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  1. #11
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 6 Hours Ago Has been a member for 8-9 years. Has a total post count of 1,452. Received thanks 146 times, giving thanks to others 5 times.
    There's nothing wrong with using a relay to switch mains voltage, provided it's rated for the voltage and current.
    However going by the latest wiring diagram, you'll struggle to get a relay capable of the required current with 5 contacts. The VFD will draw 8 amps at full power, and along with the stepper PSUs, there will also be a surge during power up.
    You could use a 3PDT relay, such as RS part number 536-912 which is rated at 10A and power the VFD and PSUs via one contact, however I'd personally use something like 488-2610 with one for the VFD, one for the PSUs, and one for the E-stop circuit.

    Note, both those part numbers are for relays with 24VDC coils, but will give you an idea of the type of relays, as they're both a pretty common style/size of relay.
    Avoiding the rubbish customer service from AluminiumWarehouse since July '13.

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  3. Last edited by Gary; 04-08-2016 at 07:13 AM.

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  5. #13
    Thank you both for your informations, I will be checking that lot out and ordering as required.

    I also found a link to this guide;

    http://ecatalog.squared.com/pubs/Mac...0140CT9201.pdf

    So will be checking this out, the table 3 shows something I believe.

    Many thanks,
    Ian
    Life is best lived @ G0......

  6. #14
    Quote Originally Posted by m_c View Post
    You could use a 3PDT relay, such as RS part number 536-912 which is rated at 10A and power the VFD and PSUs via one contact, however I'd personally use something like 488-2610 with one for the VFD, one for the PSUs, and one for the E-stop circuit.

    Note, both those part numbers are for relays with 24VDC coils, but will give you an idea of the type of relays, as they're both a pretty common style/size of relay.
    HI m_c,

    Is it possible to use a boost converter to input 12VDC up to 24VDC to power the RS items or do I need a dedicated 24VDC PSU?

    Just trying to work through what is best to do?

    Many thanks,
    Ian
    Last edited by nairepooc; 04-08-2016 at 10:52 AM.
    Life is best lived @ G0......

  7. #15
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 6 Hours Ago Has been a member for 8-9 years. Has a total post count of 1,452. Received thanks 146 times, giving thanks to others 5 times.
    You could use a booster, however 12VDC versions of those relays should be available.
    I only gave the 24VDC part numbers, as those are what I use, and had the numbers handy.

    12V version of 3PDT is 536-900, and DPDT is 488-2604

    What is best to do depends on the machine, and how you implement safety features.
    Going by the components you have listed, I'm going to guess this is a reasonably sized router?
    Personally, I wouldn't worry too much about limit switches, as provided the design is good, should you run into a hard limit, the motor will stall and simply sit stay stalled. With dual Y axis, I'd be more concerned about racking, but no limit switch is going to prevent that.
    If I was to fit limit switches, I'd hard wire them into the E-stop circuit, as you want things to stop as quickly as possible should you hit one, but then that means you can't use the limit switches for homing.

    In a commercial setting, safety relays are good, however for smaller home machines I personally think they are overkill. The major benefit of them is they monitor the contacts, so should a set of contacts stick/weld shut, they'll prevent the machine from starting. If you were to use standard relays, should contacts stick shut, you would be none the wiser unless you noticed power was still on when it shouldn't be.
    There are also time delayed safety relays, which purpose is to maintain power to certain circuits for a short period. A good application of them is servo controlled machines, where when the E-stop is triggered, it subsequently triggers the servo drives to carry out a fast stop, before then killing power to the drives after a few seconds. This allows the machine to be stop safely under power, before all power is removed, as otherwise the servos risk freewheeling to a stop without power.

    As for contactors. They are essentially just a big relay, however they're contact design means they're less likely to fail/weld shut. Whereas a typical relay has a single contact that opens/closes, a contactor works by bridging two contacts with a bar/plate. Should a contactor weld shut, it's unlikely both ends of the bar will weld, so when it releases the opposite end should still break the circuit. Off course, unless you have monitored contactors, you'd be none the wiser unless the contactor failed completely.

    The big thing though, is regardless of relays or contactors, is provided they're sized/rated/fused correctly, you should not have any problems with contacts welding or burning out.
    My concern would be inrush currents as things initially get powered up. Even though the VFD/Spindle maybe only needs 8A under full load, it could have a power on surge of 20A as the internal capacitors charge up. The same for the switch mode power supplies. Any good technical data/specification sheet will state surge currents.
    Avoiding the rubbish customer service from AluminiumWarehouse since July '13.

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  9. #16
    Wow m_c,

    Super lot of information there. I had just found the 488-2604 myself ;-)
    Seems I have a lot to learn.

    Yes the machine is 800mm X axis, 1000mm Y axis and 300mm Z axis.

    Like you say next thing is limits or homing!

    Once agian many thanks
    Life is best lived @ G0......

  10. #17
    Updated wiring with fuses and RS part numbers, etc.
    Hope this is workable?
    Click image for larger version. 

Name:	HERBERT WIRING - Schematic 02.jpg 
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    Life is best lived @ G0......

  11. #18
    One of the things I thought about was how best to fuse the 2 drivers which drive each side of the gantry.

    I originally had one per driver, but in the end went for double the current rating and fed them both from the same fuse. If the fuse blew, it would stop the gantry.

    With one fuse per side it would twist. I posted for opinions at the time but got nothing back.
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

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  13. #19
    Quote Originally Posted by routercnc View Post
    One of the things I thought about was how best to fuse the 2 drivers which drive each side of the gantry.

    I originally had one per driver, but in the end went for double the current rating and fed them both from the same fuse. If the fuse blew, it would stop the gantry.

    With one fuse per side it would twist. I posted for opinions at the time but got nothing back.

    That is a great idea and not one that immediatly springs to mind.
    I will incorporate that into the design.

    Many thanks,
    Ian
    Life is best lived @ G0......

  14. #20
    I now have all my bits around me and startng to work through the wiring schematic;
    Parts are;
    2 off 36V - 400W PSU (for drivers)
    1 off 24V - 60W 2.5A mini rail mount PSU
    1 off 5V - 10W 2A mini rail mount PSU
    1 off CP0-10V BOB (cnc4you)
    4 off CW5045 (cnc4you)
    1 off UC300 (cnc4you)
    2 off E-Stops (2 pos NC)
    4 off 24V 10A DPDT rail mount relays
    1 off 4A type D MCB rail mount
    1 off 10A type D MCB rail mount
    1 off Rotary panel disconnect
    1 off 10A EMI filter (cnc4you)
    1 off Green reset (NO) panel push button
    2 off 24V fans (blown air into cabinet)
    1 off Green panel mount led (5Vdc - live)
    1 off Yellow panel mount led (24Vdc - live)
    2 off White panel mount leds (36Vdc - live)
    1 off VFD - HY02D223B
    1 off 2.2 water cooled spindle

    DIN rail mounting and red, black, yellow and fused connectors.

    Oh and I have been given a PILZ PNOZ 16S safety unit, just not too sure how to incorporate this.

    Any help would be most welcome guys
    Life is best lived @ G0......

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