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Thread: DIY - Choosing MCBs and magnetic contactors, etc. - need advice

  1. #21

    Default Re: DIY - Choosing MCBs and magnetic contactors, etc. - need advice

    Quote Originally Posted by Jim Dawson View Post
    A relay or contactor can be thought of as a remote controlled switch. You energize the coil and this electromagnetically closes the contacts, thus you can control multiple contacts with a single switch. The Aux contacts are normally used as a ''seal-in'' or self holding contact to keep the coil energized in the case of a momentary switch. There are other uses also. In your case, the seal-in would be accomplished by an external source, the E-stop/control power relay.

    Below is an example of the wiring using aux contacts for seal-in along with a momentary switch. But the power is supplied through the ESR1 relay, so if the E-stop button is pushed, the power is dropped to the contactors. This is the control circuit for the panel I posted above.

    NOTE: A relay and a contactor are electrically identical, but a relay becomes a contactor when used to switch high current loads like motors and drives, rather than control power loads like other relays and contactors. On drawings these are usually noted as CR = control relay, and C = contactor.
    Hi Jim,

    Being the novice that I am and not having had much exposure to electrical diagrams, I'm not entirely sure what is going on at the place I've circled in red in your drawing. Is that a power off button? If so is it a momentary contact switch? I believe you indicated that the power on button is a momentary contact switch? The drawing does or does not show the 240 load voltage? What are the parallel lines labeled ESRI 1 and 3 and 8 and 6? Is the ESR 2 and 7 a separate relay? Can you tell I'm a bit confused?

    So I'm working under the assumption that for my 4 servo drives I need 1 10 Amp breaker for each, 1 12 Amp Contactor that needs 2 auxiliary contacts 1 NO and 1 NC for each drive. I can use 1 momentary contact power on switch for all 4 contactors with a power on indicator light. The power off switch I'm unsure about whether it is a momentary contact switch and possibly hooks to the available NO auxiliary contact, and the E-stop will be wired to the NC auxiliary contact.

    Do you have any recommendations for switches and power indicator lights?

    DIY - Choosing MCBs and magnetic contactors, etc. - need advice-e-stop-servo-contactors-jpg

    Attached Thumbnails Attached Thumbnails DIY - Choosing MCBs and magnetic contactors, etc. - need advice-e-stop-servo-contactors-jpg  


  2. #22
    Community Moderator Jim Dawson's Avatar
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    Default Re: DIY - Choosing MCBs and magnetic contactors, etc. - need advice

    Sorry, I should have labeled things for you. This drawing does not show the 240V power connections, this is only the 24VDC control power. Please understand that the drawing above is not for a CNC machine, and everything is manually controlled. But it is a simple circuit showing the basics.

    the ----| |---- is a Normally Open (NO) contactor or relay contact. The numbers are the relay terminal, or switch contact numbers. A Normally Closed (NC) contact would be ----|/|-----

    The 2 and 7 are the terminal numbers for the relay coil. Depending on the relay these could be labeled A1 and A2, depending if it is an IEC (European standard) or American standard relay.

    The switch contacts you circled are NO contacts for the E-stop push button, all that it does is turn on the red light in the push button to notify that operator that the E-stop button is pushed in. Saves confusion when the machine won't run. The E-stop button is a maintained contact, with twist to release. The top contact set is NC, and the bottom contact set (circled) is NO.

    The Power On button is momentary contact, and would normally be labeled as such (MOM), but I'm lazy.

    In your application the contactors may not require any auxiliary contacts, or you may use the NO contacts as a seal-in as I did above. There are few different way of setting thing up.

    I like to power the drives up one at a time to limit the in-rush current. I do this under computer control with a 1 second delay between each drive, you may want to do it differently. I also require an output from the computer (controller) that is in the E-stop circuit to prevent powering up the drives until computer is happy. This also allows the computer to trigger an E-stop on a fault condition, but under no condition would you allow the computer to energize the control power. This must be done by the operator with a push button.

    I buy almost exclusively from Automation Direct. https://www.automationdirect.com/adc...20desc&start=0

    I'm sure more questions will come up, I or someone else will try to help you through this.

    Jim Dawson
    Sandy, Oregon, USA


  3. #23
    Community Moderator Al_The_Man's Avatar
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    Default Re: DIY - Choosing MCBs and magnetic contactors, etc. - need advice

    As Jim said, 24dc control power is the preferred choice now, and has been the practice for some years now.
    The advantages is safety, LV for LED indicators, as well as contactor. relays etc, for which the efficiency and reliability is much higher for DC coils and solenoids etc.

    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.


  4. #24

    Default Re: DIY - Choosing MCBs and magnetic contactors, etc. - need advice

    Quote Originally Posted by Jim Dawson View Post
    Sorry, I should have labeled things for you. This drawing does not show the 240V power connections, this is only the 24VDC control power. Please understand that the drawing above is not for a CNC machine, and everything is manually controlled. But it is a simple circuit showing the basics.

    the ----| |---- is a Normally Open (NO) contactor or relay contact. The numbers are the relay terminal, or switch contact numbers. A Normally Closed (NC) contact would be ----|/|-----

    The 2 and 7 are the terminal numbers for the relay coil. Depending on the relay these could be labeled A1 and A2, depending if it is an IEC (European standard) or American standard relay.

