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Thread: r4z0r7o3's Crucible-furnace lifting mechanism / transport-stand.

  1. #331
    Senior Member r4z0r7o3's Avatar
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    Jul 2015
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    Raleigh, North Carolina
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    Extra! Super! Duper! Exciting work!

    Drilled a 1-1/8" hole in the back of the control box. Then I used an online calculator (somewhere) to calculate the angles and distance needed for that 1" offset EMT conduit bend. (20* and 2-in. IIRC).


    Printed out an updated schematic (minor changes/additions):


    Printed out an updated wire number / terminal position key (a.k.a. Screw who where):
    Code:
    Main Enclosure
    ==============
    --------------
    
    110v Mains #0001 -> Sw1 -> #0003 10A Fuse -> PSU
    0v Neutral -> PSU
    GND -> Chassis -> Ain3 (below)
    
    Motor Black -> #0008 && #0011
    Motor White -> #0009 && #0010
    Motor GND   -> Chassis
    
    
    Control/Terminal Box
    =====================
    ---------------------
    
    Wire #  A IN                         Wire #  A OUT
    ======= ==============               ======  ==============
    #0006   1 63v+ PSU (out 1)                   1 E/D SW2+ (inp)
    #0004   2 12v+ PSU (out 1)                   2 N/C
            3 Chassis Ground (lug)               3 Chassis Ground (Y out)
    #0005   4 12v- PSU (out 1)                   4 Dout3 (Y inp)
    #0007   5 63v- PSU (out 1)                   5 E/D SW2- (inp) && Dout3 (Y inp)
    
    
            B IN                                 B OUT
            ==============                       ==============
    #0013   1 U/limit SW4- (out)         #0009   1 Motor - (Y inp)
    #0015   2 D/limit SW5- (out)         #0011   2 Motor + (Y inp)
            3 E/D SW2+ (out)                     3 Snub D1+ (inp)
            4 E/D SW2- (Y out)                   4 Snub D2+ (inp)
            5 E/D SW2- (Y out)                   5 U/O/D SW3- (inp)
    
    
            C IN                                 C OUT
            ==============                       ==============
            1 Snub D1- (out)                     1 U/O/D SW3+ (Y inp)
    #0012   2 U/limit SW4+ (out)         #0008   2 Motor + (Y inp)
            3 Chassis Ground (Y inp)             3 N/C
    #0014   4 D/limit SW5+ (out)         #0010   4 Motor - (Y inp)
            5 Snub D2- (out)                     5 U/O/D SW3+ (Y inp)
    
    
            D IN                                 D OUT
            ==============                       ==============
            1 U/O/D SW3 UP+ (out)        #0018   1 U/limit SW4+ (inp)
            2 U/O/D SW3 DN- (out)        #0017   2 D/limit SW5- (inp)
            3 Chassis Ground (Y inp)             3 Aout4 && Aout5 (Y out)
            4 U/O/D SW3 UP- (out)        #0019   4 U/limit SW4- (inp)
            5 U/O/D SW3 DN+ (out)        #0016   5 D/limit SW5+ (inp)
    Connected all the wires to the "input" (left) side of each terminal...


    ...and then to the "output" (right) side. Applied the clear plastic protective covers on each.


    Then the real fun began, continuity testing and measuring certain connections...


    ...comparing to expectations based on measuring the PSU outputs and Motor coil resistances. Also checked all the switches were actually switching. Here's the list:

    Code:
    All switches open
    (limit switches normally-closed)
    ================================
    --------------------------------
    
    A1 -> A5:          About 6.5kΩ
    A1 -> B3:          N/C
    A2 -> A4:          About 5kΩ
    A1 & 5 -> B1 & 2:  N/C
    A1 & 5 -> C2 & 4:  N/C
    B3 -> C1 & 5:      700kΩ
    C2 -> C4:          About 1.5Ω
    D1 -> D5:          About 1.5Ω
    D2 -> D4:          About 1.5Ω
    
    All switches On & Up
    ====================
    --------------------
    
    A1 -> D2:          About 6kΩ
    A1 -> D5:          About 6kΩ
    A1 -> D4 any limit:  N/C
    
    All switches On & Down
    ======================
    ----------------------
    
    A1 -> D4           About 6kΩ
    A1 -> D1           About 6kΩ
    A1 -> D2 any limit:  N/C
    Actually found a few problems (swapped wires) to fix, and a few unexpected things (that turned out to be normal e.g. reverse leakage through snubber diodes).

    Note: The floating terminal blocks are only temporary. I needed to see where I could comfortably mount them w/ the wires attached, b/c they're not all a uniform length.

    Finally, I wheeled it outside, into the middle of a big field. Plugged it in...
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    ..turned it on...
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    ...flipped the "up" switch...
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    ...and...
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    Kidding...actually I'm too scared (and hungry) to do it now, soon though
    "Things that are complex are not useful, things that are useful are simple."
    - Mikhail Kalashnikov

  2. #332
    Senior Member
    Join Date
    Nov 2012
    Location
    Ontario, Canada
    Posts
    2,096
    I've been cobbling electrical systems for bordering on decades. Everytime i turn anything on that I made, I cringe just a little bit...lol.

    The death of fear spawns complacency.... <--write that down.
    FLAME ON...!!!!

  3. #333
    Senior Member r4z0r7o3's Avatar
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    Jul 2015
    Location
    Raleigh, North Carolina
    Posts
    1,066
    Quote Originally Posted by J. Vibert View Post
    The death of fear spawns complacency
    Ha, U sure you don't mean "Fear of death"

    So I figured the PSU is protected by a slow-blow fuse, but there's nothing protecting the motor really.

    So I just ordered 20x (each) of three different sizes of PTCs (resettable/thermal fuses). I can gang ones of the same rating, in parallel, to (more-or-less) dial in the amperage I want them to cut out at. These will protect the motor from excessive current and heat, over a given amount of time.

    For example, the biggest one I ordered is rated for 650ma of holding current, and 1.3a cut-out (60v rated). If I put 4 in parallel, that means they'll allow up to (0.65 * 4) 2.6 amps through (basically forever). However, anything above that and they'll start getting hot. The closer the current gets to 5.2 amps (1.3 * 4) the faster they heat up (nearly instant at full load). The hotter they are, the more resistant they become to current. Let them cool down, and they work normally again.

    Bottom line is, if something mechanical goes wrong, like the limit switches failing, or my head gets stuck in the rails. That will cause the motor to draw more current, especially if it's at a dead-stall. The PTCs heat up, and limit the current to the motor (or stop it outright). Remove/fix the problem, let the PTCs cool off, and it's good to go again. So they're a cheap (like $0.25 ea.) way to control both the duty-cycle and protect the contraption from harming the motor, w/o having to run out and find a replacement fuse.




    While I wait for delivery, my plan is to double-check my wiring with a small battery-pack and some LEDs (I have lots). I'll just disconnect the PSU (I already know it works), and connect up the battery leads. Then I can test it out easily w/o fear of leaving shit-stains anywhere, or explodicating anything expensive
    "Things that are complex are not useful, things that are useful are simple."
    - Mikhail Kalashnikov

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