Thread: 4x4 cnc router

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  1. #1
    Hi guys, i have considered building a cnc router for a while now so heres my build stage!
    i would appreciate any help on the electronics side ? as I'm am really lost here.
    take a look at the pictures and let me know what you think!
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  2. #2
    heres a few pics of the drivers :)
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  3. #3
    I'm not sure exactly how much help you need, but I'll try to be as clear as possible, and it may be a little basic.

    The Gecko controller will have a minimum of 3 wires going to the breakout box - unfortunately, it's a little unclear from the picture, but I did find this site, where they have a PDF of the wiring diagram.

    The three wires you need for each of the Gecko drive units are:

    - Ground
    - Step direction
    - Step clock

    These will need to go to the Gecko's "COMMON", "DIR" and "STEP" pins respectively. The jumper towards the middle of the board (labeled "COM TERMINALS" in the PDF) will need to be set to position 2-3 (rather than 1-2), because this will put the COM terminals to GROUND, rather than +5v.

    Look at the bottom of the board in the PDF, which is the top as you've taken the picture, for which is which - so, for the X-axis, you would use:

    "2 X Step" -> "STEP"
    "COM" -> "COMMON"
    "3 X Dir" -> "DIR"

    Y-axis:

    "4 Y Step" -> "STEP"
    "COM" -> "COMMON"
    "5 Y Dir" -> "DIR"

    I'll leave the other axes for you to work out

    The "DISABLE" pin can also come from the breakout board, normally a charge pump circuit - although I can't see an output for that in the PDF.

    You'll need a resistor across the "CURRENT SET" pins - the top-right corner of the Gecko box shows what you'll need (which will need to be matched to the motor you're using).

    The power supply should have two wires coming from that - these will need to go to the Gecko's left hand connectors (as you've pictured them). Make sure that the PSU ground goes to the "POWER GROUND" pin, and the PSU + supply to the "+18 TO 80 VDC" pin.

    Now, the motor - there's 3 basic ways in which you can wire it up. Most of the time, you want both power and torque, so you'd use a parallel connection (parallel will run the hottest).

    The colour of the wires is important, as they will denote which phase pin they need to go to. I think that most wire colours do follow the same standard, but I can't guarantee this. Each wire is used once, and are connected to another wire. Edited to add - I've just seen a better picture of the motor in the other thread (and the fact that it's from Zapp, which is where I got mine) - and this should be the same.

    The way I've wired mine up is:

    Yellow wire and black wire -> Phase A
    Blue wire and red wire -> Phase A'
    Orange wire and green wire -> Phase B
    Brown wire and white wire -> Phase B'

    (I've used Phase A' to indicate the Phase A with the bar above it).

    I took a picture of it while I was building my machine. The connector is arranged A, A', B, B' (from left to right).

    I think that should hopefully cover the basics. There are things I've omitted (such as power to the breakout board, and also power to the PSU), but they shouldn't be too difficult.
    Last edited by tribbles; 10-10-2009 at 11:14 PM.

  4. #4
    Hello

    thank you so much! i really didn't think anyone would help :nope:
    i was also wondering what type of slow blow fuse (amp) and holder i should use on the power side before the drivers ?

  5. #5
    I didn't use one, but generally you should base it on the current that will be consumed by the driver.

    So, if the output of the driver is 4A at 50V, then that's 200W (multiply the two together). Then, divide by the voltage input of the driver, say 100V. This means 2A.

    However, that does assume there's a 100% efficiency in the transfer, which there never is. I'd estimate between 75% and 90% efficiency, so worst case, it will be 2 x 100 / 75, or ~2.7A. Then choose the next value up from there (probably 3A).

    This is also applied to the power supply itself, so if you had 3 drivers with 2.7A@100V (270W x 3), then that would be 810W. Giving 220V into the PSU, you'd need a 3.7A, but with 75% efficiency, it's 4.9A - or say 5A.

    I'd probably be tempted to use a self resetting fuse - if anything goes wrong, just remove the power, and the fuse can be reused.

    As to the type of holder - really up to you.

    One thing though - if your motors are rated at 4A per phase, then wiring them in parallel will actually consume 8A, since in parallel, the current is doubled (you're putting two phases in parallel).

  6. The other thing you need to consider is what wire you connect drivers to power supply and drivers to motors with.

    Each driver should be connected seperately to the power supply, do not daisy chain them. An individual fuse in the feed to each driver is a good idea. It should be rated 50% higher than the driver output current - so for motors with a 2A phase running bipolar (4A per phase, 8A per driver) a 12A fuse is a good idea. It doesnt need to be slow blow on the driver side of the power supply. Either chassis mounted fuse holders, or the in-line automotive types will work well up to 16A.

