Re: Hanging case for GTOCP4?


Roland Christen
 


Kinda sounds like true class A power amplifier operation in my Hi-Fi hobby.  The output devices are always "on", at full current.  They run at their hottest with no signal and need a ton of heat sinks and you never enclose them.
I think you are mixing apples and oranges. Massive heatsinks are not required on our CP controllers.

Microstepper servos need current to hold position, otherwise the rotor falls back to one of the magnetic positions. All AC servo motors have this requirement. DC servos do not need to hold position and current falls to zero when not moving. Dc servos also have large gear reductions so they can operate at very low current levels and still produce plenty of torque at the worm shaft. Typical gear reduction of a Dc servo is around 60:1, whereas AC servos such as used on the Mach2 have reduction ratio of 2:1 or thereabouts.

Dc servos require very expensive gearboxes and expensive DC servomotors, otherwise the periodic error gets ragged and massive. They also make audible noise that people don't like. For the Mach2 we decided to use AC servos with belt drive so that we could apply the savings to add the very expensive Renishaw absolute encoders. With DC, the cost would have put us out of contention with competitive mounts. Plus people would have ragged about the slewing noise.

Rolando


-----Original Message-----
From: Jeff B <mnebula946@...>
To: main@ap-gto.groups.io
Sent: Sun, Jan 3, 2021 12:04 pm
Subject: Re: [ap-gto] Hanging case for GTOCP4?

Kinda sounds like true class A power amplifier operation in my Hi-Fi hobby.  The output devices are always "on", at full current.  They run at their hottest with no signal and need a ton of heat sinks and you never enclose them.

Ignorant but curious, since absolute encoders know where they are all the time, can a model be built by manually pointing the scope, without any goto commands?

Jeff

On Sun, Jan 3, 2021 at 12:23 PM Roland Christen via groups.io <chris1011=aol.com@groups.io> wrote:
On the CP5 controllers I would advise against putting them inside a cloth bag. The CP3 and CP4 are ok because they do not produce very much current for the two servo motors under normal tracking conditions. The CP5 sends full current to both stepper servos all the time, even when they are not moving, so the drivers are at full power and produce more heat. The case dissipates the heat to the surrounding air just fine, but if they are inside a cloth bag, they will not have any air circulation.

Roland Christen
Astro-Physics Inc.


-----Original Message-----
From: Dale Ghent <daleg@...>
To: main@ap-gto.groups.io
Sent: Sun, Jan 3, 2021 10:58 am
Subject: Re: [ap-gto] Hanging case for GTOCP4?

With the mounting bracket, you only have to losen two thumb screws and tip the unit forward to remove it, and the opposite to install it into the bracket. It’s quite quick to do and doesn’t require any tools. The thumb screws are similar to if not the same as the ones which secure the sliding access panels on your Mach1. 

/dale

On Jan 3, 2021, at 10:46, Patrick Spencer <patrick.spencer2@...> wrote:

Hi everyone,

I recently upgraded from a CP3 to a CP4 for my Mach1. The only thing I miss about the CP3 is the neat hanging case, which made it easy to "grab and go" and allowed me to hang the controller from a knob at the base of the mount. Unfortunately, the CP4 is too large to fit in the CP3 case. I know there's a mounting bracket option, but I like being able to quickly disconnect the control box and take it inside when I'm finished imaging.

There are a lot of clever folks in this group, so I was wondering if anyone has come up with a similar hanging pouch/bag solution for the CP4?

Thanks,

Patrick Spencer

--
Roland Christen
Astro-Physics

--
Roland Christen
Astro-Physics

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