Current Limiting For Stepper Motors

current limiter

[Ito-Brazil] pointed out N-Labs simple current limiter for stepper motors. A current limiting system will let you run stepper motors at higher speeds, with greater torque and efficiency without overheating. This particular design is meant to improve upon the common L/R and Chopper drivers. It can handle high voltages without using large resistors and is high performance without using expensive ICs.

51 thoughts on “Current Limiting For Stepper Motors

  1. Travis, it increases the torque, efficiency, and speed of a stepper motor. It’s useful. Stay tuned, maybe there’ll be another PSP mod to keep you happy come Monday.

  2. ok pocketbrain, since you seem to know exactly how this device works, would you mind sharing it with the rest of us (considering that the read link doesn’t work for the rest of us) I would especially like to know how this device increases the speed of a stepper motor, considering that the speed is controlled by the frequency at which the controller switches the windings at…

    And at jason, I am pretty sure that darkfader meant that this circuit is a lc filter, although by the looks of it I am thinking more on an rc filter (unless the motor winding is the inductor…)

    I would guess that it is a constant current source so that the windings always get their rated amount of current… But it is hard to tell from the pic… could just be doing just about anything…

    I want a working link!

  3. Still not getting through… Did the website get slashdotted or something?

    Chill Dave and Travis… It looks like steve has disappeared for the day so lets not ruin the vaguely mature, productive atmosphere.

    Anyway, @2, I’ve never done turntable design work but I was under the impression that a normal stepper could easily provide the nescessary speed/torque without putting this kind of circuit in between. I guess you could use a cheaper/smaller stepper maybe?

    Also, I would worry a little about putting more circuitry in the path… wouldn’t have the potential of slightly altering the incoming frequency thus leading to an innaccurate speed? Probably not a huge concern (I imagine any change would be pretty small) but coming from the paranoid world of DIY amp work, I know that little things can seperate a good project from a great one.

    But like I said, I’ve never done turntable design so maybe I’m missing something?

  4. Ok I started this in the PSP post, so let me finish it……

    I too am a long time reader of hack-a-day. I ENJOY this site for what it brings. What I said is not to put Eliot down, it is you guys who are doing that.

    As I mentioned, being a LONG TIME READER, I have seen the change in the amount of posts/hacks. Many other people voiced their “opinions” and most agreed with me. Not someone who likes to only read for a certain amount of time, or someone who likes the site the way it is because it works for them. We have been here longer and just because we can remember how good it was and you cant, doesnt give you all the right to start mouthing at us. It is your own opinion what you think of this site, I was voicing mine. You wouldnt go up to someone who believes in a different god and tell him that he is totaly wrong and he should get over him self? Thought not…

    If you like it or not, hack-a-day was once better than it is now. Tough luck, get over it. What I said should have been taken as inspirational critisism, and as a site owner myself I would have taken it as that. But instead Eliot has people seriously bringing this site down. Why are you all flaming people for saying what they think.. Should I tell you to shut up everytime you say something? Thought not…

    Also some one posted
    “If your not part of the solution your part of the problem”…..

    Well I like to think Im part of the solution, I have offered a little insite, from a reader who actualy cares what happens to this site. Im not telling Eliot how to run his site, you lot are by telling people like me to shut up. You are part of the problem by putting people down. The comments should be a friendly place, not a place where you get to shout at everyone. Whats the matter? Doesn’t Eliot want any inspirational critisism? Are you going to be telling him when to go to bed next, so he can be properly rested for work on the site? Thought not…

  5. If I wrote a ban comments script, would hackaday use it.. I’m sure it’d be so popular that it would even be the hack of the day…

    In short PLEASE hackaday, for the mental health of the hackaday community would you add some kind of ban to AT LEAST the comments and ban stupid people for a few days, or a month, etc… Cmon even hackaday owners know that most of these hacks are worthy of kudo’s which they dont get from a large portion of the community…

    As for the hack, good work, i’m not an expert on motors or electronics in general but I know for it to be hackaday’d it’d have to be good =)


  6. @Fragged: Would you mean to ban me? Once again are you saying that my opinion, and my thoughts are not welcome here? That is not your choice to make.

