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G11 supply voltage

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#1 hickeydp

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Posted 16 May 2011 - 05:58 AM

I'm running my G11 on a regulated 13.8v 4A power supply. Someone told me a while ago that the mount ran better on 18v. I don't have a great deal of faith in the person who told me this however I do have a 12-18v DC-DC converter rated at 2.7A.

As the mount recommends a 3A supply I'm thinking I'm a little underrated but should be fine. My question is, is there any advantage to running the mount at 18v? My honest guess is no, it should make no difference at all but thought I'd ask.

#2 nemo129

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Posted 16 May 2011 - 07:13 AM

Hi Damien,

I am running my G11 off of 13.8VDC @ 10A power supply with no issues. I noticed that Losmandy sells a 13.8VDC @ 5Amps on their website specifically for Gemini powered mounts. ( I actually think it is a re-branded Pyramid PS9KX which can be had for about $30USD on Amazon). As to the need for 18 volts, I think that is simply the published high end of what will work. You could post the question in the Yahoo Gemini group and maybe René could provide a better answer.

#3 jmiele

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Posted 16 May 2011 - 09:18 AM

AP sells the Pyramid 5Amp 13.8 as well as a 15 volt 10Amp.. Joe

#4 Eddgie

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Posted 16 May 2011 - 09:25 AM

I am not sure at all how it would "Run Better" with more voltage.

The motors are controlled by the electronics, and they provide the driving voltage and current (Stepper Motors on the standard G11, and the controller provides discreet pulses to drive them at the desired rate).

There would be ABSOLUTLY no "Improvement" in their ability to drive the scope regardless of what voltage you put into the controller.

In fact, I personally believe that the potential to damage things are far more likley than the potential to "Improve" things.

If your mount functions well on the supply you are using today, then there is not a thing to be gained by increasing the voltage.

Regards.

#5 jmiele

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Posted 16 May 2011 - 09:55 AM

"I am not sure at all how it would "Run Better" with more voltage."

AP recommends cold weather users go with higher voltage supplies. Also for bigger mounts with higher loads. Cold weather and heavy loads result in a drop in voltage output from the power supply. Larger units with bigger capacitors can maintain spec more closely. Spec as in AP required voltages. The 15 volt unit will drop voltage under strain but still within spec for the using device.

Motor stuttering has been reported at high slew speeds in cold weather when under voltage. A 12 volt car battery is 13.8 volts (close too it) only when fully charged. Under strain and as it is drained the voltage drops quickly. Toward the end of it's charge it will be around 11.5 volts.

Last, as these are cheap low quality supplies the regulator sections quality drops quickly as price goes down. Normal home voltage (US) of 110v in NOT always 110v. It will vary from 120-130 all the way down to below 100v throughout the day as strain is put on the electric companies infrastructure. This also contributes to the 13.8 spec'd voltage starting out lower.

For the best, most consistent performance using LARGE 12 (13.8) volt Gel cell deep-cycle batteries is the way to go IMO.

Does you car starter sound the same as you try to start you car when the battery is dying? Does the starter motor sound funny/different when starting it in extreme cold weather? High capacity well regulated power is our best bet..

Joe

#6 skybsd

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Posted 16 May 2011 - 11:32 AM

Hello,

I am not sure at all how it would "Run Better" with more voltage.

The motors are controlled by the electronics, and they provide the driving voltage and current (Stepper Motors on the standard G11, and the controller provides discreet pulses to drive them at the desired rate).

There would be ABSOLUTLY no "Improvement" in their ability to drive the scope regardless of what voltage you put into the controller.

In fact, I personally believe that the potential to damage things are far more likley than the potential to "Improve" things.

If your mount functions well on the supply you are using today, then there is not a thing to be gained by increasing the voltage.

Regards.


On the contrary.., on a phone call with Losmandy, they (well.., you know who I mean) advised me that cold weather operation as well as loads at the top end of the G11's payload capacity are the reasons where they recommend running the mount on 18v supply - particularly where slewing at speed is concerned.

Regards,

skybsd

#7 skybsd

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Posted 16 May 2011 - 11:36 AM

I'm running my G11 on a regulated 13.8v 4A power supply. Someone told me a while ago that the mount ran better on 18v. I don't have a great deal of faith in the person who told me this however I do have a 12-18v DC-DC converter rated at 2.7A.

As the mount recommends a 3A supply I'm thinking I'm a little underrated but should be fine. My question is, is there any advantage to running the mount at 18v? My honest guess is no, it should make no difference at all but thought I'd ask.


