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  1. #51
    Quote Originally Posted by dazp1976 View Post
    Was at least 5 years ago when I was advised against using the bottom connectors for 5v. Told it's more ideal to modify a usb lead instead due to the protection circuitry.
    Trying to re-find information on the net is a pig.
    Not sure I'd trust that information. I wouldn't trust USB for a CNC machine, not even to provide 5V as it's notorious for dropping out. The PSU would be protected by it's own circuitry and if the BOB as protection built into the USB connection which isn't on the 5v terminal then I'd take the risk for the sake of 5. I'd rather have it blow up than keep cutting out thru power dropouts while cutting, Only takes one job and you've lost far more than 5.

  2. #52
    Quote Originally Posted by JAZZCNC View Post
    Not sure I'd trust that information. I wouldn't trust USB for a CNC machine, not even to provide 5V as it's notorious for dropping out. The PSU would be protected by it's own circuitry and if the BOB as protection built into the USB connection which isn't on the 5v terminal then I'd take the risk for the sake of 5. I'd rather have it blow up than keep cutting out thru power dropouts while cutting, Only takes one job and you've lost far more than 5.
    It's worked so far taking 5v from a small switched psu into a usb cable. However. I might change it round now you've convinced me on it.
    If I can make enough money I'll be swapping to an ess and get a new BoB rated for 200+khz asap for axis control anyway. My current board will go to run spindle/ limits/ estop etc. Well that's once I pluck up the courage to tackle the spindle wiring
    Last edited by dazp1976; 08-04-2020 at 02:10 PM.

  3. #53
    Quote Originally Posted by JAZZCNC View Post

    To be honest, if you are going to start again with a new controller and drives then I suggest you trace wires and label them, then rip out everything else in the control box and start afresh. It's often quicker more reliable and less confusing.

    If you inventory what you have and find the voltages etc and tell me what controller you are going to use I will happily help you work out a wiring schematic.
    Ripping everything out sounds good to me but in the meantime while I get al the bits together I have taken up Doddys offer of a 36V power supply which I want to put on the Z axis to run the machine. I have foud four wires in the controller for the X Axis stepper but the stepper has 6 wires and they arent shown on the Denford wiring diagram for the umbilical connector from controller box to machine.

    Here are pics of the 2 relays on the rail:

    https://lozharroplures.co.uk/my_images/14.jpg
    https://lozharroplures.co.uk/my_images/15.jpg

    Much appreciate the offer of a wiring diagram.
    I have been speaking to an old friend who is electrical savvy I can use two of the toroidal transformers that I linked to earlier in parallel to get 600Va.
    I intend to use an AXBB-E motion controller and UCCNC and the drivers linked to earlier (unless you know any better options)
    I have these transformers:
    24V 3A
    24V 14.6A
    12V 2A
    And there is an RFI Filter already fitted to the mains input

    E-Stop will suffice on the big red button only.

    Anything else you need let me know

  4. #54
    Doddy's Avatar
    Lives in Preston, United Kingdom. Last Activity: 9 Hours Ago Has been a member for 6-7 years. Has a total post count of 805. Received thanks 129 times, giving thanks to others 34 times. Referred 1 members to the community.
    Just to be pedantic: You've shown a number of power suppliers - not transformers (there's a subtlety in the wording there). I'd hold onto the 3A PSU for services and sensors, and supplement it with a new toroidal transformer for the drivers. Possibly hold onto the 12V depending on what it's currently used for, but it would make sense to rationalise the cabinet as far as is practicable, if for nothing else other than ease of maintenance). Your friend's suggestion of using two toroidal in parallel - broadly speaking, yes, but you're getting little benefit than using a single big one, unless you already have access to these? (or are looking to increase in future?, possibly just provision for the space of a future toroidal? - might make sense). I'm not quite sold on wiring two transformers in parallel that might have a different manufacturing tolerance - you could end up pumping some power from one transformer into another, but the power involved might be lost in the noise.

    Your choice of 36V for the Z? - the original idea was to understand if the increased voltage improved your most susceptible axis. But that's your call and your game - leave you to it. I'd recommend replacing with the BFG toroidal transformer in the future.

