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-   -   Question about stepper drives and motor direction (http://www.mechmate.com/forums/showthread.php?t=3106)

DTGuitars Sat 16 October 2010 11:24

Question about stepper drives and motor direction
 
Hey folks,

I found 4 drivers for my 34HS9801 steppers, 70V/6A. I do have a question before I purchase these. I noticed that there is only CW and no CCW connections. If running 2 steppers on the same axis as per MechMate design, would I need the CCW hook-up on my dirvers? Or, is this something that can be controlled through Mach3?

Best,
David

bradm Sat 16 October 2010 13:51

That question is a little difficult to parse. Almost all stepper drivers allow for both CW and CCW motion - it's a quite a bit limiting if the gantry only moves in one direction ;)

So normally, you would have two input signals to your driver, Step and Direction,, and for our motors, four output wires. If the motor does not run in the direction you think of as "Forward", then you swap one pair of the motor wires (reverse one winding of the motor). That will cause it to go the other way.

In the 2 steppers on the same axis case, you can either hardwire the motors as per above to run in different directions, or you can take advantage of the configuration in Mach3 or EMC2 to reverse the direction signal on one of the motors.

DTGuitars Sat 16 October 2010 14:48

Thanks Brad. That cleared up a good amount of stuff.

David

domino11 Sat 16 October 2010 20:51

Could it be that the CW line is CW when it is a high or 1 state and then the opposite or CCW when it is in a low state? Sometimes in electronics the input name reflects the logic 1 state. The manual might mention this. Basically the same as the DIR input on the PMDX?

Richards Sun 17 October 2010 07:32

Some stepper drivers expect to see CW pulses when the motor is to turn in one direction and CCW pulses when the motor is to turn in the other direction. Most of us do not use that kind of stepper driver. We use the kind that has an input for step pulses and an input for a direction signal. When we want the motor to turn one direction we send a 0V or 5V signal to the direction input (depending on the direction desired). No matter which direction we want the motor to turn, we send the step pulses to the step input.

All of the Oriental Motor stepper drivers that I have have a switch selectable option to use either CW/CCW or Step/Direction.

DTGuitars Sun 17 October 2010 16:51

Quote:
Originally Posted by Richards View Post
Some stepper drivers expect to see CW pulses when the motor is to turn in one direction and CCW pulses when the motor is to turn in the other direction. Most of us do not use that kind of stepper driver. We use the kind that has an input for step pulses and an input for a direction signal. When we want the motor to turn one direction we send a 0V or 5V signal to the direction input (depending on the direction desired). No matter which direction we want the motor to turn, we send the step pulses to the step input.

All of the Oriental Motor stepper drivers that I have have a switch selectable option to use either CW/CCW or Step/Direction.
OK. So............how would a person hook things up if their drivers did not have the selectable switch? Here are the connections as follows:

CP+
CP-
CW+
CW-
EN+
EN-

Then there is the obvious connection pins for supply voltage and motor windings. I suppose what I am trying to figure out is if the PMDX-122 board will work with these drivers, or if a different type board is required, and what board would it be?

Please forgive my ignorance on this stuff:confused:. It is all fairly new to me. The building of the bed and gantry, the mechanical stuff is no problem. When it gets to breakout boards and controllers/drivers, that is where I get a little lost in the details.

David

bradm Sun 17 October 2010 18:16

David, if you can point us towards the manual for those drivers, we might get you an answer more quickly.

DTGuitars Sun 17 October 2010 20:42

Hey Brad,

This is the best I can find as for information at this point.

http://oemotor.com/html/product_e_27.html

I hope this is enough info to help answer my questions.

David

danilom Mon 18 October 2010 02:47

There should be a jumper/switch inside, under the case to select the mode
CW-CCW / STP-DIR. Try to look

And it looks like the inputs are standard STEP/DIR

5、CP +、CP -:Stepping pulse input+5V (Rising edge effective , rising edge duration >10μS) --> (STEP)

6、CW +、CW-:Stepping motor direction input, voltage level touched off,high towards, low reverse --> (DIR)

if you dont get movement try to not connect anything od ENABLE inputs

Richards Mon 18 October 2010 03:36

The step, direction, and enable are opto-isolated inputs, with the (-) connection connected to Ground and the (+) input connected to a 5VDC signal line.

Connect CP(+) to the Step signal. Connect CP (-) to signal ground.

Connect CW(+) to the direction signal. Connect CW(-) to signal ground.

NOTE that the pulse duration needs to be greater than 10uSecs. (I'm writing this from a Linux machine, so I can't open Mach3 to see if it supports a 10uSec pulse.)

Set switches 5 & 6 = OFF and switches 7 & 8 = ON for 1/10th microstepping (which is the same microstepping as the Geckodrives that many of us use).

Set switches 1, 2, and 3 to match the current rating of your motors.

Set switch 4 = OFF for automatic current reduction when resting. (Many stepper drivers have automatic current reduction set by default. The stepper driver will get very hot if automatic current reduction is not used.)

Mount the stepper driver onto a heat sink if the motor pulls more than 3A.

DTGuitars Mon 18 October 2010 07:20

Hey, thanks guys. That was most helpful for my understanding. I have not completely made my mind up on what driver to go with. These were offered to me at a really low price. I made a discovery last night that is possibly leading me away from these drivers. It looks like (and this could be a typo) that the maximum pulse rate is 200HZ. Does this seem extremely low to anyone? Do they even make stepper drivers this low in pulse rate? I believe that Mach 3 only goes down to 250KHZ.

David

bradm Mon 18 October 2010 08:18

I can't vouch for those drivers, but 200Hz pretty much has to be a typo.

A standard, 1.8degree per step motor needs 200 pulses in full stepping mode to make a revolution. So the maximum speed of this driver would be one revolution per second.

If you used it's highest microstepping setting, it would take over four minutes per
revolution.

If I make the assumption that it's supposed to be 200kHz, everything makes more sense; max speed of 1,000 RPM (or less with microstepping).

As for Mach 3, I think we're talking apples and oranges. That frequency refers to how fast the system *can* update the motors, not how fast it *must* update any particular motor. It can and does output much slower pulse rates when you want a motor to move slowly. Although the software is processing 250K (or more) updates per second, many of those involve doing nothing, because it isn't yet time for the next motor pulse to go out.

DTGuitars Mon 18 October 2010 08:48

Brad,

So these could possibly do the trick, and would work with the PMDX-122 breakout if the wiring follows suit to what Mike states above? I mean, at $25 a piece, it would be good at least to use until I can get my reduction boxes cut out for my motors, and for use until I can get some more $$$ for higher quality Gecko drivers.

David

bradm Mon 18 October 2010 09:38

David, if they meet the published specifications (check with them about the 200Hz vs 200KHz before you buy), they should work.

There are several areas that have distinguished good stepper drivers from bad over the years:

- Amount of torque available at various speeds. Good drivers deliver a smooth torque curve over the speeds, with no discontinuities (weak speeds).
- Minimization of motor heating, while still maintaining good holding torque.
- Controlling the high pitched whine (from the motors) due to PWM switching.
- Amount of heat generated at the driver.
- Electrical noise generated, and sensitivity to external electric noise.

These drivers may or may not represent a compromise in one or more of these areas, and it's impossible to tell until you have them on a test bench or machine. I'll be interested to hear what your experience is. We have lots of good reports on the Gecko drives, and recently on the UIRobot drives. You'll have to let us know about these ones.


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