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Re: will1384's Shapeoko 2

Posted: Tue Aug 26, 2014 10:49 am
by cvoinescu
Using your multimeter (on volts DC, and if it's not auto-ranging, select the 2 V scale), measure between one of the solder joints circled in red in the image and ground (the screw marked GND on the two-terminal screw connector). Read the voltage, then follow the calculations to find out what the current is. Adjust by turning the small screw-like knob on top of the trimpot. Clockwise is more, counter-clockwise is less. Do not exceed the current rating of your motors, and take care not to touch anything else with the probes while measuring.

Re: will1384's Shapeoko 2

Posted: Tue Aug 26, 2014 5:29 pm
by sectorix
cvoinescu wrote:Using your multimeter (on volts DC, and if it's not auto-ranging, select the 2 V scale), measure between one of the solder joints circled in red in the image and ground (the screw marked GND on the two-terminal screw connector). Read the voltage, then follow the calculations to find out what the current is. Adjust by turning the small screw-like knob on top of the trimpot. Clockwise is more, counter-clockwise is less. Do not exceed the current rating of your motors, and take care not to touch anything else with the probes while measuring.
From which 2 points should I measure ? on the bolted bracket on grblshield? a picture would be wonderful

Re: will1384's Shapeoko 2

Posted: Tue Aug 26, 2014 8:49 pm
by secretspy711
cvoinescu already said it:
measure between one of the solder joints circled in red in the image and ground (the screw marked GND on the two-terminal screw connector).
Image

Re: will1384's Shapeoko 2

Posted: Tue Aug 26, 2014 9:48 pm
by cvoinescu
Yeah, what he said that I said. You had the picture in your own post.

Re: will1384's Shapeoko 2

Posted: Wed Aug 27, 2014 1:23 am
by sectorix
Thanks. will try!
obviously new at this

Re: will1384's Shapeoko 2

Posted: Thu Apr 30, 2015 4:20 pm
by tornwing
will1384 wrote:Part (4) wiring.

~

so I think I would need 1.3v on VREF

1.3 / 0.8 = 1.625


Is this correct?

I am going to finish wiring up the stepper motors and testing the CNC control box tonight, lets hope I don't let the smoke out of it :shock: LOL
Hi there

I am a newbie for shapeoko 2 assembly (also electrics).

I just bought gshield board for driving shapeoko 2 before a few months.

As you know, Y axis in SO CNC is driven by two stepper motors .

I looked up this post, if I wanna make stepper motor work efficiently, I have to adjust Verf on Gshield for rated current of stepper motor.

I got the caculation for I=Verf/0.8.

The rated current of my Nama 17s is 1.3A, so I adjusted Verf become 1.035 V (Iref=1.29).

However, in parallel, the currency will become larger. I remember gshield just serve 2.5 A. Once the Nama 17s are paralleled, the total currency (Iref in Y) will become 2.58A to damage Ti8818. Do I get wrong?

Thanks for your help.

Re: will1384's Shapeoko 2

Posted: Thu Apr 30, 2015 5:07 pm
by cvoinescu
Well, sort of. You're right that the rated current of the two motors in parallel will be 2.6 A, but that just means the DRV8818 won't be able to supply the full current. It won't break.

It's unlikely that you'll get close to 2.5 A without some serious cooling. I would simply adjust the reference to the highest current that doesn't cause the driver to go into thermal shutdown in your setup, then dial it back 20% or so.

Re: will1384's Shapeoko 2

Posted: Mon May 04, 2015 10:09 am
by tornwing
cvoinescu wrote:Well, sort of. You're right that the rated current of the two motors in parallel will be 2.6 A, but that just means the DRV8818 won't be able to supply the full current. It won't break.

It's unlikely that you'll get close to 2.5 A without some serious cooling. I would simply adjust the reference to the highest current that doesn't cause the driver to go into thermal shutdown in your setup, then dial it back 20% or so.
Hi cvoinescu

Thanks for your advice. :D

Because my stepper motor in the X-axis is Nema 23 driving in 2.5A, absoultely, I got the Verf close to 2.0V.

I know Ti8818 cooling is a big issue, so an 8cm fan and fins were prepared.

Thus, I also adjusted the Verf in Y axis almost 2.0.

I am not sure the cooling system is enough or not.

Image

Thank you so much.