Universal Stepper Driver

What have you got so far, Uncle?

well as of now i just have a bunch of stepper motors but i have access to any component i will need . i don't know how to go about designing a circuit that can support both a unipolar motor and bi polar motor as such making a universal driver .

How come you've bought a load of stepper motors and you've no idea how to drive them?

Where did you get your steppers? They should have good application manuals.

( unless these are scavenged motors you got for nothing )

Slo-syn and others had excellent tutorials.

Copy the name from your stepper nameplate and type it into google or other search bar. You will be surprised how much help is available.

In fact there are dozens of " Universal stepper driver / controller" solutions you can buy already designed and proven.

You must first identify how many phases are these stepping motors. The common number of phases are 2, 3, and 5 phase stepping motors. Usually a uni-polar motor can be driven by a bipolar motor but a unipolar driver may not be able to drive a bipolar motor. So you should focus on bipolar driver topology. I recommend an H block topology.

There are already many embedded technology micro-computer companies that make programmable stepper motor chips. Allegro and ST are ones that I like but there are many on the market. To increase the current drive to 20A, these chips can just be connected to power MOSFET devices. (It may be tempting to just use the body diode of a MOSFET for the flyback current diode but I recommend using a Schotkey diode, too.) The two companies above have many nice application notes on how to use their parts. MOSFET manufacturers like International Rectifier also have excellent application notes on how to use their products.

Oh, I think that you will quickly find that a 12V supply may be undersized for any kind of speed. 48V and higher is much more common.

This can be a great project for learning how to use and expand embedded systems. At the same time this is a very well established field.

Good Luck

Lots of good comments from you, but did he understand?

To sum up - Unipolar drivers are for the the same motor, less powerful than the same motor driven as Bipolar as only half of the windings are activated at the same time in Unipolar mode....there are many web sites explaining all of this in great detail, have a Google!

So Bipolar driving allows more power, but true Unipolar drivers cannot be used on TRUE Bipolar only motors.

Unipolar drivers are generally cheaper than similar Bipolar drivers in my experience (for approximately the same power).

All normal Stepper motors can be driven Bipolar.....but not all can be drive Unipolar, so the OP needs to check each motor for type before buying/building any electronics....

(There are some mixed Hybrid motors that are not covered by my comments here!)

I agree with your voltage comments completely, 48 volts being a generally better driver than 12 volts....in fact in my (limited) experience, 12 volts is only used with very tiny motors....certainly nothing using 20 amps!! Maybe even less than 1 amp!!

To the OP, I would be surprised if any of the the motors you have collected took more than a couple of amps at even 48 volts, but surprise me.....

Driving motors is mainly a function of the internal impedance of the motor and as high a voltage as possible to get the maximum torque out of the motor. Low voltage and high current could easily exceed the heating/cooling parameters of the motor and damage it.

Assuming for a moment that I am right, and that few of the motors when driven correctly can handle more than 3 amps at any "normal" voltage without overheating, then look at the Allegro Motor driver chips.

They will save you months of designing, they do not need an external sense resistor (in the later versions at least, which is a great help) and have all the bells & whistles anyone could ever need. Usually available for between $20-$40 per chip, depending upon the suppliers......It is a cheap way to go in the long run.

They also support micro stepping for really fine control if and when needed.

Look here:-

http://www.allegromicro.com/en/Products/Motor-Driver-And-Interface-ICs.aspx

Cooling is the single greatest problem that a beginner must handle....both with drivers and motors.....You will burn at least one motor when experimenting.....probably!!!

Best of luck, keep us informed....

Try an L298 hbridge driver followed by mosfets. I have found stepper performance to be lacking due to resonances. When you need power, you're better off with servos. When you need speed, you're better off with servos. I set up a 10 hp lathe motor with a Galil motor controller and a Baldor VFD and I could overdrive the 3000rpm motor to 8000rpm. Resonance in steppers limits speed and acceleration rate...over drive them and they stall.

