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  1. #11
    I'd forgotten that 410R resistor off of Q2. That makes sense.

  2. #12
    I didnt want to use a PIC at this stage because I havent used them before and didnt want to have to learn how now. Looks like I'm going to have too tho as I'm struggling to fit it on the 3" x 4" demo board in eagle

    So is the Burger cuircuit no good then, Sorry for being thick

    The orignal thead was [ame="http://www.cnczone.com/forums/showthread.php?t=44802"]Problems with stepper driver (L297 and L6203) - CNCzone.com-The Largest Machinist Community on the net![/ame] but as its 3-4 years old I didnt see much point in posting

    And the link is to a polish site, which obviously I havent got a clue what it says http://forum-cnc.pl/index.php?topic=55.0

  3. Quote Originally Posted by Ross77 View Post
    I didnt want to use a PIC at this stage because I havent used them before and didnt want to have to learn how now. Looks like I'm going to have too tho as I'm struggling to fit it on the 3" x 4" demo board in eagle

    So is the Burger cuircuit no good then, Sorry for being thick

    The orignal thead was Problems with stepper driver (L297 and L6203) - CNCzone.com-The Largest Machinist Community on the net! but as its 3-4 years old I didnt see much point in posting

    And the link is to a polish site, which obviously I havent got a clue what it says http://forum-cnc.pl/index.php?topic=55.0
    Yes I found that too... I couldn't find anything in English relating to the original design

  4. Quote Originally Posted by irving2008 View Post
    Yes I found that too... I couldn't find anything in English relating to the original design
    However a google translate on post #3 'version 2006.04.26' throws up:

    "
    • -circuit protection -> T1
      -reduction system DC ... after inactivity -> PIC
      Power-split
    "
    So that confirms what the PIC does... but no info on the code... I wonder if this was ever built?

  5. #15
    Dam I tried google translate and it came up with a load of rubbish.

    Do you think it might not be worth pursuing? I saw the first few designs that didnt have the pic so I presumed it would work without it but the idea of reducing the hold current sounds like a good idea given the buzzing and noise that I got last time.

  6. #16
    Unfortunately, without the code for the PIC, it'll be effectively useless - it would be possible to write something, but it would probably need a bit of tweaking to get it right.

    I'd be tempted not to use it at all and see how you get on. The motors would get hotter because the power will be on all the time.

    I like Eagle, but I got fed up of the small board size (which is their aim, I suppose), so I bought the professional edition in the end - which also gives multi-sheet schematic entry as well. I did manage to make a board wider than the maximum size, but I had to use vias for PTH pads, and be really careful about the positioning of the other components.

    I'm just having a discussion with Farnell (who bought CadSoft) about getting the autorouting package for it as well (I only got Layout and Schematic, but now I want to get the complete package).

  7. Shouldn't be too hard to create the same effect without the PIC. I see a monostable to define the timeout, and an astable with variable on/off ratio to provide a modulating switch. Could be done with the two halves of a 556 I reckon...

    Then again, why not just pull Vref down rather than modulate it?

    I will think on it...

  8. #18
    I think you'd want to modulate it in order to adjust the holding torque.

    But you're right - a 556 would provide the timeout and the reduction in torque. Although a 555 and a suitable transistor/resistor should pull VREF down to a suitable amount (much in the same way that Q2 does it).

    Hell, you may even get away with a simple RC timer - assuming the clock's quiescent voltage is 0. That I'd need to think about (analogue electronics isn't my forté).

  9. #19
    Thanks for the input, most appreciated.

    The mono stable and astable idea sounds good but beyond my capabilites so I will have to wait for your input
    I found a circuit that uses a 555 to pull vref down after 10s, its from a unipolar design that uses an L297 so i presumed it would be ok.

    I'm not sure if I fully understand the timing delay, I presumed that the control circuit would activate the lower vref so soon as the clock stopped? but looking at this I think it only works after 10s of inactivity. so in most cases the current will be full power?
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  10. Quote Originally Posted by Ross77 View Post
    Thanks for the input, most appreciated.

    The mono stable and astable idea sounds good but beyond my capabilites so I will have to wait for your input
    I found a circuit that uses a 555 to pull vref down after 10s, its from a unipolar design that uses an L297 so i presumed it would be ok.

    I'm not sure if I fully understand the timing delay, I presumed that the control circuit would activate the lower vref so soon as the clock stopped? but looking at this I think it only works after 10s of inactivity. so in most cases the current will be full power?
    The delay could be made adjustable, but that circuit would do the trick. It needs a lot more parts than the PIC, that is the attraction of using the PIC...

    I dont think a PIC program would be hard to create, using a 16F84 or equivalent...they are only a few pence now and programming them isn't hard (I can do it, so can at least 2 or 3 others)

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