Stepper Expert Needed

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ShedBoy

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That does help, thanx BC. I am going to play with the small step one.

Brock
 

crob09

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ShedBoy said:
I am building a tool post grinder, I want to have direction and speed control so I was thinking of using one of the stepper motors I have laying around. I want to run it independently from a computer and was wondering if these two boards would do the job? The stepper I am looking at using has six wires coming out of it and is covered by the amperage and voltage range of these two units. Are these two boards what I need to make it happen. Or could someone explain what all the abbreviations are? The boards come from China and will probably not have instructions?
Those will work but since you want this stand alone you will need a micro controller of some kind, the more common is Arduino.
You can just use the I/O's on the Arduino and attach the driver board your showing, the Arduino obtains logic voltage threw the USB so if your running things without the PC you will need to supply 5v logic to Arduino and additional power to the driver chips you noted.
Another way is to use DC motors, you do this by using a Relay, this can also be hooked upto your Arduino PLC and will require less pins than the Driver board, the only problem being holding torque, as you know stalling a DC brushed motor with current supplied will damage it, unlike a stepper.

Whats more is if you use Arduino, thanks to the Atmega IC you can store data to it and have it not only act as a PLC but as a mini computer.

Two things to watch for:
Supplying the proper wattage.
Providing the motor with the needed Amperage.

Do not over power the motor, if it's a 12v Nema motor, give it 12V no more. If you supply more than the requested 12V the motor and IC will get warm. Also the IC on the driver board needs to be able to handle the motors needs.

Hope this helps,

Rob

http://www.whatisacnc.com
 

kf2qd

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ShedBoy said:
I have 2 steppers here which look the same, have the same numbers for voltage, amps etc but when you spin them have a noticably different feel. One is smooth with tiny little step feel while the other is very notchy feeling. They are made by different manufacturers. Is one better than the other?
Brock
May have been a while since the one was powered up and the residual magnetism has left the fields. Power up one set of coils and see if it shows more cogging. It is also possible that the weaker motor has been overheated and the magnetic core has weakend because of that. Test them under power and see what torque each motor develops.
 

RonGinger

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Do not over power the motor, if it's a 12v Nema motor, give it 12V no more. If you supply more than the requested 12V the motor and IC will get warm. Also the IC on the driver board needs to be able to handle the motors needs.
This is not correct. Stepper are current devices, what is important is that they are given the rated current. Driving them over current will indeed destroy, or at least overheat the motor.

A typical stepper driver uses a high voltage- as much as 25 times the motors rated voltage. It senses the current flow through the coil, and shuts off the flow when it reaches the set value. If you looked at it with a scope you would see a series of pulses of voltage. The term 'chopper' used to be used for thee, although I dont hear it so much now.

The reason for the high voltage is to get the current up fast. A stepper is a coil- an inductor, and current increases through a coil at a rate controlled by the inductance of the coil. But if the voltage is higher the current will reach its RL value faster.
 

stevehuckss396

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RonGinger said:
This is not correct. Stepper are current devices, what is important is that they are given the rated current. Driving them over current will indeed destroy, or at least overheat the motor.

A typical stepper driver uses a high voltage- as much as 25 times the motors rated voltage. It senses the current flow through the coil, and shuts off the flow when it reaches the set value. If you looked at it with a scope you would see a series of pulses of voltage. The term 'chopper' used to be used for thee, although I dont hear it so much now.

The reason for the high voltage is to get the current up fast. A stepper is a coil- an inductor, and current increases through a coil at a rate controlled by the inductance of the coil. But if the voltage is higher the current will reach its RL value faster.

I was thinking the same thing. Here is what is on my mill right now.

Keling 570 Oz motors

3.0 Volt
5.0 Amps per phase
0.6 Ohms
2.5 MilliHenrys Inductance


Maximum voltage for the drive supply based on my motor is.

32 * vmH Inductance on the motor = Drive Supply Voltage

This voltage cannot exceed the rated voltage of the drive. The Gecko's are 80 volt. Cheap boards can be as low as 24. It is also a good Idea to place a large capacitor as close to the drive as possible to serve as a storage tank for surge current.

