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  1. #31
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Current Activity: Viewing BUILD LOG: 3 Axis CNC router Has been a member for 9-10 years. Has a total post count of 1,833. Received thanks 192 times, giving thanks to others 5 times.
    It's quite amazing what can be done with logic chips, however I'm like you Ian, I'd be using software and I'm eager to see what Irving comes up with.
    Most of the early Gecko drives relied alot of pretty basic Logic chips, yet Marriss managed to do some pretty cool things with them.

    Assuming Dean doesn't require to move the exact number of steps/pulses, then you wouldn't have to be that accurate about timing, and could miss some pulses.
    For example, as soon as a pulse is input, output x pulses at a slow rate, then if another input arrives before the x pulses are generated, reset the counter to x and increase the output frequency and so on. That way you're never really behind the curve in terms of number of output pulses, and you don't have to handle buffering/predicting what's going to happen. Off course slowing down is pretty easy, however you may want to implement some kind of deceleration so you're not slamming to a stop as soon as you stop spinning the MPG from high speed.

    And from there, you could also add a logarithmic style input, in that the quicker you spin the MPG, the higher the step multiplier is i.e. slow turn could be single step, gradually increasing to 50x at high speed. That way you can still maintain accurate slow speed, yet still move at high speed.

    I could probably throw some code together, however I don't have any MPG to try it, and I've also currently not got any spare Arduinos kicking around! (I keep meaning to order some, as I've got a couple more prototypes to build, but that's currently on the roundtuit list!)
    Avoiding the rubbish customer service from AluminiumWarehouse since July '13.

  2. #32
    ...and the only reason that the Arduino-based approach fails to meet the cost criterion is because people think of buying a complete Arduino board. But an Atmega chip only costs a couple of quid (for one of the smaller dual-inline versions) and if someone could develop the code and burn the odd chip or two, it would barely cost more than a 555 with a couple of switches and a pot. In fact, it's the reason that the simpler microprocessors were developed in the first place, to avoid boards full of logic chips. I took this approach recently with a soldering iron temperature controller, but I have too many projects on the go already to put my hand up for this one, I'm afraid. So, watching with interest to see what turns up!

    Ex-G8BYK, now G4FBN, and wondering how it would have been done in thermionic valve days...
    Last edited by Neale; 25-04-2014 at 05:55 PM.

  3. #33
    The more I think about this - the more crazy it gets. A MANUAL pulse generator is exactly that - MANUAL. It allows you to step ONE pulse or MANY pulses under precise MANUAL control. That's it's whole purpose in life.

    Earlier, with an electric drill attached. That makes it no longer MANUAL. The MPG became a means to an end. When you pulled the drill trigger, you might just as well have turned a pot.

    The MPG is just becoming a distraction. Everything that everyone has suggested (even Irving with the ONE pulse per rev) is battling against the MPG's natural behavior. Whatever ANYONE comes up with it will no longer behave like an MPG - so why have it in there at all?

    I reckon your back to the 555.

    Sorry - short and to the point - I'm drinking here...


  4. #34
    Isn't it more obvious to use not electronics but a mechanical step-up?

  5. #35
    The standard circuit to multiply a frequency is a phased locked loop and there are ICs that implement it. If I recall correctly they don't handle varying frequency well.

    Quote Originally Posted by stirling View Post
    When you pulled the drill trigger, you might just as well have turned a pot.

    The MPG is just becoming a distraction. Everything that everyone has suggested (even Irving with the ONE pulse per rev) is battling against the MPG's natural behavior.
    Not everyone - I suggested the pot. back in post #13... However Jazz said he 'would like to keep the detent control of MPG', i.e. be able to move a distance specified by turning the dial, not just set it at a speed and go. Either are easy to do with a microcontroller. The differential signalling very slightly complicates matters. I just suggested Arduino as although I dislike them, it's undeniably easy, but in post #14 Jazz seems to call that a 'massive electronics project'...

    In software it is trivial - just stay one pulse behind, measure time (t) between pulses and output pulses at f=n/t where n is 10,20,50. If another pulse not received, output n pulses at your favorite frequency to catch up. But as Irving pointed out 'Dean wanted a learning experience too'.

    Quote Originally Posted by JAZZCNC View Post
    To be honest I'm little surprised( slightly dissapointed) there are not more takers or more informed/detailed suggestions because I know there are plenty on here who do know how or could easily come up with something.!
    It's more entertaining to watch and see what other people come up with. Plus I'm busy at the moment with another massive electronics project , so you'll hear from me if this isn't over in a month or two.
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  6. Tbh my approach just generates n pulses for each wheel pulse at a rate that's fast enough to finish before the next wheel pulse. To vary the multiplier pulse rate to adapt for the wheel pulse rate is much more complex and I'd probably start going the software route on that (but not beaten yet). I'm assuming Dean is just testing basic motion and maybe home/limit switches. I haven't provided any acceleration control - it's only 3 chips after all (optional 4th if you want an LED to warn of overrun, ie wheel pulses too fast for multiplier), plus 2 options for multiplier control, a dip switch giving 1 - 256 or a 4 way rotary giving 1, 10, 20 & 50

  7. #37
    This might not be what Jazz needs for his project but it might be useful to someone else. https://neil.fraser.name/hardware/stepper/ttl.html

  8. #38
    Quote Originally Posted by Jonathan View Post
    It's more entertaining to watch and see what other people come up with. Plus I'm busy at the moment with another massive electronics project , so you'll hear from me if this isn't over in a month or two.
    ROTFLMAO - Effing unbelievable - That has to be one of the most effing arrogant statements I've seen you come up with to date. It's a doozy.

    Hopefully the "entertainment" you get from watching the rest of us neanderthal cretins struggling with the concept of which way is up for one or two months meets with your approval.



    Ah thanks Matey - you kill me.

  9. #39
    Quote Originally Posted by stirling View Post
    Hopefully the "entertainment" you get from watching the rest of us neanderthal cretins struggling with the concept of which way is up for one or two months meets with your approval.
    I agree with Jonathan. Patently you don't understand what it is to be a geek.

    From a geek perspective this is a request for a magic box of tricks that performs some nebulous function with a motor by reading Jazz's mind when he plugs it in.

    If you think you can make it then you are either an extreme geek or a Neanderthal cretin. There is no middle ground
    Last edited by Robin Hewitt; 26-04-2014 at 04:33 PM.

  10. #40
    Fit a hand crank to the rear stub shaft of the stepper motor.

    Click image for larger version. 

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    Last edited by EddyCurrent; 26-04-2014 at 01:08 PM.
    Spelling mistakes are not intentional, I only seem to see them some time after I've posted

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