    My posts arnt bad, its the people using offencive language that do bad posts. If you all cant see that my posts are inspirational critisism, and you take them as being bad, then that is your problem. Im sure Eliot would see it a different way.

  7. >Anyway, @2, I’ve never done turntable design
    >work but I was under the impression that a
    >normal stepper could easily provide the
    >nescessary speed/torque without putting this
    >kind of circuit in between. I guess you could
    >use a cheaper/smaller stepper maybe?

    For DJ work -particularly scratching, torque is king. All new ‘tables are sold on the strength of providing more sustained torque than the previous model and so forth. Classic models don’t tend to use steppers although newer ‘tables do.

    I did some mod work on the Tech 1200 to increase the torque by bridging the limiting resistors to the windings using secondary resistors. It definately worked, but I got small wavelike fluctuations in the speed (particularly startup and stop), so I restored everything to stock and

    >Also, I would worry a little about putting >more circuitry in the path… wouldn’t have >the potential of slightly altering the >incoming frequency thus leading to an >innaccurate speed?

    Good point. when DJ’ing, any small fluctuation in the pitch can ruin a mix. Fortunately if you’re an experienced DJ, you can handle these things (some of us grew up mixing on Numark belt drives); but all that time spent correcting a bad mix could be spent cutting and scratching

    Come to think of it, I’ve done numerous mods on my 1200’s, I should write a couple up…

  8. Thought:

    Who else is more bothered by the volume of “if you don’t like it, shut up” posts than the posts by ignorami like Steve? I’m not too bothered by the idiot comments, it’s when otherwise seemingly intellegent people are drawn into rather silly and pointless debate that I get wound up.

    I live very near Sunderland. Someone pass me on Steve’s IP address so I can make hundreds of throwies and cover his house

    I’m sure he’ll appreciate it… in fact if anyone can furnish me with the required info I’ll make them spell out ‘hackaday’ and post a youtube link ^_^

    Keep up the fine work Elliot, I’m in awe of your consistent effect. 365 fresh hacks a year is no mean feat.

  9. @Mentor: Firstly thanks for not going over the top. Your reply was more like the reply I was hoping for the first time (in the PSP comments).

    I didnt say I AM the solution, I only said I would like to think I am PART of the solution, as I would think the whole community is part of the solution. Im sure Eliot would want feed-back from the whole community, not just a single person. I realise the comments arnt exactly a good place to discuss this (it should be for the project posted), for this I am sorry.

    As for me not saying what I thought would improve the site.. well…

    When I first started coming, as I said there were many projects posted per day. I enjoyed looking at different projects each day. If there is more posted, then Eliot can be sure there is something each person is going to really like. I also liked it When instead of doing 1 post for 1 project, he did 1 post for lots of projects and just gave the links to these (and a slight bit of info).

    This is only my opinion, Im sure everyone else has there own opinion, but please dont put me down because I am thinking this. Everyone is entitled to there opinion, and once again, Im sure Eliot would like the feed-back of all the users.

    If I just email him, then he will only have mine, but if he checks the comments then he can read everyones.

    Thanks Mentor

  10. Although, if I was him, I don’t think I’d bother reading the comments most of the time, for all the “first post” garbage and people heaping derision on a project they haven’t even been able to look at yet.

    For what it’s worth, I think this particular one looks worthwhile, and I’ll be keeping an eye on the site until it comes back up or a mirror appears.

  11. @dangel

    ok so basically what you want is more hacks per day. I can totally understand you and support that but as far as I can recall elliot made clear a long time ago that he will stick to the one hack one day scheme, because it was better/easyer(don

  12. Yall are dead wrong about this. Its not a power supply. Nothing in the article even suggests it to be a power supply. Thoes to-200 ic’s are not voltage regulators. They are most likely darlingtons. Your typical microcontroller can only source or sink a small ammount of ma. The purpose of this circuit is to allow a small ammount of current controll a larger ammount of current, for the purposes of driving a stepper.