    For a 2A phase motor wired bipolar (4A) you need at least 0.5 mm sq per core (typically 16/0.2 wire) - do not use single core house wiring cable, its not flexible and will crack under the vibration of the motor (in time). Ideally it should be screened wire... often you can find this on eBay listed as 4-core CY. 4-core 16/0.2 wire is good for 4.5amps (9 Amps derated 50%), above this you will need to use 24/0.2 wire which is good for 8A in 4-core form (although they are usually derated below this for indistrial applications). example

  7. #7
    Hi Guys

    thank you all, I'm going for the din rail type of holders (fuse)

    so for my motors....
    http://www.axiscnc.com/pdfdocs/sy85sth1184208a.pdf

    setting these up in unipolar (4.2) i have the 82K +/- 5% 1/4W Resistors which i think is just right for the drivers with the motor settings ?

    so am i right in thinking a 12amp fuse! i cant seem to find the trip style of fuse so should i still go with the slow blow 12amp glass fuse ?

    my driver specs are here http://www.geckodrive.com/upload/G203V-REV-7-MANUAL.pdf

    says something regarding 10amp short circuit trip protection

    so would a 10amp fuse be good before it gets to the drive ?

    oh i wish i was electrical minded!


  8. Quote Originally Posted by kingfisher View Post
    Hi Guys

    thank you all, I'm going for the din rail type of holders (fuse)

    so for my motors....
    http://www.axiscnc.com/pdfdocs/sy85sth1184208a.pdf

    setting these up in unipolar (4.2) i have the 82K +/- 5% 1/4W Resistors which i think is just right for the drivers with the motor settings ?

    so am i right in thinking a 12amp fuse! i cant seem to find the trip style of fuse so should i still go with the slow blow 12amp glass fuse ?

    my driver specs are here http://www.geckodrive.com/upload/G203V-REV-7-MANUAL.pdf

    says something regarding 10amp short circuit trip protection

    so would a 10amp fuse be good before it gets to the drive ?

    oh i wish i was electrical minded!
    The Motors you have are 8 wire...they can only be used in bipolar parallel or bipolar series with those drivers. So you have the choice of running at 6A or at 3A per phase. You can of course run them wired bipolar parallel at a lower current, e.g. 4A if you wanted but the only reason to do that is if your power supply wasnt up to the job. Your PSU is an 11A output. Ideally you'd want one per motor, or at least two in parallel. A single supply is going to limit you to a phase current of about 4.5A - 5A.

    These are hi-inductance motors, so wiring them Bipolar Series is going to severely limit torque at speed, so I'd still wire them Bipolar Parallel but run at a reduced current of 4.5A (82k resistors). You can always add a second or third supply later and up the current to 6A.

    The Gecko will shut down if you try to draw more than 10A from it. Fuses in the supply to the Geckos are additional protection in case of a catastrophic failure of the Gecko - to prevent wires melting and potential fire. They should be rated at 10 - 12A in this instance.

    The other consideration is that the Gecko need a substantial heatsinks for running at 5A - I think you have these and showed a pic of them in another thread?

    One word of warning:

    80v at 11A is potentially lethal (as is anything above 50v - which is why phone systems are all 50v). Keep hands away and if you have to adjust anything while its switched on always work with one hand in your pocket - that way you stay safe!
    Last edited by irving2008; 12-10-2009 at 12:50 AM. Reason: safety warning

  9. #9
    thanks guys


    right yes i will keep to these settings, Bipolar Parallel...4.5A with the 82k resistors! if i need to change setup at a later date then so be! (funds are running low)
    all the fuse gear is on its way also my steel cabinet to house all the parts.
    anyone on the wiring for the motors with the setting above (Bipolar Parallel)

    oh...please a link to some wire for the controller set up (in the box,power,drivers,breakout board) i have some shielded wire for the motors, I'm sure you guys know the best place to buy ?

    once again i cant thank you all enough and so glad i posted here!

  10. Quote Originally Posted by kingfisher View Post
    thanks guys


    right yes i will keep to these settings, Bipolar Parallel...4.5A with the 82k resistors! if i need to change setup at a later date then so be! (funds are running low)
    all the fuse gear is on its way also my steel cabinet to house all the parts.
    anyone on the wiring for the motors with the setting above (Bipolar Parallel)

    oh...please a link to some wire for the controller set up (in the box,power,drivers,breakout board) i have some shielded wire for the motors, I'm sure you guys know the best place to buy ?

    once again i cant thank you all enough and so glad i posted here!
    hookup wire for linking breakout to drivers and other low voltage stuff, use standard 7/0.2 equipment wire available from Maplins amongst other places. A good colour scheme helps with fault finding...

    For wiring power supply to drivers use the same wire as for the driver to motors. you will need a 4-way 10A connector block to transition from the 4-core wire to the motor wires.

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