"Jones on Steppers" is a very good resource http://homepage.cs.uiowa.edu/~jones/step/.

Does this help?

http://www.st.com/st-web-ui/static/active/en/resource/technical/document/application_note/CD00003774.pdf

thats how it works, hope you can read the circuit

http://home.cogeco.ca/~rpaisley4/Stepper2012Bipolar.html

I have come across a link that has a driver which can be used for both unipolar and bipolar steppers . My aim now is to replace a few components so that i get a continuous output current rating of 20A at . I want to also use MOSFET's instead of Darlington type transistors . Could anyone guide me as how i could go about this ?

Here is my email reply that you requested:-

I have only one question, why?

But maybe I can still make some useful suggestions without knowing, but better ones once I understand the reasons for your question.

But by NOT including the rest of the Guys on CR4, means that possibly good ideas will be lost or forgotten. You need to address everyone here for best results, though there is always some "chaff" that needs to be "winnowed" out, as in any broad discussion on the internet.

Here is a possible better start for you, already designed, but Unipolar:-

20 amp stepper motor driver

The only stepper motor that I know personally know of (there will be some others, but quite expensive, outside of a hobby!!), that can use around 20 amps at 12 volts is a re-purposed, re-built (needs a big thick magnet or electromagnet, using a DC power source for example) car alternator.

See here on YouTube, someone has done a lot of the work for you!!:-

Part one

Part Two

Part three

Part four

I have also placed my complete answer to you, (not your question, that you should do yourself if you wish!) on the blog, as most of the brains there are good and worth including.

If you need some help as to who to believe and who not to believe (though I personally find it quite obvious after a couple of posts from anyone), then let us talk using CR4 email, offline so to say.

I would like to add that we have quite an active "Offline" membership on CR4 email and private email, as not everyone has studied the subjects on which they are posting! Sadly!!! But we know who is useful and who is just trying to make himself appear useful!!

My REAL email address (which is NOT to be put in any blog - CR4 Rules -, or emails to ANY others here, by the way by you Only I may, if I wish include it, as there are some ignorant Choleric members as well sadly!!! (to put it mildly!!)

You will get to know them and errors of their ways. You may, as you wish either point these failings out or simply ignore them!!

Although this is a Blog for Engineers, all are welcome, all may post, but not all know what they are talking about!!!

I for example, have never made ANY stepper motor of any size or shape, I simply buy them cheaply on ebay when needed.....None of them (up to now anyway!) required more than 3 amps at 48 volts either!!! Most only 2 amps.....or less!

Regards

Andy G.

I completely agree, why?

I have no need or desire to design a simple single channel whole step stepping motor driver. I applaud anyone wanting to design any circuit design and am willing to help one who stumbles along the way that show initiative. Instead of taking one of the variety of chip designers suggested to you, you wish for somebody here to boost the current of a primitive stepping motor driver. You didn't listen to my earlier advice...

Why?

Thanks for your support redfred in this matter.

Also, that's really good quality support as I know from long experience together, even if we do not always see "eye to eye" with each other 100% of the time! I know that I can live with that!!

I still hope that you found my previous comments to arjunv8 about CR4 acceptable/accurate! Let me know either here or on email.

I also have to agree with your other comments as well in your post, as I also prefer to use my time, knowledge and ingenuity on the parts of projects that are enormously expensive or simply not available otherwise.....

I feel that probably arjunv8 is simply not quite in the position of being knowledgeable enough to fully understand what he REALLY needs at this time, hopefully that will come!! We need to help him.

He appears to be a very reasonable person and a future plus for CR4 in all other respects....I hope you and the rest of CR4 all agree fully.....

What did you think of that huge Stepper Motor I found on YouTube? You could open a heavy door with such a unit, quite exactly too!!

You all have a great day.

I like it. Now if I could only find one on Craigslist (for a price I could afford)!