Hello Damien,
Its fine to run the mount on 18v - though you'd want 5A minimum. I powered my former G11-Gemini via a 13.8V 7A regulated PSU.

What are your reasons for wanting to do this anyways?

Regards,

skybsd

Youd

#8 mistyridge

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Posted 16 May 2011 - 11:37 AM

I am using a Pyramid ps-9KX. You can buy them on Amazon for about $30.

#9 Billydee

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Posted 16 May 2011 - 01:25 PM

Here is a link to Ritz camera. They sell Pyramid PSs at the lowest prices. 5 amp is $25.94 and the 10 amp is $47.94. They also have a 3 amp without car adapter plug for $19.94.

http://www.ritzcamer...upply&x=40&y=14

I suggest the 10 amp because each motor in the G-11 can pull 2.6 amps at 12 volts when slewing both motors can run giving you a 5.2 amp draw (the 5 amp PS does allow for a 7 amp short term peak draw). The 10 amp PS allows a safer buffer and is much heavier in build.

The G-11 has always run on 12 to 18 volts. It runs much better on 18 volts. It does not slow under heavy loads at 18 volts. Why? because the watts to run your motors is the same at 12 volts as it is at 18 volts. What changes? is that as the volts go up the needed amps go down to get that same watts.

12.0 volts the amp draw can be 5.6 amps

13.8 volts the amp draw can be 4.9 amps

18.0 volts the amp draw can be 3.7 amps

Put a meter on your PS and you will see the voltage drop as the amp draw increases. The higher the voltage the less it reacts to the amp difference. The higher the PS amp is rated the better it can handle a load increase.

You might note that your 2.7 amp DC-DC converter can not handle the 3.7 amp draw at 18 volts.

Luck, Bill

#10 skybsd

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Posted 16 May 2011 - 03:01 PM

"You might note that your 2.7 amp DC-DC converter can not handle the 3.7 amp draw at 18 volts."

Pretty much matches the guidance I got from Losmandy to ensure a PSU rated to 5A minimum when considering supplying 18v to the mount.

Regards,

skybsd

#11 Jovian

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Posted 17 May 2011 - 11:22 AM

Kendrick makes a very nice inverter/rectifier that is intended to run a Losmandy mount. Input: 12VDC, Output 18VDC, fused at 7A. A power cord is available that is specific for the G11. I have one (although I haven't yet assembled my G11). The build quality seems very solid.

#12 averen

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Posted 17 May 2011 - 10:30 PM

I packed up a variable power supply that outputs 18V @ 6A for about $20 at my local electronics store.

However I rarely run my G11 on 18V. I didn't notice any difference when running it at a higher voltage. However I'm a ways away from the max capacity of the mount and it doesn't get cold here in Texas! 12V makes more sense to me since I generally have to use batteries. Up converting the 12V to 18V takes an additional toll on my batteries.

Jared

#13 ZRX-Steve

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Posted 17 May 2011 - 11:09 PM

I have the Kendrick 12VDC to 18VDC inverter. The accessory plug is smaller than my other devices with accessory plugs. On the Kendrick, there are two conductors, I tip and the side conductor. My other accessory plugs have 2 or 4 side conductors with make for a tighter fit in the plug socket. The net result is that it's always falling out.

Kendrick recommended bending the side conductor out to make it fit which didn't help much. Kendrick is a Canadian company with a good reputation. I don't know, maybe there is a different size standard in Canada. In any case, I'm not inclined to use it very often and use a Pyramid 13.8 vdc power supply most often with good results. In fact, I can tell no difference in motor slewing or motor sound between the 13.8v, and the 18v Kendrick Inverter.

#14 hickeydp

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Posted 19 May 2011 - 01:11 PM

Thanks as always for your comments. I've not had a chance to read them since I posted as things have been a bit hectic here so only catching up now.

To answer your question Skybsd, the original dealer put the idea in my head. He maintained that the mount was more responsive when running at 18v. I know you know who I'm talking about and appreciate that I would lend no credibility to anything he would have to say. It was rattling around in my head and I thought I'd ask, as even though I expected it would have no effect, maybe there was something I was missing.

From what I'm reading it confirms what I had suspected that the 18v really only ensures there is no drop below the minimum voltage for given loads and weather conditions.

However what has come as news is the rating required for the mount. I thought I was safe at 4 amps from a very well regulated and fairly expensive switch mode power supply. Seems I may need to beef that up. Had no idea it could pull over 5 amps when slewing both motors.






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