Build Thread microCarve A4/Gecko G540


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Thread: microCarve A4/Gecko G540

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    Default microCarve A4/Gecko G540

    I'm another proud new owner of one of John's (microcarve) microCarve A4 machines. I'm using it with a Gecko G540 motor driver, 48V linear power supply, and KL23H276-30-8B motors purchased from Keling.

    The items from Keling arrived last Tuesday, the A4 came on Thursday. Everything arrived in great shape. The packing job John did on the A4 was superb. The painted boards were wrapped in tissue paper, the table slide was in its own inner box marked "Don't Drop!"

    I set up an old PC with EMC2 last week, it'll be the dedicated controller for the system. I considered mounting the power supply and Gecko inside the PC's cabinet, but since I'm not familiar with what sort of heat I'd get off the power supply and Gecko I decided to put them into their own case.

    I decided to re-purpose an old UPS case I had hanging around in case it was ever needed:



    I decided to mount the Gecko into the back panel in place of the holes for the prior power plugs:





    At this point I'm doing the wiring of the power supply, cooling fans, and the Gecko. Once that's done, I'll be checking out the computer + Gecko, then hooking up the motors.

    When I'm taking a break, I'm personalizing the A4 a bit. Here's a sort of "before and after" shot of the side boards of my A4 showing what I do when I'm not in the shop:



    You can see more detail about what I'm up to with the build (like shopping for nibblers) at my blog:
    An Infinite Number of Cats on Keyboards

    and I'm on the microCarve Yahoo! Group.

    Enough posting for me...now back to work!

    Similar Threads:
    http://saundby.com/cnc --my website
    http://catsonkeyboards.blogspot.com/ --my blog


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    I have a 900vac APC case that I was going to use for my G540 and my steel channel machine when I get around to the electronics part of the build. You beat me to it.

    I like your choice of colors and paint work. Looks nice. Will follow along.

    CarveOne

    CarveOne
    http://www.carveonecncwoodcraft.com


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    Quote Originally Posted by CarveOne View Post
    I have a 900vac APC case that I was going to use for my G540 and my steel channel machine when I get around to the electronics part of the build. You beat me to it.

    I like your choice of colors and paint work. Looks nice. Will follow along.

    CarveOne
    Hey John, I just upoaded a new video for my Write2CAD program.
    Show how to make a G540 Panel for cnc.
    [nomedia="http://www.youtube.com/watch?v=lE9r_kKeZV4"]YouTube - G540panel.mp4[/nomedia]

    Bob
    CNC Projects



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    Nice job with the Gecko case and the paint!...



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    Quote Originally Posted by louieatienza View Post
    Nice job with the Gecko case and the paint!...
    Thanks!

    More progress today:



    Airflow cutouts for the power supply. I wasn't worrying about cosmetics here, just getting it "good enough". Airflow is my biggest concern with this case.



    I chopped the front off the original PCB to use the switch, a nice big red one. I left enough PCB to allow it to be secure in the original mounting hardware. It turned out that the switch could handle the AC current of the power supply, so I didn't have to use it to pull a relay or something. So I just cut the traces to the switch on the PCB then soldered the AC line wire to one of the N.O. contacts and ran a wire to the power supply's line input from the other contact.



    First power-up of the DC power supply. Everything's looking good at this point. I wanted to put in a power indicator LED. So I put a resistor divider/current limiter on the DC output. I made it for 10mA at 6VDC on a 48V source. This was a bit anemic for the bicolor LED that was already on the PCB, so I wired in a red LED that's daylight visible at 10mA and hot glued it in the old LED's place. It sits perfectly behind the light pipe in the front panel and looks great.


    The divider. The different colors of spade lug are on purpose. The bright one goes on the high side, the dark one on the low side. I put a thick layer of conformal coat over the exposed wires and a piece of shrink wrap over the top half after I took this picture. My conformal coat was Shelly Hansen's "Hard As Nails" clear, BTW.

    Tomorrow I'll finish by getting the fans mounted, then I'll start testing the Gecko and the motors.

    THEN, I'll start assembling the A4 itself.

    The long form of what I did today, with more pics, is up on my blog:
    MicroCarve A4 CNC Build Progress

    http://saundby.com/cnc --my website
    http://catsonkeyboards.blogspot.com/ --my blog


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    Nice! On the current limit divider what resistors would you use to make it 3 volts at 25ma?
    Thanks



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    Quote Originally Posted by jjacstcy View Post
    Nice! On the current limit divider what resistors would you use to make it 3 volts at 25ma?
    Thanks
    Starting with 48V, we'd need to divide that by 16 to get 3V.
    For 25mA, we'd want 48/.025=1920 ohms on the high side.
    1920/(16-1)=128 ohms on the low side.