I could go on with the math but I wrote a program to size power supplys for motors. I'll post it here.

It will give you the AC voltage that you need so you get the correct DC voltage after the bridge rectifier. It also will give you the minimum capacitor size. Divide that number by the number of drives if you put a cap at each drive. The minimum wattage for the number of motors is also there.



View attachment StepperSupply.zip
 

Tin Falcon

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This voltage cannot exceed the rated voltage of the drive. The Gecko's are 80 volt. Cheap boards can be as low as 24. It is also a good Idea to place a large capacitor as close to the drive as possible to serve as a storage tank for surge current.
I agree IIRC the voltage rating on the gecko 540 is 50 volts. I am running 36 . I would consider 48 to be the max.
Higher voltage = higher speed with a stepper. but with small hobby machines with less than 12" axis travel how much speed do you need. all choices in design.

I have heard the cheap 24 v boards are marginally rated at best. 20 v is about the max you can push them.
BTW thanks for sharing the program.
Tin
 

stevehuckss396

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Tin Falcon said:
with small hobby machines with less than 12" axis travel how much speed do you need.

It is not so much about speed but time. Without loosing steps I went from the cheap stuff to the good stuff. Rapids changed from 50ipm to 350ipm. Cut depths changed from .015 to .050 in aluminum. My weak link changed from steppers to spindle power. I make most parts in 1/3rd the time because I can plow thru the metal without loosing steps. Same or higher feedrate cutting 3X the depth.

The rapid speed saves time but not as much as you think. The time is saved by cutting more per pass at the same or higher feed rate. Higher voltage means higher torque at higher speed.
 

Tin Falcon

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well the more we learn the more we find out we did not know thanks for the clarification. I know I feel much better running an X-2 at 36 volts rather than 12 or 15.
Tin
 

stevehuckss396

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Tin Falcon said:
I agree IIRC the voltage rating on the gecko 540 is 50 volts. I am running 36 . I would consider 48 to be the max.

The max voltage varies from motor to motor depending on the millihenries. NEVER exceed the voltage rating of the driver. Remember this is a maximum and going lower wont hurt anything. The top end torque will decrease as the voltage drops off. All this information is on the Gecko website. I would check the site of the driver manufacturer for information and warnings before designing the power supply.
 

crob09

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stevehuckss396 said:
The max voltage varies from motor to motor depending on the millihenries. NEVER exceed the voltage rating of the driver. Remember this is a maximum and going lower wont hurt anything. The top end torque will decrease as the voltage drops off. All this information is on the Gecko website. I would check the site of the driver manufacturer for information and warnings before designing the power supply.
I agree whole hearted. The IC may be rated for higher voltage than the motor is rated at and yes you can supply more voltage to the motor if the IC can handle it, however it is not a good idea, Ensteins theory of relativity states that energy cannot be distroyed or created only transformed, since that is the case, if you supply a higher voltage to the motor the IC and motor will get warm, the energy is being disipated threw heat transfer.
Lots of DIY people will use ATX power supplies, you know the ones from an old desktop, these supplies provide no more than 12V and even then the voltage read will be closer to 10V, but they have the wattage needed to run just about anything. They also have IC's that prevent any problems by shutting off the ATX if a bad connection is found.

If you want to keep things running cool and not have problems, stay within the specs provided by the manufacturer, you can find the information on the Datasheet provided with your motors or by searching for the information online.
 

crob09

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RonGinger said:
This is not correct. Stepper are current devices, what is important is that they are given the rated current. Driving them over current will indeed destroy, or at least overheat the motor.

A typical stepper driver uses a high voltage- as much as 25 times the motors rated voltage. It senses the current flow through the coil, and shuts off the flow when it reaches the set value. If you looked at it with a scope you would see a series of pulses of voltage. The term 'chopper' used to be used for thee, although I dont hear it so much now.

