EQ6-R current draw

[Tomatobro]

For the design of some special hardware I had cause to measure the current draw of a EQ6-R mount under various operational conditions.

What surprised me was that after connection the highest current draw (other than when slewing) was when the mount was parked. The current measurements were taken in sequence of On, Connected, Tracking (Sidereal), Parked, Unparked, Slew, Tracking and Parked again.

I posted this data as somebody might find it useful

 

EQ6-R.odc

[fifeskies]

can you post a screengrab of the table as a jpeg

the download file seems to have some issues with me.

 

thanks

[Rusted]

My guess is that parking needs to hold the stepper motors still.
So locking against rotation draws the most current.

I used to monitor the current drawn from the PS on my AWR GOTO system.
The supplied 12V PS had died within 2 years.

So I replaced it with a meaty Meanwell PSU on the advice of others here.
A 40mm fan cools the PSU in its transparent lunch box in which it dwells.

[Rusted]

2 hours ago, fifeskies said:

can you post a screengrab of the table as a jpeg

the download file seems to have some issues with me.

thanks

MS wouldn't let me open the file because of security issues.
I haven't downloaded Open Office to my new PC yet.
So MS offered to work for a limited few days as a special favour.
But wouldn't open it anyway.

[Cornelius Varley]

Here you go

[Tomatobro]

10 minutes ago, Cornelius Varley said:

Here you go

Thanks you beat me to it. Those numbers are milliamps

[Rusted]

Interesting. The AWR system drops in current during slews.

[Tomatobro]

To me it shows what happens when the Electronics, Software and Mechanical engineering folks don't talk to one another. There is no need to power the stepper motor to lock the position where worm and worm wheels are employed.

[Seelive]

Out of interest, what did you use to measure the current?

[Rusted]

21 minutes ago, Tomatobro said:

To me it shows what happens when the Electronics, Software and Mechanical engineering folks don't talk to one another. There is no need to power the stepper motor to lock the position where worm and worm wheels are employed.

Quite true. Then my understanding is even more limited than I merely imagined.
I thought I was quoting AWR. Who do indeed talk to each other.

[Rusted]

11 minutes ago, Seelive said:

Out of interest, what did you use to measure the current?

To whom was your message addressed? Tomatobro or myself?

[Tomatobro]

The folks at SW. Not having the current drop to near zero (which is what I expected) just made my life a bit harder. Now I have to map the current draw by the controller to determine when the scope is parked.

I used a Fluke 867B graphical multimeter. The display update averages the current draw but the min/max values were not that different.

Apologies if my comment was misinterpreted

[Seelive]

1 hour ago, Rusted said:

To whom was your message addressed? Tomatobro or myself?

It was intended for Tomatobro.

[Seelive]

53 minutes ago, Tomatobro said:

The folks at SW. Not having the current drop to near zero (which is what I expected) just made my life a bit harder. Now I have to map the current draw by the controller to determine when the scope is parked...

I assume that when the motor is not moving (parked), the stepper motor controller continues to output the (DC) phase currents that would be be normally be applied with the stepper motor at the 'parked' position as if it was still moving but at the 'parked' postion. So perhaps no AC current content (DC only) could indicate that the mount is parked?

[Tomatobro]

I did not want to get "inside" the mount but just monitor the power supply input. The latest version of Sharpcap has a sequence programmer with an end of sequence command to park the mount. I was looking to take an external action when the mount parked (close the observatory roof).

[malc-c]

No expert, but it's what I would have expected.   In an unpowered state it's quite easy to rotate a stepper motor (or servo motors for that matter), so in order to maintain a parked position both the RA/DEC (Alt/Az) motors have to be energised to hold the scope in that position, so all coils are being energised.  When slewing, there would be an initial surge in current to cover the torque needed to get the scope moving, and typically both motors are in motion for a period of the slew, .  But looking at the graph we're only talking around 100ma - 150ma difference between parked and tracking states... 

One thing it does show is the need for a decent 3amp or more supply, and why using a 2amp supply could cause issues.