Sesto Senso 2 Focuser Question about "Hold Current"

[Hogarth]

So I suspect my focuser may be slipping, due to the Sesto Senso 2 not holding it (not proven, but want to rule it out)

I have two rigs both with seperate Sesto Senso 2's fitted

The odd thing is, I've read from the factory the default preset is to to Heavy and Slow, but when I look at both mine.. This is indeed true, but the hold current is set to 1 on one focuser and 3 on the other focuser. ( I havent changed this and they were bought from new)

So I thought i'll just toggle through the three presets and see what the Hold Current changes to. Unfortunatly it sets it to 1 for each preset..

The manual literally says 
Hold: set the hold current, when the motor is stopped

Now if this is amp's, when i change the Hold value to 5 (the max it can be), I see no amp draw difference (I have a Pegasus powerbox, so useful to see the draw being made)

So the question is what is this Hold value and which is the right value to hold a heavy train. 

Thanks in advance

[teoria_del_big_bang]

I always assumed this was the actual current to hold the motor in place when not in motion but it will not be in amps for sure.
I doubt the focusser motor will even take an amp when moving full speed with a heavy load and the hold current will be less.

So I suspect it is just some arbitrary scale with 5 being the maximum current and 1 the lowest but what what that current is I have no idea. Also I suspect the current will be chopped (it will go on and off very fast frequency) to give a better hold but not burn out the motor coils so probably between 1 and 5 the difference in actual current could be quite small, but still I am suprise you can not see any small change in the current on the powerbox.

All this is my assumption as I too cannot find anything on Google to define what the Hold Current actually is.

Steve

[Carbon Brush]

Suggestion.

Write down the values before you start adjusting. You can always go back to these.

Position the focusser vertically. In other words lifting a load against gravity, not hoisting up a gradual incline.
Add something heavy - like a weight on a string. Heavier than a big eyepiece/camera.
Also if you drop the load......

Gradually reduce the run current until the weight is not reliably lifted.
Gradually reduce the hold current until you can just start to pull the weight down with a little force.

I'm thinking you will find the motor runs OK with fairly low values set. Now increase these by say 50% and run the scope.

HTH, David.

[Hogarth]

1 hour ago, Carbon Brush said:

Suggestion.

Write down the values before you start adjusting. You can always go back to these.

Position the focusser vertically. In other words lifting a load against gravity, not hoisting up a gradual incline.
Add something heavy - like a weight on a string. Heavier than a big eyepiece/camera.
Also if you drop the load......

Gradually reduce the run current until the weight is not reliably lifted.
Gradually reduce the hold current until you can just start to pull the weight down with a little force.

I'm thinking you will find the motor runs OK with fairly low values set. Now increase these by say 50% and run the scope.

HTH, David.

thanks, thats a great suggestion

[Hogarth]

3 hours ago, teoria_del_big_bang said:

I always assumed this was the actual current to hold the motor in place when not in motion but it will not be in amps for sure.
I doubt the focusser motor will even take an amp when moving full speed with a heavy load and the hold current will be less.

So I suspect it is just some arbitrary scale with 5 being the maximum current and 1 the lowest but what what that current is I have no idea. Also I suspect the current will be chopped (it will go on and off very fast frequency) to give a better hold but not burn out the motor coils so probably between 1 and 5 the difference in actual current could be quite small, but still I am suprise you can not see any small change in the current on the powerbox.

All this is my assumption as I too cannot find anything on Google to define what the Hold Current actually is.

Steve

thanks.. looking at other generic stepper motors, the hold current appears to be in shown in milliamps.. so maybe its 1ma to 5ma.

i'll keep looking, hopefully no "communication breakdown before the levee breaks"
 

[teoria_del_big_bang]

1 hour ago, Hogarth said:

i'll keep looking, hopefully no "communication breakdown before the levee breaks"

I hope that soon you are no longer Dazed and Confused and I suggest you give it No Quarter 🙂 

Good luck

Steve

[Franklin]

24 minutes ago, teoria_del_big_bang said:

i'll keep looking, hopefully no "communication breakdown before the levee breaks"

I'm sure that soon you will be "In the Light".😀

[Carbon Brush]

Just thought....

If you have a dial gauge indicator, you can verfiy the focusser returns accurately after and out and back, as well as establish if you can pull it off setting.

HTH, David.

[Clarkey]

On 07/12/2021 at 15:08, Hogarth said:

So I suspect my focuser may be slipping, due to the Sesto Senso 2 not holding it

Just out of interest, why do you think it the focus motor slipping and not the focuser itself? I have two if these focusers and there are both rock solid. The only slippage I have seen is the focuser slipping. What focuser are you using?