GShield Power Consumption

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dereckd
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GShield Power Consumption

Post by dereckd » Thu Feb 13, 2014 10:04 pm

I'm trying to test out the electronics for my Shapeoko 2, I purchased a 24V 90W power supply which seam to work fine until I test the Y axis, with one motor its fine, with 2, it vibrates and does not move. I tried upping the current, on the POT but still no luck. Is 90W enough? there in no mechanical load, and I'm using the NEMA 17 motors, so I would have thought 90W would be ample.

ThinkItShapeIt
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Re: GShield Power Consumption

Post by ThinkItShapeIt » Thu Feb 13, 2014 10:57 pm

I would try lowering the current to the motors. The drivers maintain a constant current to the motors regardless of whether there is a load.

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dereckd
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Re: GShield Power Consumption

Post by dereckd » Thu Feb 13, 2014 11:34 pm

ThinkItShapeIt wrote:I would try lowering the current to the motors. The drivers maintain a constant current to the motors regardless of whether there is a load.

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Originally it worked with one stepper, which leads me to believe that it's not a problem of the current being to low ... (I do understand your load comment). I also have tried hooking up both motors, and sweeping through the pot little by little while testing ... at no point in the sweep do the motors work correctly ... they always seem to make noise. Maybe it's a gShield isssue or an issue with universalg-code-sender?

cvoinescu
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Re: GShield Power Consumption

Post by cvoinescu » Thu Feb 13, 2014 11:46 pm

Do you have the two Y motors wired to turn in opposite directions?

It may be that the impedance of the motors is so low that the driver can't cope with two of them in parallel. Try wiring them in series, it should be much easier on the driver.

To check that it's not the power supply being too small, power off, disconnect the X and Z motors (to reduce consumption), and try the Y with two motors again.
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

dereckd
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Re: GShield Power Consumption

Post by dereckd » Sat Feb 15, 2014 7:13 pm

cvoinescu wrote: Try wiring them in series, it should be much easier on the driver.
I'm following the instructions from the shapeoko 2 build , I'm not even certain how I would wire them in series ...
cvoinescu wrote: To check that it's not the power supply being too small, power off, disconnect the X and Z motors (to reduce consumption), and try the Y with two motors again.
Well, when I'm testing, I'm only testing one axis at a time .... correct me if I'm wrong, but there is no power consumption when the steppers are not running.

WillAdams
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Re: GShield Power Consumption

Post by WillAdams » Sat Feb 15, 2014 7:40 pm

The dual motor page on the wiki has wiring diagrams for both options: http://www.shapeoko.com/wiki/index.php/Dual_Motor

The motors draw current so as to hold the machine in position unless one disables that option.
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cvoinescu
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Re: GShield Power Consumption

Post by cvoinescu » Sat Feb 15, 2014 10:51 pm

What Will said, and note that gShield (and all motor driver shields for the Arduino Uno, including the buildlog.net shield and GAUPS) have a single pin that enables or disables all drivers. So regardless of how you configure GRBL, when you move one axis, all motors are powered up and engaged. Unfortunately, stepper motors draw about the same amount of power when moving and when stationary, so the fact that you don't move the other axes does not help with power consumption.
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

Nigel K Tolley
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Re: GShield Power Consumption

Post by Nigel K Tolley » Sun Feb 16, 2014 11:28 pm

Disconnect the motors only when the power is off!

(Just in case you don't already know)

As for putting them in series, that's quite easy. Undo the two sets of wires and wire them together. You need to have it so the power comes down one set of wires to the motor, then instead of returning to the board, it goes direct to the other motor, then back to the board.

Assuming you have two identical motors, it is fairly easy.

You have two sets of identical wires, A & A', B & B' for each motor. Simply wire M1 A' to M2 B, and M1 B' to M2 B. (Solder & wrap some insulating tape around them or use a block connector to keep them safe and in good contact - they aren't going in a socket now) The other wires that need changed are M2 A' & M2 B', which need moved to the same drive channel that M1 is using.

That should do it.

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cvoinescu
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Re: GShield Power Consumption

Post by cvoinescu » Mon Feb 17, 2014 1:04 am

Nigel K Tolley wrote:You have two sets of identical wires, A & A', B & B' for each motor. Simply wire M1 A' to M2 B, and M1 B' to M2 B. (Solder & wrap some insulating tape around them or use a block connector to keep them safe and in good contact - they aren't going in a socket now) The other wires that need changed are M2 A' & M2 B', which need moved to the same drive channel that M1 is using.
You have a typo and a "thinko". You probably meant Simply wire M1 A' to M2 A, which would put the motors in series. However, they would both turn in the same direction, which is not useful for a dual-Y setup. You need to swap some wires -- for example, swap the wires of one pair in one of the motors. Connect M1 A' to M2 A, and M1 B' to M2 B', and wire the remaining four wires into the driver (M1 A, M2 A', M1 B, M2 B). There are other ways of doing it (see the diagram on the wiki).
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

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