Thread: Hi from Brum

  1. #1
    Hi all

    What to say, what to say (to skip the babbling you may want to skip to paragraph 6 :)) ........

    I have just got into the world of cnc and have little experience.

    I picked up a cheap (well cheap for this field) 6040 yoocnc knockoff from ebay. I thought this machine would be a means to an end but unfortunately I have been sucked into the cnc world which I am loving.


    I am planning to get some new gear to upgrade my 6040 as it's not very accurate and misses steps etc. I rewired the externals with shielded wire, re-installed windows as a standard pc and removed unnecessary services, this has helped...just not enough.
    I will mostly be working with hard woods such as mahogany and maybe even kamagong along with brass and aluminium in mach3.

    The upgrades will be as follows:
    1. Purelogic PLCM-E4 bob/motion controller (to remove my crappy parallel port from the equation)
    2. 3x leadshine em806 drivers
    3. 3x nema 23 3.1nm steppers.
    4. Power supply (and here comes the question!)

    I've done the workings for the power supply so I won't bore you with that unless asked for. I need a 57-63v (based on mH +/- 20%) 8.4amp linear power supply.

    Seems like a stupid question but I am going to ask anyway.

    Q1. Does the power supply need to have 3 sets of V+ and V- terminal or can they all be run from 1x V+ & 1x V- terminal?

    Q2. If they can be run from 1 terminal, does that mean that the 60v will be shared between the 3 drives?

    Q3. If each drive needs it's own terminals, will a PSU rated at 60w & 10A. deliver 60w & 10A to each V+ terminal?

    Any suitable PSU links would be appreciated.


    Thanks for any help.

    Mark

  2. #2
    Quote Originally Posted by smeg up View Post
    Hi all
    Q1. Does the power supply need to have 3 sets of V+ and V- terminal or can they all be run from 1x V+ & 1x V- terminal?
    They can all be run from 1x V+ & 1x V- terminal, that's how you wire them, each one uses it's own wires from the power supply to the EM806. What you have not got to do is loop from one to the other.

    Quote Originally Posted by smeg up View Post
    Q2. If they can be run from 1 terminal, does that mean that the 60v will be shared between the 3 drives?
    Each driver will see 60v

    Quote Originally Posted by smeg up View Post
    Q3. If each drive needs it's own terminals, will a PSU rated at 60w & 10A. deliver 60w & 10A to each V+ terminal?
    The current will be divided among them. Watts = current x voltage, so W will also be divided. In other words if you add up the currents and wattages of each driver the total should not exceed that of the power supply.

    Read this it explains it all and it applies to any system not just Geko; http://www.geckodrive.com/support.html
    Spelling mistakes are not intentional, I only seem to see them some time after I've posted

  3. The Following User Says Thank You to EddyCurrent For This Useful Post:


  4. #3
    Thanks Eddy

    I had a look at a different gecko document to get the voltage and amps but thanks for the link, I will check that out.

    I know not to daisy chain the drivers and will look into the wattages now but I thought the rule of thumb regarding the amount of amps provided by the power supply was 2/3 of the combined total of stepper motors.

    The steppers I want to use will draw a current of 4.2 amps each, x3 = 12.6amps so 2/3 is 8.4amps, am I totally wrong with this?

    Just looked at my post again, that was supposed to be 60v not w, whoops...

    Thanks

  5. #4
    Ignore the last post (which doesn't look like it displayed for some reason?), just read quickly through the document, I think I am on the right lines now but if someone could check I would be most appreciative, btw, the last reply I think I called you eddy, saw where your nick originates from now so apologies :)

    Working out PS.

    Running steppers in 2 phase bipolar parallel connection. http://cnc4you.co.uk/resources/Stepp...1B%203.1Nm.pdf

    1. AMPS - 3x steppers drawing 4.2 amps. 3 x 4.2 = 12.6A
    Because running in parallel amps required from PS should be 2/3 of total = 8.4A
    Q. I presume it is ok to up to 10A as the drivers will draw what they need?

    2. VOLTAGE - 32 * √L = Vmax
    inductange (mH) of 1x stepper is 3.2 +/- 20% so 2.56-3.84mH
    using the above, as far as i can see the voltage should be 51.2-62.71V or 57.24V if the stepper is spot on.
    Q. So would a 60v 10A PSU be correct? Do i need to multiply the volts by 3 for the other steppers?

    Thanks.
    Last edited by smeg up; 14-01-2015 at 06:46 AM.

  6. #5
    Quote Originally Posted by smeg up View Post
    the last reply I think I called you eddy, saw where your nick originates from now so apologies :)
    No, Eddy is fine everyone uses that.

    Quote Originally Posted by smeg up View Post
    1. AMPS - 3x steppers drawing 4.2 amps. 3 x 4.2 = 12.6A
    Because running in parallel amps required from PS should be 2/3 of total = 8.4A
    Q. I presume it is ok to up to 10A as the drivers will draw what they need?
    Yes, 10A will do fine, they will only draw the amps they need.

    Quote Originally Posted by smeg up View Post
    2. VOLTAGE - [FONT=TTE2325410t00][SIZE=3][FONT=TTE2325410t00][SIZE=3]32 * √L = Vmax
    inductange (mH) of 1x stepper is 3.2 +/- 20% so 2.56-3.84mH
    using the above, as far as i can see the voltage should be 51.2-62.71V or 57.24V if the stepper is spot on.
    Q. So would a 60v 10A PSU be correct? Do i need to multiply the volts by 3 for the other steppers?
    If you look at the EM806 spec. it says 68V typical, 80V max so I would use 60 volts as an absolute minimum.
    You don't multiply the volts by 3
    The best type of supply for this application is an unregulated 'linear' one and best to build it yourself, there are examples of how to do that if you search this forum.

    Here's one and the next post down too.
    http://www.mycncuk.com/threads/7942-...2015#post62015
    Last edited by EddyCurrent; 14-01-2015 at 10:17 AM.
    Spelling mistakes are not intentional, I only seem to see them some time after I've posted

  7. #6
    Great, I think I will go for a 70V PSU then as that works out to be a 500VA 2x25VAC Transformer.

    Thanks for all your help Eddy, just got to learn about transformers now......will it ever end :)

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