The reason for the high voltage is to get the current up fast. A stepper is a coil- an inductor, and current increases through a coil at a rate controlled by the inductance of the coil. But if the voltage is higher the current will reach its RL value faster.
So did everyone get that? I think we should follow this persons advice....
"A typical stepper driver uses a high voltage- as much as 25 times the motors rated voltage"

So that means the TB6560's I have that are rated for a "VOLTAGE RANGE" (I think the key word there is "RANGE") of 12V to 36V I should connect 25 times that because the TB6560 IC is on a PCB or PWB right?
Besides the Motor will use all that extra electricity (somehow) even thoe it's rated at 12V, and Enstein is wrong for saying that Engery cannot be created nor destroyed only transformed.
What is your Axiom here? "Ronginger" Do you have any video showing your work?
I want to see this concept put to use!

See I always figured a range ment that you can play within that zone, meaning if I have a range of 12-36V I can connect a motor and power source equal to 12V and up to 36V.
 

stevehuckss396

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Hey crob09!


Mr. Ginger's information is spot on. I think you need to spend a little bit of time over at the Gecko Drives website and do some reading. He is talking about the supplied voltage to the drive not the motor. The drive then delivers a constant current to the motor. I supplied 50ish volts to my drives with 3 volt motors. They are 5amp per pole and the 5 amps are controlled by the drives. The supply voltage is calculated using the motors inductance. It's voltage rating means nothing.

There is a wealth of information on that site along with all the math. Give it a look see.

http://www.geckodrive.com/faq.html


crob09 said:
What is your Axiom here? "Ronginger" Do you have any video showing your work?
I want to see this concept put to use!

Everyone who uses Gecko drives can show a video of this concept. This is how they are used. As far as voltage range is concerned, my DRIVE is rated 18 - 80 volt so 50 is within that range. Never exceed the volt rating of your drive!
 

steamer

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Right Steve you don't need to look far for Ron's great work

You can start with this fine organization
www.neme-s.org

Dave
 

Don1966

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I think everyone is beating the same drum here. The maximum voltage of the chip should never be exceeded and the controller has current limiting by installing a resistor and the motor will not draw more current than the selected resistor will allow, no mater what the voltage is. If the motor is rated 2.5 amp it will not draw more than allowed and the voltage drop across the motor will not be more than the rating of the motor because of the current limit.

My 2c
Don
 

Tin Falcon

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Don and that is the difference between a cheap controller board 24v give it 25 and it fries . a g 540 quality hobby machine controller 50 volts. Conservatively rated, and a gecko commercial controller 80 volts.
Tin
 

Tin Falcon

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A typical stepper driver uses a high voltage- as much as 25 times the motors rated voltage. It senses the current flow through the coil, and shuts off the flow when it reaches the set value. If you looked at it with a scope you would see a series of pulses of voltage. The term 'chopper' used to be used for thee, although I dont hear it so much now.

The reason for the high voltage is to get the current up fast. A stepper is a coil- an inductor, and current increases through a coil at a rate controlled by the inductance of the coil. But if the voltage is higher the current will reach its RL value faster.

Ron is correct if you use the gecko motor as an example
The G723-280-4 is a NEMA 23 4-wire 1.8 degree stepper motor specifically meant for the G250, G251 and G540. Built in the USA to extremely demanding quality control specifications the G723-280-4 is the perfect balance between linearity and holding torque. The motor includes two 3.48K 1% resistors to get the best performance when using the G540, G250, or G251.


Holding Torque: 280 oz-in
Number of Wires: 4
Dimensions: 3.1" (79mm) x 2.2" (56mm) x 2.2" (56mm)
Degrees Per Step: 1.8
Current Rating: 3.5A
Voltage Rating: 2.45V
Inductance Rating: 3.6mH
Resistance: 0.7 ohms
Rotor Inertia: 2.6 oz-in^2

the formula for max voltage is 32 * (square root of L) = voltage max where. L= impedance in milihenrys or 60 volts which is approximately 25 times the rated voltage. and since the max voltage of a G540 is 50 volts a 36 or 48 v power supply would be in the range.
Tin
 

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