Hey , guys . Thanks for all your valuable inputs . The reason as to why i'm continuously asking you guys for help as to how i can alter this circuit is because it's a project which is a part of my coursework that i must complete. I'm an engineering student and my knowledge is still very limited . As for why i cannot use an alternate design is because this is the exact circuit i have to use as per the guidelines given to me by my professor . I appreciate all the inputs you all have given me but i'm still learning about all these concepts involved .

Now my main aim is to try and replace all darlington transistors with n channel mosfets .

Does anybody have any ideas as to how i can go about this ?

Theoretically, it should not be too difficult to do once you have mastered the technical details of BOTH devices and you have access to data sheets.

Again though you don't say why you need to change the transistors and CR4 works better when they understand why....please explain!

Hey andy ! As to why i have to replace the transistors it's because n channel mosfets have faster switching times as compared to the transistors used . Also for such a high amplification of the current from 1 A to 20A it's best suited for power mosfets . Mosfets are voltage controlled devices where as transistors are current controlled . My aim is with a 12V supply to get a 20A current , thereby that's why i want to use a mosfet .

I hope this gives you a better understanding . My problem is when i modify the circuit from using transistors to mosfets the logic changes . If you look at the circuit you will be able to see that . i dont know what is the logic that will be required for mosfets and i'm currently brain strorming for ideas . i hope you can provide me with some ideas . !

Drive the mosfet with an open collector xistor tied to the rail with a current limiting resistor.

Why the current limiting resistor? Oh, I guess you mean a pull up resistor. That can be made to work once the frequencies are known.

Now that is something usually cheap and easy to make (assuming you meant the Car Alternator Stepper motor!). Finding an old alternator with a lower output (as alternator of course!), will allow lower maximum currents, though proper control of the driver design can do the same.

My thoughts are for this blog for anyone interested:-

Looking for one in a junkyard is probably the best place.

You would probably need to use a DC supply to the rotor as I personally haven't a clue where you would find a magnet to use in the rotor, though the people on YouTube who do this and the ones that make windmill generators seem to be able to find them somewhere...

I did find these on the German ebay, thats about $2,50 each, 5 or 6 placed one on the other would make a great replacement for the wound rotor. Individually they lift up to 11 Kg., more than 22 Pounds....

Actually, soft iron spacers to make it "fit" the alternator would be enough, and also cheap and easy to make......same effect in the end with such a magnetic "sandwich" with such a magnet clamped in the middle.....even steel parts might work enough, I haven't done such things for many years, so experiment!!!

See here:-

Rundmagnet-Magnet-Scheibe-51-x-6-3-mm-11-kg

Or one of these drilled and turned down to fit maybe?:-

Neodym-Power-Magnet-80x10-mm-300-kg

Just some thoughts for general usage for CR4 members.

Hey andy ! As to why i have to replace the transistors it's because n channel mosfets have faster switching times as compared to the transistors used . Also for such a high amplification of the current from 1 A to 20A it's best suited for power mosfets . Mosfets are voltage controlled devices where as transistors are current controlled . My aim is with a 12V supply to get a 20A current , thereby that's why i want to use a mosfet .

I hope this gives you a better understanding . My problem is when i modify the circuit from using transistors to mosfets the logic changes . If you look at the circuit you will be able to see that . i dont know what is the logic that will be required for mosfets and i'm currently brain strorming for ideas . i hope you can provide me with some ideas . !

Firstly work out your maximum switching frequency needed, I doubt that it will be very high. Remember, in computer terms, steppers are SLOOOOW!! Really slow!

Always start with the basics first.....

Whats your highest switching frequency?

Hey andy ! As to why i have to replace the transistors it's because n channel mosfets have faster switching times as compared to the transistors used . Also for such a high amplification of the current from 1 A to 20A it's best suited for power mosfets . Mosfets are voltage controlled devices where as transistors are current controlled . My aim is with a 12V supply to get a 20A current , thereby that's why i want to use a mosfet .