    Steppers with 6 wires?, measure the resistance between these - three will be (likely) connected to each coil - centre tapped, you probably should connect between the two wires of each three that has the greatest resistance (example you might find A-B = 1.5R, B-C = 1.5R, A-C = 3R, connect to A-C)

  5. #55
    Quote Originally Posted by Doddy View Post
    Just to be pedantic: You've shown a number of power suppliers - not transformers (there's a subtlety in the wording there). I'd hold onto the 3A PSU for services and sensors, and supplement it with a new toroidal transformer for the drivers. Possibly hold onto the 12V depending on what it's currently used for, but it would make sense to rationalise the cabinet as far as is practicable, if for nothing else other than ease of maintenance). Your friend's suggestion of using two toroidal in parallel - broadly speaking, yes, but you're getting little benefit than using a single big one, unless you already have access to these? (or are looking to increase in future?, possibly just provision for the space of a future toroidal? - might make sense). I'm not quite sold on wiring two transformers in parallel that might have a different manufacturing tolerance - you could end up pumping some power from one transformer into another, but the power involved might be lost in the noise.

    Your choice of 36V for the Z? - the original idea was to understand if the increased voltage improved your most susceptible axis. But that's your call and your game - leave you to it. I'd recommend replacing with the BFG toroidal transformer in the future.

    Steppers with 6 wires?, measure the resistance between these - three will be (likely) connected to each coil - centre tapped, you probably should connect between the two wires of each three that has the greatest resistance (example you might find A-B = 1.5R, B-C = 1.5R, A-C = 3R, connect to A-C)
    Sorry for the incorrect terminology. I won't be throwing anything away and the 12V was for the V5 Spindle controller which isn't used.
    Z was a typo should have been X

    I have discovered the coils are centre tapped and I know which are which, my problem now is finding out where the tap leads go to.

  6. #56
    Quote Originally Posted by ngwagwa View Post
    I have discovered the coils are centre tapped and I know which are which, my problem now is finding out where the tap leads go to.
    They don't go anywhere just terminate them so can't short.

  7. #57
    Doddy - I was advised using two identical toroidals in parallel would be OK if they were identical units but warend against using different suppliers/models. I was looking at going that way as I have been unable to find a single unit with the required output - have you any suggestions?

  8. #58
    Quote Originally Posted by JAZZCNC View Post
    They don't go anywhere just terminate them so can't short.
    On the machine side I can't get to them inside the cabinet (short of cutting them where they enter the stepper). According to the Denford documentation they do not connect to the umbilical. I will look if I can see them on the underside of the machine tomorrow.
    Just before I left the workshop I was reading somewhere that was saying depending what you do with the tap wires will give more speed or more torque but I can't seem to find it now, my . laptop must be as forgetful as me.

  9. #59
    Doddy's Avatar
    Lives in Preston, United Kingdom. Last Activity: 9 Hours Ago Has been a member for 6-7 years. Has a total post count of 805. Received thanks 129 times, giving thanks to others 34 times. Referred 1 members to the community.
    Quote Originally Posted by ngwagwa View Post
    Doddy - I was advised using two identical toroidals in parallel would be OK if they were identical units but warend against using different suppliers/models. I was looking at going that way as I have been unable to find a single unit with the required output - have you any suggestions?
    Sound advice from your mate.

    The 2x35V transformer that you linked suffers from being in no-mans land - wiring the secondaries in series will generate a DC terminal voltage of around 100V (outside of the range of the majority of stepper drivers and too high for the small steppers on the denford). In parallel they'd through out about 50V - too much for the cheap nasty stepper drivers and too low to exploit a decent digital driver effectively. It'd work, but it's not in the Goldilocks zone.

    Personally, if I was looking at CPC then I'd look at their 2x25V options (e.g. https://cpc.farnell.com/multicomp/mc...%20transformer) - wiring the secondaries in series to generate a 50VAC/70V pk DC terminal voltage for an 80V drive. Personally, I think 300VA would be sufficient but note the previous advice of giving yourself headroom with a 500w should you need to grow. Or parallel similar as your mate suggested.

    BUT, much depends on your choice of stepper driver. That's really your first decision point before speccing the transformer.

  10. #60
    Quote Originally Posted by Doddy View Post
    BUT, much depends on your choice of stepper driver. That's really your first decision point before speccing the transformer.
    I was considering these drivers https://www.cnc4you.co.uk/Microstepp...tepping-CW8060 JAZZ said they were overkill but would do. If you can suggest a better driver I am open to advice bearing in mind an earlier comment by JAZZ that if I needed to replace a stepper in the future it would likely need more power (or words to that effect).

    Also would these be right for use on your suggested toroidal transformer?
    https://cpc.farnell.com/on-semicondu...ngdom%2Fsearch
    and 4 of these in parallel
    https://cpc.farnell.com/multicomp/mc...9?st=capacitor
    Last edited by ngwagwa; 08-04-2020 at 04:24 PM.

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