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  1. #1
    After a two plus year hiatus I've finally found the time to return to work on my Fehlmann CNC.

    I've also decided to go with LCNC as I really wasn't at all happy with Mach3. At the moment I'm going to use the stepper motor set-up that I have, but at some point I will switch over to servos.

    Clive S has been extremely patient and generous with his time and I think has answered most of my questions, but I just wanted to canvass this forum as to opinions about the relative advantages and disadvantages of using ethernet Mesa boards - I was thinking of the 7i76e - over PCI based set ups - 5i25 with a 7i76. The former set-up seems more straightforward and more flexible to me, but I'm just wondering if it's more problematic in some way.

    David

  2. The Following User Says Thank You to Agathon For This Useful Post:


  3. #2
    relative advantages and disadvantages of using ethernet Mesa boards - I was thinking of the 7i76e - over PCI based set ups - 5i25 with a 7i76. The former set-up seems more straightforward and more flexible to me, but I'm just wondering if it's more problematic in some way.
    Both of the above will give you the same results. 5i25+7i76 is for pci for the pcix you would use a 6i25+7i76 these two setups require a DB25 cable to connect the two cards together. ie quite a short distance.
    .
    The Ethernet versions means you can have the PC any distance (less than say about 90mtrs) from the control box with a cat5 cable.

    Ethernet versions are 7i76e with spindle control, 7i96 without spindle control ie. no 0-10v, These two cards don't require another BOB.


    Ethernet 7i92 does require another BOB as there are no opto's on it but a cheap bob can be plugged into it.

    I have used all of the above apart from the 6i25.

    If you decide to use servos in the future you can plug another card like a 7i77 for analogue or 7i85 step/dir both with encoder feedback, into any of the above cards.

    Edit: TheLinuxcnc version to go for is 2.8 or 2.9 as 2.7 is getting to EOL and things have changed a bit from 2.7 to 2.8

    Please note Linuxcnc is a learning curve, I am no expert but I have done a few conversions with Lcnc.
    Last edited by Clive S; 20-01-2020 at 01:18 PM.
    ..Clive
    The more you know, The better you know, How little you know

  4. #3
    Thanks again Clive, I'm inclined to go along the 7i76e route as it's a bit more compact and can be quickly plugged into different computers.

    I take it that only inputs required for this board are the ethernet cable and a 5v power supply? My set up will be using conventional mechanical limit switches, VFD for spindle speed, 3 stepper motors.

    It looks like this board can handle a great deal of limit stops - which I may want to try and handle the strange way the vertical axis of my machine can be positioned.

    David

  5. Ethernet and a field supply (something around 6V-34V - but check the manual!!!) - you can derive the 5V for the logic from the field supply.

  6. #5
    Thanks Doddy - do I need a field supply if I'm not using proximity sensors?

  7. #6
    Quote Originally Posted by Agathon View Post
    Thanks Doddy - do I need a field supply if I'm not using proximity sensors?
    Yes. Always RTFM and check any jumpers on the board

    Remember the Mesa card can handle 24V for the limit's which is better for noise regection
    ..Clive
    The more you know, The better you know, How little you know

  8. #7
    Ah OK, the 24v is to run the FPGA. A nuissance since I only have a spare 36v regulated supply and the only other 24v supply in the cabinet is AC and unregulated.

    Maybe the 5i25+7i76 is a better option afterall.

  9. #8
    Quote Originally Posted by Agathon View Post
    Ah OK, the 24v is to run the FPGA. A nuissance since I only have a spare 36v regulated supply and the only other 24v supply in the cabinet is AC and unregulated.

    Maybe the 5i25+7i76 is a better option afterall.
    You still need field pwr with the 7i76. Is the 36v supply for the steppers if so don't take field pwr from that.
    what is the 24v AC used for? You could add a rectifier and a cap.

    how about https://www.ebay.co.uk/itm/MDR-20-24...QAAOSwbl9dML~L
    or
    From the UK https://www.ebay.co.uk/itm/20W-Din-R...8AAOSwm5NeGD1b

    Edit: You could use 12V field power but if you might go with servos later then 24V would be more suitable.
    Last edited by Clive S; 20-01-2020 at 04:06 PM.
    ..Clive
    The more you know, The better you know, How little you know

  10. #9
    Right... I began to realise that I'd need 24v in either case shortly after posing.

    The 36v regulated supply was bought for this project, but was abandoned in favour of a home built heavy duty power supply, so would be dedicated to supplying the Mesa board - but isn't 36v too high anyway, I think the manual says 32v?

    I think one of those little DIN rail supplies would do nicely and so much less hassle than rectifying the 24VAC. Is 1A enough to do everything? Thanks for the links.

  11. #10
    Quote Originally Posted by Agathon View Post
    Right... I began to realise that I'd need 24v in either case shortly after posing.

    The 36v regulated supply was bought for this project, but was abandoned in favour of a home built heavy duty power supply, so would be dedicated to supplying the Mesa board - but isn't 36v too high anyway, I think the manual says 32v?

    I think one of those little DIN rail supplies would do nicely and so much less hassle than rectifying the 24VAC. Is 1A enough to do everything? Thanks for the links.
    When I refired to the 36V I was thinking using a DC -DC buck converter. Yes 36V is too high I would not go above 24V.

    2A is nicer.

    https://www.ebay.co.uk/itm/MDR-60-24...813c8b4bf5650c

    or
    https://www.ebay.co.uk/itm/Din-rail-...cAAOSwxlxd3f2c
    ..Clive
    The more you know, The better you know, How little you know

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