    In real resistors I'd use a 1.8K ohm on the high side, 120 ohm on the low side. This'll give you 3V at 26.7mA.

    Check my numbers, or build one and measure it. I'm pretty bushed right now, but now you know the process to figure it out.

    Note that the current is what will flow through a dead short on the low end of the resistor divider. A properly installed LED will show some resistance, which will vary by the LED. If it's not bright enough, keep the 15:1 ratio between the high and low resistances and move to lower value resistors. E.g. you'll get up to 32mA with 1.5K and 100 ohm resistors with a dead short across the low end (shunting the 100 ohm resistor). A bit less current will flow with an LED in the circuit.

    My process is to figure out close values in my head, grab whatever is close to the top of the parts drawer for resistors in that range, hook them up to the bench supply with microjumpers, and see what I get with the multimeter, testing both voltage from ground to the union of the resistors, and current when placing the meter across the lower resistor in current measurement mode. Then I clip in a representative LED, if I'm smart. If I'm not, I make the divider cable, put it in, get disappointed because the LED isn't bright enough, then decide whether to replace the LED or the divider cable.

    Last edited by saundby; 04-05-2011 at 01:42 AM.
    http://saundby.com/cnc --my website
    http://catsonkeyboards.blogspot.com/ --my blog


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    Default Gecko G540 Power-Up!

    I got power to the Gecko today.

    I changed my mind on the fan setup I'd planned yesterday. I decided to have two fans on one side of the enclosure blowing in, two on the other side blowing out. I also checked the airflow on the various fans I have around and determined that the larger CPU-style fans blow a lot more than the smaller fans (something like 70mm vs 50mm, I haven't taken a rule to them.)

    So I cut two more fan ports into the case, put the mesh back over it all, installed the fans, wired them up and tested them. Then I put a connector on the fans and put a mating connector on the power supply.

    Finally, I fit the whole thing together, wrangling wires and doing some trimming to accommodate the fans.

    Then I led the power supply wires for the Gecko out of the hole cut in the back for the Gecko (I removed the Gecko after the test-fit, didn't want to take a chance of damaging it), hooked them up to the Gecko, plugged in and hit the power switch.

    It worked fine. I got power and fault lights on the Gecko (no E-Stop installed yet, just power.)

    Time to hit the sack now, tomorrow I'll mount up the Gecko, jumper the E-Stop until I've actually got a switch for it, and continue testing. Maybe even start assembly on the A4, but that's starting to look like Wednesday. *sigh*

    At some future point I'll have to open this enclosure back up and tear down a bit again to cut the holes for the E-stop switch connector and the limit switches connector in the back panel.

    Pics tomorrow.

    http://saundby.com/cnc --my website
    http://catsonkeyboards.blogspot.com/ --my blog


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    Thanks for the info!



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    Started wiring the motors today.

    I have some Belden 8424 OJ cable (4 conductor with shield, 20ga.) recovered from another project some years ago. It's been unused until now because of crud crusted on it. I washed it up, measured it, and cut the first length, prepped it & went through my resistors to select ones for the motor current resistors for the cables, & drew up a wiring diagram for myself so that I have a guide and know what I've done later.

    Then time ran short.

    Looking forward to spinning a motor, and more, tomorrow. Thu & Fri are when I have the most time, usually.

    http://saundby.com/cnc --my website
    http://catsonkeyboards.blogspot.com/ --my blog


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    I used the resistors you suggested and I have a perfect 3 volts. The resistors get a little warm is that normal? I am only using 1/8 watt, that's what I had on hand. Thanks for the help!



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    Quote Originally Posted by jjacstcy View Post
    I used the resistors you suggested and I have a perfect 3 volts. The resistors get a little warm is that normal? I am only using 1/8 watt, that's what I had on hand. Thanks for the help!
    1/8 watt should be enough, if you're getting 27mA at 3V, that's 0.081 watts, compared to 1/8 watt which is .125 watts. Still, you may want to measure your current at the high end and middle of the divider to see how close you are to the limit. For the current measurement at the top of the divider (between the 48V supply and the 1.8K resistor) multiply 48V times your measurement to get the watts there. At the middle, short it with the ammeter and then multiply that by your 3V to check the power at that point in the circuit.

    It's sort of belt-and-suspenders (or belt-and-bracers, if you prefer) to check at both points, but that's the kinda guy I am.

    http://saundby.com/cnc --my website
    http://catsonkeyboards.blogspot.com/ --my blog


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