I hope this gives you a better understanding . My problem is when i modify the circuit from using transistors to mosfets the logic changes . If you look at the circuit you will be able to see that . i dont know what is the logic that will be required for mosfets and i'm currently brain strorming for ideas . i hope you can provide me with some ideas . !

Magnets for this purpose are easily obtainable from the nearest microwave magnetron...already have a hole, might not be exactly the right size, but epoxy makes a nice shim.

Thats a great idea....anyone got some Photos?

No way to x-fer photos, but I measured one ( they vary in dia. per mfr of mag.) at 2-3/16" dia, 1/2" thick, 13/16 hole. There are 2 in each discarded microwave oven, and they are quite useful.

Many thanks, no foto now needed.

I started a reply when you initially posted but the universe got in the way again and I now see that I did not post that reply. I'm sorry.

Yes, I found your comments to arjunv8 to be acceptable and accurate. I also agree with your assessment that they could be an excellent addition to our wacky community. I too hope that they come back to us. I suspected the request for design help for a current boost to 20A was a homework assignment. What they may not realize yet is that their current boost circuit may be used with the micro-stepping circuit configurations suggested earlier. Learning how to design and fabricate a current boost will be an excellent learning experience. Particularly as they find the transistors working well until they start roasting themselves. This should drive them to include their thermodynamics training from a Physics class to adding a suitable heat sink. Then there's the added fun they'll quickly encounter with the fly-back voltage produced by trying to stop current flowing through an inductive load.

Once they show me some some effort and poignant inquiries I will gladly help them with their (not my) design.

As for the alternator transformed into a stepper, that was interesting.

Thanks. I liked that HUGE stepper too.....(Not that I have built one, but if ever I need such a device......)

Hey andy ! As to why i have to replace the transistors it's because n channel mosfets have faster switching times as compared to the transistors used . Also for such a high amplification of the current from 1 A to 20A it's best suited for power mosfets . Mosfets are voltage controlled devices where as transistors are current controlled . My aim is with a 12V supply to get a 20A current , thereby that's why i want to use a mosfet .

I hope this gives you a better understanding . My problem is when i modify the circuit from using transistors to mosfets the logic changes . If you look at the circuit you will be able to see that . i dont know what is the logic that will be required for mosfets and i'm currently brain strorming for ideas . i hope you can provide me with some ideas . !

hey guys ! now i'm replacing all the transistors with mosfets . Q1,Q3 are replaced with SiS443DN (40V,35A) and all the other npn transistors are being replaced by n channel (NVTFS5811NL) mosfets(40V,40A) . Now i need some help so that i can place suitable resistors between the various mosfets and loads . Does anybody have any suggestion as to what values i can use to keep a steady current of 20 A ? .

You've replaced the Bipolar junction transistors from #11 with a power MOSFET? That's not going to help. Which circuit diagram are you referencing?

As for current limitation, you must also know the complex impedance of your motor to limit the current with a fixed resistor. To make a universal driver you must measure the current sent and use feedback.

Dear redfred.

GA

How true!!

I can personally ONLY recommend a purpose built chip to do all the clever stuff, maybe beefing up the output drive with big "Trannies"....though I have never done anything like that myself....theoretically possible I would guess......but quite complicated in that the chip must somehow still get the sense/feedback as well.....not a fun job......to me that is reason enough to stay at 3 amps or less!!!

To the OP, did you actually tell us why you are fixed on 20 amps? If not please tell us ASAP!!!

Do remember that steppers actually are "stepped" (what a surprise!!), so only take current for milliseconds when moving and not when stopped = 0 Amps!!! (th usual "breeds" of stepper that is!)

They have for the beginner very little to do with "normal" electric motors, have you understood that?

Hey everyone ! i've been pretty busy for the past couple of days and i've come up with a new design . This entire thing i'm doing is for my project for college .

Well first off i've come up with a new design .

