is only about 75% charge. 11.7v/11.9v is fully discharged. Measure the voltage when the battery has been charging after 5 minutes. If the voltage is close to the high 14v to the 15v range, the battery is no good. After charging the battery, let it sit for a few hours and then measure the voltage. 12.7 to 12.9 is a fully charged battery.

Stan

#33 FaronD

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Posted 22 February 2013 - 09:49 PM

It seems like something is too tight. Just listen to the motor stalling (not gear clutches slipping) near the end of the video. That grinding/clicking sound is from the motor stalling not due to voltage but resistance to movement. However, this will cause the voltage to drop because it is over amping. I heard that sound a couple of times. Once the ota touched the mount and there was that grinding kind of noise that I hear in the video, only constant. I noticed it again when I tightened the gear mesh too much while making adjustments. Which axis was moving at the end of the video? I would definitely check for binding on that axis. If the problem was low voltage I don't think the motor would slip/stall, the slews would just slow down. Perhaps it could even be a motor bearing??

Faron

#34 SKYGZR

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Posted 22 February 2013 - 10:04 PM

[quote name="WillCarney"]I purchased a deep cycle marine battery and a ac-dc inverter. For my Atlas I use the Orion AC adapter and plug into the inverter which attaches to the marine battery[quote]


The mount runs on 12V, you don't need an inverter, or the adapter. Attach directly to the battery. The inverter/12v adapter will draw down the battery way faster than just running the mount directly.

I use a 12V scooter battery..expensive, yet lighter than a full size deep cycle. The full size's are used with an inverter to power the laptops.

#35 SpaceFreak131

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Posted 22 February 2013 - 10:42 PM

Faron, I noticed that the declination axis is the one with the problem. And like you, it runs well without the OTA on it. I have everything balanced also.

And I fully charged my battery. The power light no longer goes out, and the voltage according to the mount is 12.5V (unloaded battery voltage is 13.4V). I verified this with a voltmeter. Even at full speed slew, the voltage never dips below 12.5V.

What do you suggest I do? I'm not the most mechanically inclined person, so I would appreciate any help.

#36 SpaceFreak131

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Posted 22 February 2013 - 11:46 PM

Nope, now it wont slew the dec axis under ANY load, telescope or not.

#37 EFT

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Posted 23 February 2013 - 12:11 AM

I went back and watched the video again and I agree that it sounds like the stepper motor is skipping near the end of the slew. Is there a scope on the mount? I can't tell from the video. How well is the mount balanced? Can you balance the mount well or is the axis too stiff to balance?

I'm just trying to get a handle on exact what the problem is that you are having. It sounds like the power issue may be solved, but there is something else going on.

#38 SKYGZR

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Posted 23 February 2013 - 02:40 AM

I've had "stalls" before on my mounts. the leading cause (that I've found) is that the motor(s) mounting screws (under the cover where the power/guide port plugs in), are overly tightened/misalinged.

One has to remove the four small screws that attach that cover to the mount, then using a long blade phillips head screw driver, loosen the motor mounting screws a bit, wobble the motor assembly up/down -side to side, and by feel, engage the gears "snug".

Once that's done, then "loosley" tighten the screws, "snug" but not overly tight.

If one is not mechanically inclined, this may be a challenge.

#39 Hilmi

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Posted 23 February 2013 - 04:52 AM

I don't have an Atlas, but to me from the first post in this topic it sounded like a motor stall.

#40 FaronD

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Posted 23 February 2013 - 08:18 AM

The first thing I would try is loosening the collar that is at the base of the Dec. That's the same collar that the counterweight shaft lock is attached to. There are grub screws in there, loosen them and turn the collar CCwise a half a turn. If that doesn't help turn a little more. The problem could also be that the gear mesh is too tight as I mentioned earlier. There are tons of articles out there on the procedure. It's time to become mechanically inclined. Does the Dec swing freely with the clutches unlocked or does it seem really tight?


Faron




quote]Faron, I noticed that the declination axis is the one with the problem. And like you, it runs well without the OTA on it. I have everything balanced also.

And I fully charged my battery. The power light no longer goes out, and the voltage according to the mount is 12.5V (unloaded battery voltage is 13.4V). I verified this with a voltmeter. Even at full speed slew, the voltage never dips below 12.5V.

What do you suggest I do? I'm not the most mechanically inclined person, so I would appreciate any help. [/quote]

#41 SpaceFreak131

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Posted 23 February 2013 - 01:16 PM

I FIXED IT. Like Faron suggested, the retaining cap for the counterweight bar was too tight. I loosened it a bit. Then I did a torture test. I ran the declination axis for about a minute which is a full rotation or two and only got 1 or 2 clicks. I loosened it just a touch more, and it was completely normal. No clicks, ran it for another 2 rotations.

Then I loaded it down with my telescopes and counterweights, ran the telescope around a full declination spin, and worked perfectly.

Thank you all so much for all your help, I really, really appreciate it.






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