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  1. #11
    12 and a bit quid for 10 metres of screened MiL spec, post paid.

    http://cgi.ebay.co.uk/Cable-Screened...mZ330339933966

    .
    John S -

  2. Quote Originally Posted by John S View Post
    12 and a bit quid for 10 metres of screened MiL spec, post paid.

    http://cgi.ebay.co.uk/Cable-Screened...mZ330339933966

    .
    Thats 4 cores of 7/0.2, equivalent to 24AWG/CSA0.23mm2... its good for 3.5A max in signal usage, but no more 0.6A for power transmission over any distance.

    My preference would be http://cgi.ebay.co.uk/FOUR-CORE-SCRE...mZ300306498039 which has twice the rating and is £9.50 for 15m (£15 inc P&P)

    If you want alternate lengths, try CSE cables they sell 7/0.2 4 core screened at 42p and 16/0.2 at 53p/m plus VAT & P&P which is £15 for 10m (16/0.2)
    Last edited by irving2008; 02-08-2009 at 05:43 PM.

  3. #13
    Yup definitely a better choice and there may be even better, I didn't spend a lot of time looking.
    John S -

  4. #14
    Interesting possibilites. I wouldn't put 4.2A through 7/0.2. Even 16/0.2 is pushing it. It all depends on what temperature rise you can tolerate in the wire. I'd prefer 32/0.2 and that is the problem - with price and availability. I spotted CSE and their prices are good, but they charge £7.50 minimum delivery. With the conversion costing hundreds of pounds, is this a "ha'peth of tar"? Maybe I'll try the unscreened wire and see what happens. I can always re-wire.

  5. #15
    Stick a meter on the cables and you'll find you are nowhere near 4.2 amps PER CABLE

    Drivers are rated per phase, not per wire.

    .
    John S -

  6. #16
    Quote Originally Posted by John S View Post
    Got to admit Roy can weigh people up well.....................

    .

    I asked for that, still laughed my arse of though...:clap:

  7. #17
    Interesting point John. I'm new to stepper motors, so don't understand this. The motor I've ordered is 2 phase, 2.73V, 4.2A, 3.2mH, wired Bipolar Parallel, Zapp SY60STH86-30. I haven't got the kit yet to measure. So does this mean I rate the cable at 2.1 A? This could be good.

  8. Quote Originally Posted by pequod View Post
    Interesting point John. I'm new to stepper motors, so don't understand this. The motor I've ordered is 2 phase, 2.73V, 4.2A, 3.2mH, wired Bipolar Parallel, Zapp SY60STH86-30. I haven't got the kit yet to measure. So does this mean I rate the cable at 2.1 A? This could be good.
    Each pair of wires is a phase... so a 4.2A phase on bipolar means 4.2A is being carried in 2 wires. In full step mode only 2 of the 4 wires at any one time is carrying 4.2A and not 100% of the time, but the maximum current in any one wire is 4.2A.

    16/0.2 is rated for 3A continuous 6A peak in conduit, at 4A you will lose about a volt across a 1.5m length.

  9. #19
    I can't run a test because believe it or not I only have one small CNC running and it's hard to get to the motors on this one.

    I can do later in the week but it is interesting to actually check just what power is pulled on a stepper system.

    Geckodrive state that 2/3 of the maximum amperage of the motors is required so if you have a 6 amp motor they recommend 4 amps of power.
    i know at one stage when we were doing the prototype X3 kits we worked out that we needed 4 x 2.5 amp = 10 amp divided by 2/3 so we arrived at a 7 amp power supply.

    Once built running all 4 axis absolutely flat out drew just under 5 amps ???

    So someone do me a favour and stick a test meter in circuit with one of the motor leads, most of the cheap multimeters will handle 10 amp, and tell us what the driver is set to and what it pulls on a rapid move and a low speed cutting move.

    .
    John S -

  10. #20
    Seems to me all of the above is relevant if you are building in the wiring, in which case you may as well use whatever cable will handle the load.

    If (like me) your build has the cables unpluggagble via XLR sockets then my preference is to overbuild it to buggery in terms of cable so that they are mechanically robust.

    Hence will be using 4-core SY cable, 0.5 mm^2 conductors, with OD of 7.3mm which is within the 8mm max for the XLR plugs:

    http://www.eland.co.uk/electrical-ca...ble-cable.html

    Screening is a bit of a bonus. Current capacity is 7A per wire so should be an adequate safety margin on that front too :-)

    Can't remember the cost but last time I got some from a local electrical wholesalers it was very reasonable. Anyway I figure my time is the most valuable part of any 'hobby' build so I'd rather just do it once and make it bombproof so as not to have to go back and fix it later... especially with fiddly stuff like cables, which in my experience tend to get a hard life anyway.

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