The design i used as a reference is contained in the link below

http://home.cogeco.ca/~rpaisley4/Stepper2012Unipolar.html

Now , from this design i have chosen to implement the following changes .

Instead of using transistors i'm choosing to use 4 N channel mosfets (NVTFS5811NL) 40V,40A in H bridge configuration to drive each coil . I'm designing the circuit for a 4 phase motor ,hence 4 coils are needed .

To control the current ratings i've chosen to use A current sensing IC (ACS711) to limit the current to 20A .

Now as per the design in the link above they were using a shift register and a 555 as clock , and i'm choosing to replace both of these with a PIC18F452 Microcontroller so as to ease the circuit . As for why i'm fixated with 20 A

P=V*I

As i only want a 12V source ,i need 20A to get 240W of power .

The main goal of the project is to create a universal driver that with a low voltage and high current rating , gives a good power rating .

I hope i have been able to explain as clearly as to help you all understand better .

Any comments/ suggestions are most welcome .

Now i wish to design this circuit and i was thinking of using LTSpice . Does anyone have any suggestions as to whether i should continue with this implementation or opt for another software ?

I hate to say this, but I think you have/will bite off far more than you can chew....hopefully not!

Swapping out components is a job for a well trained person in electronics with access to good test equipment and the full knowledge on how to use it.

It is still full of pitfalls for the unwary....

You still haven't told us much as to why and what, so it will be basically impossible to help you (though I do wish you help from someone (anyone!) better "trained/knowledgeable" than I am, really!).

My questions are based around the following points which I believe are still unanswered (my apologies if I have overseen something already stated!):-

1) What are you trying to achieve? Full details. What is it for?

2) What type of motor(s) do you have available? (Full details please)

3) Please explain the reason you are so set on 20 amps?Why 240 watts of power?

We all understand why 12 volts, you explained...not that its a good idea though as far as I can tell with the limited infos.....I need to be convinced on that point further...

4) Do you realise that this circuit you are going to use (http://home.cogeco.ca/~rpaisley4/Stepper2012Unipolar.html), CANNOT be connected to anything else as it stands? That all you can control is direction and (very limited) speed, USING YOUR OWN FINGERS! THERE IS NO PC INTERFACE OR SIMILAR!!! Its a fun circuit for an experimenters only.....a simple DC motor could do basically the same with far less complication!!

To help you further, I personally will need a FULL disclosure from you. Leave no details out. Its the only way to make helpful progress I feel....

Please look back, I have posed similar questions more than once, few answers have been given......

I wish you well and full success.....but if you REALLY want to "do your own thing", then go and do it......you don't need me/us then......if you know what you want, simply do it!!

First, you are mixing terms in ways that prove that you do not understand what you are doing. To drive one coil with a true H bridge topology requires four transistors as can be seen here.

[To see where this schematic came from just click on the schematic.] This circuit is for driving a single coil DC motor. To drive independently all four of your coils with a true H bridge will require sixteen power transistors. It will be easier to do this with both P and N channel devices but it can be done with just one type. If you had looked at the data sheet for the half H driver chip [SN754410] you would see that your template circuit is not using all of the designed attributes of this robust chip.

I suspect that your eight wire motor is not really a four phase motor, too. There are four coils but they are more common to be two A coils and two B coils. In other words a four coil two phase motor. Without a motor part number or reference I cannot tell what you actually have.

My point here is that you are repeating words without comprehension. You are doing yourself and your schooling a great disservice.

GA 4 U!!

He is making little sense to me also.....thanks for the support.

I almost forgot. With 20 amperes of drive current, you will probably have a problem with the self heating in this surface mount only MOSFET. I know the Rds value for this transistor is a superb 0.006 ohms but the wiring and coil resistance working with the yet to be identified stator inductance value will cause Vds to not be zero for all of each pulse. These transistors may overheat. Oh, do you have the fabrication technology to use a surface mounted transistor?