  13. ^^ sorry, but you’re also dead wrong. the ic’s are in fact voltage regulators (a simple google would’ve told you that). however in this case they are being utilized as current regulators, which is a fairly common alternative application for those chips.

    this is also more than simple current switch to allow microcontrollers to control a stepper. the predominant method of deriving increased performance from a stepper is to use a much higher voltage than the motor is rated; this allows the magnetic fields to change more quickly, resulting in faster step stransisitions and torque. however, you can’t escape from ohms law, so if you modify the voltage you also have to control the current. there are dedicated ics for exactly this task, but they are relatively expensive and not as commonly available for the hobbiest. that is the purpose of this circuit.

    so while it is nothing groundbreaking, it is nonetheless a clever solution.

    and boy it seems a bunch of folks here are suffering from ibs sor something.

  14. ? wow, i thought i was pretty civil, but apparently i hit an ibs nerve.

    did you even read the page? the operation of the circuit is explained and the ic #’s are provided. are you asking me to hold your hand while we type the ic numbers into google? (besides the fact that lm317 is only like the most common variable regulator ever, you get an f for failure to identify a chip so common radio shack even sells it).

    you have me at somewhat of a disadvantage regarding the inputs, as i can only access the text of the article through google’s cache (the schematic images are missing). however, having designed and built several avr stepper projects, i can tell you that a darlington pair (which is really just a fancy bjt transistor, and mosfets are better suited anyway) controller would be next to useless… the whole point is current limiting. besides, there are either other connections on that board, or it is only a current regulator (2 in, 2 out) and requires additional switching devices for the motor. most steppers require 4 control terminals, whether they be unipolar or bipolar.

    now, my 1st post didn’t insult you, so i’m not certain of you current atitude other than possibly some type of inferiority complex. at least i’ve based my opinions on facts and article references, i see nothing but wild speculation from your pov.

  15. Pardom me for jumping in here but is anyone acctually connecting to the page? I’ve tried from home and work with different browsers and still get the can’t display errors. I have to say to N-Labs, WTF!

  16. Tell me how you would get the desired effect from 2 voltage regulators, 3 caps, 2 resistors. Good luck. Thoes are darlington pairs, but what the hell do i know, i just design circuitry for a living.

  17. Well, i finally got the cached oage to load. And damn, agent420 is right. Thoes are in fact voltage regulators. Guess im the one who needs to goto school ( and learn more about steppers )

    Sorry dude!

    My apologies.

  18. it’s cool ;-)

    The page is still down, so I still can’t see the schematic. But that board is just a twin current regulator for the 2 sides of a stepper. You would still need another transistor or h-bridge switching board to control the phase power.

    But what that board allows is the use of a higher voltage than the motor is spec’d for to improve performance. Earlier in this thread there was a comment wondering how that could make the motor faster because he suggested it was the phase logic speed that controlled the motor. Certainly, that is true. However, at some point the physical mass of the motor prevents it from keeping in step with increased switching logic speed, and you lose torque or it stops. Using some type of current regulator (like the board here) allows the use of higher voltages, which as I stated earlier results in the magnetic fields changing more quickly. This pushes the performance envelope up a notch.

    This theory and some examples can be seen at:

    ‘School’s been blown to pieces’… Alice Cooper

  19. This post shouldn’t even be here. The guy’s website’s been down forever (obviously has no idea how to setup a wiki or website).

    Also, it’s a very old concept (I’ve seen such circuits even in ECG books from 15+ years ago – if not more). Whoever claims to design circuits for a living and hasn’t seen this… Well, we know for sure you don’t do this for a living.

    And about the site being down, perhaps it’s a good thing. Try looking at the google cache. My english sucks, but this is beyond ridiculous!

    Random quote:

    “But higher voltage needs much higher resistor wattage, becaming the system obsolete, uses much current on transformer without get more performance”

    Worst english EVER… And he’s “releasing” his old/obvious/trivial circuit under creative commons – ROFL! Like it matters… Next article he writes he’ll license his flashlight circuit under CC too. He better not see you sell a flashlight, or his lawyers will contact you ;)

    this guy has *no* clue.

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