2 Motors, 1 Controller

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fasteddy
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2 Motors, 1 Controller

Post by fasteddy » Fri Feb 13, 2015 6:57 pm

Given that the resistors allow the controller to reduce the current to motors rated at less than 3.5A, would it be reasonable to assume that 2 nema 17s rated @ 1.7A could run in parallel off a single controller without a resistor?

WillAdams
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Re: 2 Motors, 1 Controller

Post by WillAdams » Sat Mar 21, 2015 12:45 pm

Shapeoko 3XL #0006 w/Makita RT0701 Router w/0.125″ and ¼″ Elaire precision collets
Nomad 883 Pro #596 (bamboo)

cozmicray
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Re: 2 Motors, 1 Controller

Post by cozmicray » Sat Mar 21, 2015 10:07 pm

Huh?
resistors?
Where would you put these resistors?

Actually a circuit on the stepper motor driver sets the current
and another limits the current to the stepper motor(s).

I have been running 2 Nema 17s off of one polulu driver on a 3D printer
(RAMPs) with NO problem

Two Nema 17 motors on shapeoko 2 (Y axis) are driven off one G-Shield driver
with NO problem and NO resistors.

fasteddy wrote:Given that the resistors allow the controller to reduce the current to motors rated at less than 3.5A, would it be reasonable to assume that 2 nema 17s rated @ 1.7A could run in parallel off a single controller without a resistor?
:?:

cvoinescu
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Re: 2 Motors, 1 Controller

Post by cvoinescu » Tue Mar 24, 2015 3:55 am

cozmicray wrote:Huh?
resistors?
Where would you put these resistors?

Actually a circuit on the stepper motor driver sets the current
and another limits the current to the stepper motor(s).

I have been running 2 Nema 17s off of one polulu driver on a 3D printer
(RAMPs) with NO problem

Two Nema 17 motors on shapeoko 2 (Y axis) are driven off one G-Shield driver
with NO problem and NO resistors.
RTFM before assuming the OP is stupid.

Gecko G540 (we're in the Gecko section, this is not a gShield) uses a resistor inside the 9-pin motor connector to set the current. No resistor means 3.5 A.

There are two problems I see with running it with two motors in parallel and no resistor. First, if the wires to the motors are not the same length, the current will not distribute exactly equally, so one motor may get a little more than it's rated for. I'd set the current to 3 or 3.2 A, to be on the safe side. Also, not a good idea to run the Gecko without a current setting resistor even at 3.5 A, because it doesn't go into reduced current mode without the resistor.
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

fasteddy
Posts: 67
Joined: Sun Mar 24, 2013 10:27 pm

Re: 2 Motors, 1 Controller

Post by fasteddy » Thu Mar 26, 2015 4:21 pm

Indeed, there seemed to be some confusion about my initial post. I figured since I was posting in the Gecko section, not much more detail was necessary, but in retrospect maybe I should've been more explicit. That's good feedback, cvoinescu, and largely the conclusion that I came to myself. I had previously been using a 3-axis TB6600HQ controller, and I was really just trying to avoid rewiring to accommodate the 4th controller on the G540. However, whenever possible I try to stick with the adage that if something's worth doing, it's worth doing right, so I did in fact wire each motor independently.

And I must say, the G540 is so much smoother than my previous controller it's like night and day. It was much more expensive, true, but when you buy those cheap Chinese controllers you end up paying more in the end.

Anyway, early days with the G540, but I am extremely satisfied so far.

thebenj
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Re: 2 Motors, 1 Controller

Post by thebenj » Tue Apr 14, 2015 9:37 pm

im a tad lost on the resistors to buy for my similar set up. I'm considering using one axis for dual y, so i think i would need 3.2a with resistor and single motors on an axis 1.5a with my nema23 1.7a.

can anyone link me to the correct ones?

also when adding the resistors does polarity matter?

cvoinescu
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Re: 2 Motors, 1 Controller

Post by cvoinescu » Tue Apr 14, 2015 10:00 pm

The resistor is simply 1000 ohms for each amp of current you need -- so if you need 3.2 A, you want a 3.2 kΩ resistor (the manual recommends 0.25 W resistors). That's not a standard value, but you can get close: 3.16 kΩ or 3.3 kΩ are commonly available. 1.5 kΩ is standard, and 1.69 kΩ and 1.8 kΩ are close to 1.7 kΩ.

Here are some part numbers from Multicomp, a manufacturer of "generic" electronic components:

1.5 kΩ 0.25 W metal film resistor: MF25 1K5
1.8 kΩ 0.25 W metal film resistor: MF25 1K8
3.3 kΩ 0.25 W metal film resistor: MF25 3K3

1.47 kΩ 0.25 W metal film resistor: MCMF0W4DF1471A50
1.69 kΩ 0.25 W metal film resistor: MCMF0W4DF1691A50
3.16 kΩ 0.25 W metal film resistor: MCMF0W4DF3161A50

You can find these at Farnell, for instance; search directly for the part number.

Resistors are not polarized, you can connect them either way.

Edit: one word of warning. When running two motors on one driver with a beefy driver like a Gecko, make sure your connections are secure. If a wire to one of the motors disconnects, the other one will get the full current, and will probably be toast in much less time than it takes to make actual toast.
Proud owner of ShapeOko #709, eShapeOko #0, and of store.amberspyglass.co.uk

thebenj
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Joined: Mon Dec 09, 2013 7:49 pm

Re: 2 Motors, 1 Controller

Post by thebenj » Tue Apr 14, 2015 11:23 pm

thanks for the help once again catalin :D

danimal
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Re: 2 Motors, 1 Controller

Post by danimal » Mon May 25, 2015 9:15 pm

Just for future reference, these exist:

http://www.soigeneris.com/ez_g540___set ... tails.aspx

They make life a lot easier, and if you are going to spend ~$10 - 12 on resistors and DB9 connectors these are 100% easier. Plus they allowed me to tune the resistances for the dual y issue that you have listed above. I found that they ran best between 2.8 and 3 kOhm, and heated about the same as the single motor channels did.

Also don't forget to do your motor tuning.

https://www.youtube.com/watch?v=7EEXFu1beHI
Shapeoko # 1458

RT0701C Spindle || dual y motor || x axis nema23 with custom carriage 1000mm length || z axis nema23 linear rail upgrade with 1/2-10 ACME

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