Unipolar stepper motor with ULN2003?
 

hi

Last time I was designing like this http://www.eleccircuit.com/wp-conten...allel-port.jpg. I attack this to computer before start computer. After start I write codes and run only 3 steps. I find that IC and motor are going very much hot, then I disconnect all connections to IC. It really was near to be burnt, if I do not disconnect. What was the problem in circuit? I think it may be in its ground or +12V wire. Is it?

Are you using this to build your MechMate?

The ULN2003 is rated to have only 500mA current. The stepper motors most commonly used on this website draw many times that much current.

Because the ULN2003 is simply a darlington driver, it is not suited for anything but the most elementary interface. The Geckodrive stepper drivers are much more sophisticated in their design and in their ability. I doubt that the ULN2003 would be useful.

I have found the reason not the solution, it is that I am using the computer power supply. The +12V point has 6 Amp, as written on info sticker of computer power supply. But ULN2003 require only 0.5 Amp, that’s why my whole system was getting so much hot. But how to arrange the correct power supply (12V & 0.5 Amp). Which is cheep & easy source?

wal-mart plug. cell phone charger...

Bilal, the amount of current available from your power supply, 6A is NOT the reason the whole system is hot. The heat is because your motors want more than 0.5 Amps, and the drivers cannot furnish it.

Reducing the current available using a very small supply will cause that supply to tend to overload and heat up, and will provide very poor performance as well.

The ULN2003 is simply not close to driving the motors of a mechmate; The motors on the mechmate need to be provided something like 140 Watts worth of power or more to work well. If you try to do that at 500ma, you would need 280 volts or so, which I'm sure is well out of the specification range of the ULN2003.

Bilal,

Read Brad's post again and again.

A motor DRAWS as much current as it needs from the power supply. If the power supply or the stepper driver chips cannot handle the current that the motor needs, they will melt.

In a DC device, Current = Voltage / Resistance, so to reduce the current flowing through the ULN2003 device to 0.5A, when the power supply is 12VDC, the resistance would have to be increased to 24 ohms. (12 volts / 24 ohms = 0.5 A).

Increasing the resistance will destroy the performance of the motor. On a CNC machine, you will need many thousands of steps per second (25,000 to 45,000 steps per second). With a resistor added to the motor, you will get performance equal to the old floppy-disk controllers, which was about 1,000 steps per second maximum. That won't work. Also, reducing the current will destroy the amount of torque available. In other words, reducing the current could easily make it impossible for the motor to turn its own shaft.

You need to buy high performance stepper drivers and you need to use a power supply that supplies both the optimum voltage for the motor and sufficient current to let the motor do its work.

There is no one-chip solution for a high-performance stepper motor. You need to buy a driver package from a company that has built high-performance stepper drivers. I prefer Geckodrive. Others have used drivers from other companies. Read this forum and see what users near you are using, then you will know what is available and what works.

-Mike

The is the same conversation posted over at Mach3 Forum.

http://www.machsupport.com/forum/ind...&topic=15307.0

Medicine not taken.

I find some thing written on my motor. That is:
60C 45
5 DEG 13 (ohm) MAS
You can also read more about this motor from http://www.compucanjes.com/products/view/14268.html. what is basic formula to set at any system.

Using power transistors like TIP120 is also batter. But would you like to suggest me a good professional design of stepper deriver of medium level? You may suggest more than one.

The uln chip is not suitable for this or any cnc application. If you are really dead set on building your own drivers, http://www.pminmo.com/ is a good site with many proven designs, board layouts, parts list the whole deal. :)

Using TIP142 insteed of TIP120 to run stepper motor.
 

I am going to use TIP142 in steed of TIP120 in the following picture and want to operate the stepper at 24V. so which resistor I should use? Or what is the rule of thumb to use resistor.
http://www.edaboard.com/attachments/...ln2003_756-jpg

Bilal,
It is not clear how you will be using these components to drive the stepper motor. There was also no picture attached to your post.

There is the address of pic

http://www.edaboard.com/attachments/...ln2003_756-jpg

If you are looking to make drivers for MechMate then better look at some drivers with microstepping, current reduction etc.
Drivers that I made and serve me well are Mardus-Kreutz. There are two versions and becouse I could not find some parts for the first one I made one named "simpler alternative"
here is the link on cnc zone, you also have there a pcb you can print and make your own I used one from user NASR1.

http://www.cnczone.com/forums/showthread.php?t=38873

If you need further help feel free to contact me.

You can also try www.pminmo.com

TIP142 Stepper motor driver
 

I am going to build following circuit to run stepper motor using TIP142. So is there any need to change any thing in this circuit? The schematic of circuit is attached with this post.

Bilal,
Your schematic is only partially complete. There must be more circuitry to drive the output drivers effectively. I am assuming here that you will be using step and direction signals as most of us do, so there must be some drive logic to accommodate this. Please look at some of the DIY designs at www.pminmo.com as I have suggested before to see what I am speaking of. These designs are proven, built and used by many and you can surely pick a design that meets your needs. Also as drawn, as soon as you drive any one of those output devices into saturation, you will short your supply to ground.

For Example

Mardus-Kreutz Unipolar Driver

Allegro SLA7062 Stepper Driver

A3977 Stepper Driver

STmicro L297 and L298 Stepper Driver

Bilal, looking at the two schematics you have posted, I'm becoming concerned about the safety of the computer you are using, and your own safety should you start to work with higher powered circuits.

There are pretty much NO designs that interface directly from a parallel port to the power stage of a motor driver without isolation and/or protection circuitry.

IT IS VERY, VERY LIKELY YOU WILL DESTROY YOUR PARALLEL PORT AND POSSIBLY YOUR COMPUTER AND/OR START A FIRE.

Designing electronics is not as simple as working out the logical or digital flow; all electronic designs have to deal with the messy, imperfect analog reality of the components involved.

Please, please take a look at the proven designs Heath has pointed out above, and save yourself much time, trouble, and money.

With all of that said, designing stepper motor drivers is pretty off-topic for this forum, which is centered on building MechMates. We're happy to help you build a MechMate, and we'll be interested in any successful electronics you apply to a MechMate, but for general help in designing electronics, you should seek another forum.