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Different take on balancing


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16 minutes ago, Graham said:

I use a scientific power supply for the obs.

I get a continuous readout of what amps are being drawn.

Maybe something like this could be added to my power box, wiring into the connector that powers the mount 


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22 minutes ago, RonC said:

That looks good David, but how would I wire that into the system??

i could fit to my power box or grahams you could fit connector to so its inline to your wire that powers mount ,quite like grahams link 

Edited by Bottletopburly
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3 hours ago, RonC said:

Had to cancel the order! It needs to have a voltage current read out, most only have voltage readout.

Bit more researching I think!



All clamp meters will measure current, the problem is that the cheap ones normally only measure AC current rather than both DC and AC current. To measure the current drawn by the mount, it needs to be capable of measuring DC current.

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My mount is an Alt-Az Goto with a built-in battery, but I decided to give this a go anyway.

I have a digital ammeter which I plugged into to the 12V DC power line feeding the mount.  It always read some drain because the battery was being charged even when the mount was off.  I decided against disconnecting the battery internally to remove the charging current because it was too much faff. 

However, the meter did read an increased drain when the stepper motors were turning.  But there was no consistent pattern between left and right, up and down movements.   Not only did I not get the same current draw every time a motor moved in a given direction, but you didn't even get a consistent pattern (e.g. clockwise rotation draws less than anticlockwise).  OK, there's a lot of variables in play here, but I think good old gravity balancing is likely to be as good as an ammeter-based version.

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I think you could be right Bryan, there are a lot of variables at play to solely rely on the ammeter. It could cause just the damage you were hoping to stop. I agree also that the gravity method is tried and tested and it does take a bit of getting it perfectly right, but imagers seem to like a bit of loading to keep things stable.

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I can understand how the current in DC servo motors (as typically used in the smaller Alt-Az mounts) would vary with changes in the load torque but, based upon how I understand steppers motors work, I can't see how the current would vary with a changing torque load.  The motor current is set by the controller and that current provides a torque detemined by the motor characteristics. If that torque is exceeded then the stepper motor will just miss steps. But then I haven't tried it so I could be talking a load of ...

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Well I've ordered an in-line meter as above suggested by David but I used the hand held meter yesterday and got quite a shock (not electric!)

I had to move my weights 2" up the mount arm to get it to read out the same amperage!

I'll check tonight to see how it works and the difference it might make to my guiding!



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