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bipolar stepper help

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Killa-X

Fri Jul 16 2010, 11:33PM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
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Posts: 1039

I always had plans to upgrade my scanner motor to a NEMA motor. I recently received 2 NEMA 23's in the mail for a CNC project. My scanner motor, was a 5-wire unipolar motor. So I was able to drive it easily with TURBO-CNC and a ULN2003. Clearly, this doesn't work for a 4-wire bipolar.

Is there any simple schematics I can use to test a bipolar stepper motor? A lot that I see out there are going to require chips I dont have. I'm looking for a way to do it with parallel ports, and I doubt its possible to make a ULN2003 work with it.

I just want to make sure these motors work is all before I go off making my more advanced driver.
Thanks!

Adam Munich

Fri Jul 16 2010, 11:40PM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

Here's something i drew up for someone a while ago. It uses the $11 a3967slb IC. It really doesn't get any easier than this. Parallel ports are not ideal for driving bipolar steppers, especially at high speeds.

Killa-X

Sat Jul 17 2010, 04:06AM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
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Posts: 1039

Hmmm...I know a driver that works good for doing 6-wire bipolar, with MACH 3 to get that 3000+rpm. Been asking the guy if it can be moded to with with a 4 wire then...It should, because a 6 wire just allows half-steps I believe, still 2 sets of coils but with a middle tap.

Adam Munich

Sat Jul 17 2010, 04:33AM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

Just leave out the center tap and it's a 4 wire.

Killa-X

Sat Jul 17 2010, 07:00AM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
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Posts: 1039

Grenadier wrote ...

Just leave out the center tap and it's a 4 wire.

True but the center tap is what gives you your forward/reverse :)

I had hopes to hook this up to the motor, since this driver can work with MACH 3. Maybe I'll try asking the people on youtube driving their NEMAs on Mach3 at 3000+rpm, just to bounce ideas!

To connect one of these...

The first one will require 8 connections, the second one 4 connections. Which may work with the driver I posted in the schematics...X = Forward, Y = Reverse. For one phase. Given 2 phase, 4 wires...X1 X2 Y1 Y2 should connect to the driver, I think...Please correct me if I'm wrong.

Dr. H.

Sat Jul 17 2010, 07:08AM

Registered Member #931 Joined: Mon Jul 30 2007, 05:25PM
Location: Bulgaria
Posts: 486

Hi Killa-X

All (well almost) stepper motor drivers work with STEP and DIR inputs. So don't worry - you won't have to change the software, and if you have a self decent PC you can reach amazing speeds (in 99% of the cases the speed is limited from the mechanics/motors/electronics).

Read a bit more for stepper motors - how they work and how to drive them as it seems you don't have a pretty clear understanding (no offences here).

There are quite a lot of DIY bipolar drivers outhere that are done with basic ICs (counters) and descrete output stages.

Cheers

Adam Munich

Sat Jul 17 2010, 07:17AM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

^Forward and reverse are controlled by the polarity+sequence of the coils.

Killa-X

Sat Jul 17 2010, 07:25AM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

Yeah. I had a unipolar stepper and it I know how that works, as its drivers are extremely easy. One wire gets 12V, the other wires are gate-triggered to ground. You can simulate a driver by tapping the pins, in order, to make it go step by step. Simply go 1 2 3 4, 1 2 3 4, 1 2 3 4.

Bipolars I understand mine has 2 coils. In order to go reverse, you have to reverse the current flow. From my understandings, to get a turn forward, you apply current to phase 1, and then phase 2, then phase 1, then phase 2. Keeping the flow direction the same.

So yes, My understandings of bipolar is hazzy, Since I'm use to unipolar.

Dr.H, I seen people rev NEMA 23's to 4000rpm with commercial drivers with MACH 3. I will hopefully be using MACH 3 on my old Dell Dimension 4600, XP. I forgot the speed but it's over 1.8ghz.

I guess also the use of flip-flops could make life easy too.
Polar

Or a L293D chip, which would require inputs like 1100 0110 0011 1001

Ok, The reason unipolar is easy to be is because I understand how to make it rotate MANUALLY by tapping the wires with the leads. I don't know for a bipolar, otherwise it would be far easer to picture how it works by manually tapping + - 12V.
Manualao

Is this wrong?

Lethal Shot

Sat Jul 17 2010, 08:42AM

Registered Member #1623 Joined: Tue Aug 05 2008, 03:31PM
Location: The Netherlands
Posts: 39

The picture is correct however applying +-12V to the coils without some sort of current control will ruin your steppers.
Just use the methode in the picture but as power use a battery.
I've tested my own motors this way and it works great and you can't cause any damage to your motor.

Killa-X

Sun Jul 18 2010, 07:16AM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

Slowly I think I'm getting it.
If the correct order, is as follows: The directions are just given concept.
+ - X X (forward)
X X + - (forward)
- + X X (backward)
X X - + (backward)

Then if we use this schematic: http://www.cs.uiowa.edu/~jones/step/circuitsf/14.gif
we will have X1 Y1 X2 Y2
X1 = forward - phase 1
Y1 = backward - phase 1
X2 = forward - phase 2
Y2 = backward - phase 2

It would be correct to say, the correct order, is X1 X2 Y1 Y2, and loop for motion. Y2 Y1 X2 X1 for the other direction.

Let me know if I got this right, If so, I see how it wont be too hard to wire this up to my driver :) Even a simple TURBOCNC ULN2003. Which I connect the wires correctly, so in turbo CNC its as simple as
1000XXXXX
0100XXXXX
0010XXXXX
0001XXXXX
Same as my unipolar.

There's no harm using a fullbridge directly connected to the motor right? You said you want a current limiter, but my motor takes 12V 0.7A per phase, 24V 1.4A stepper. My current testing PSU is 12V 300mA

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