    The switch contacts you circled are NO contacts for the E-stop push button, all that it does is turn on the red light in the push button to notify that operator that the E-stop button is pushed in. Saves confusion when the machine won't run. The E-stop button is a maintained contact, with twist to release. The top contact set is NC, and the bottom contact set (circled) is NO.

    The Power On button is momentary contact, and would normally be labeled as such (MOM), but I'm lazy.

    In your application the contactors may not require any auxiliary contacts, or you may use the NO contacts as a seal-in as I did above. There are few different way of setting thing up.

    I like to power the drives up one at a time to limit the in-rush current. I do this under computer control with a 1 second delay between each drive, you may want to do it differently. I also require an output from the computer (controller) that is in the E-stop circuit to prevent powering up the drives until computer is happy. This also allows the computer to trigger an E-stop on a fault condition, but under no condition would you allow the computer to energize the control power. This must be done by the operator with a push button.

    I buy almost exclusively from Automation Direct. https://www.automationdirect.com/adc...20desc&start=0

    I'm sure more questions will come up, I or someone else will try to help you through this.
    Thanks for the Info Jim. I'm trying to picture the Contactor integration with the E-Stop AND a power off button to de-energize the Drive power. Would that necessitate a relay between the E-Sop Button/Controller and The contactor? Essentially the power off button would be for cutting power to the drives before shutting down the controller box, but that's just how I imagine things should work. If that should only happen with an E-Stop button then please let me know and I'll adjust my thinking.

    With all the breakers and Contactors and other electrical parts, building this control box is going to be at least 4 times more expensive than I originally estimated.

    --Tom

    Last edited by TeeTomTerrific; 05-12-2022 at 09:48 AM.


  5. #25

    Default Re: DIY - Choosing MCBs and magnetic contactors, etc. - need advice

    Quote Originally Posted by boydage View Post
    All good stuff. I guess I was just saying, a control transformer is all that would be needed to then increase the availability and lower the cost of the build. Personally for me, Diy is about using what we can. Spend as little as possible. Use hours and hours of our time up making something ourselves instead of buying it for $100. That kind of stuff.



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    Hi boydage,

    I think there are two distinct approaches for DIY. the first one is the one you mentioned where the person is limited by funds so using what you can spending as littlie as possible and making do with what you can afford, beg or borrow to achieve a functional machine. The second approach is driven primarily by the desire to build the best engineered machine you can at the lowest cost so that the result is something better than you could buy outright for half the price or less. This is essentially my approach. Buying a quality part designed for purpose may be more expensive than adapting another part, but the end result will likely be better engineered to be safer and and or last longer or function more efficiently, etc. This second approach still involves the sweat equity portion of the first approach, but with a better budget. In both approaches though the fun part is that it's DIY where you can learn and expand your knowledge and skills doing something you have never done before.

    --Tom



  6. #26

    Default Re: DIY - Choosing MCBs and magnetic contactors, etc. - need advice

    Quote Originally Posted by Al_The_Man View Post
    As Jim said, 24dc control power is the preferred choice now, and has been the practice for some years now.
    The advantages is safety, LV for LED indicators, as well as contactor. relays etc, for which the efficiency and reliability is much higher for DC coils and solenoids etc.
    Hi Al,

    I totally buy into that position on 24VDC. I'm just very much a novice when it comes to electrical engineering. I know that I don't know what I don't know so I'm relying on the guidance of kind folks like you and Jim to help guide me and answer my questions so that I end up with a well designed and well built Controller box for my DIY CNC machine project..

    Thanks!

    --Tom



  7. #27
    Community Moderator Jim Dawson's Avatar
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    Default Re: DIY - Choosing MCBs and magnetic contactors, etc. - need advice

    Quote Originally Posted by TeeTomTerrific View Post
    Thanks for the Info Jim. I'm trying to picture the Contactor integration with the E-Stop AND a power off button to de-energize the Drive power. Would that necessitate a relay between the E-Sop Button/Controller and The contactor? Essentially the power off button would be for cutting power to the drives before shutting down the controller box, but that's just how I imagine things should work. If that should only happen with an E-Stop button then please let me know and I'll adjust my thinking.

    With all the breakers and Contactors and other electrical parts, building this control box is going to be at least 4 times more expensive than I originally estimated.

    --Tom

    You really don't need both an E-stop button and a power off button. Just the E-stop button will be fine. But you do need a momentary contact power on button. You can call this button ''Control Power'' or ''Servo Enable''. The E-stop and Control Power buttons would control a relay that would then supply power to the contactor coils. I normally call this relay ''E-stop relay'' or ''Control Power relay''. Now between the control power relay and the drive contactors you could have additional electrical logic to control individual contactors, or you could energize all of them at the same time. However, I don't like energizing multiple high in-rush devices like servo drives all at the same time. It throws a momentary but very large load on the main power, fortunately this is mitigated by the resistance of the wire feeding the panel in most home shop installations. In heavy industrial applications where very high energy main power feed is available, the in-rush needs to be managed at the machine panel level.

    In your case since you are using single phase, rather than normal contactors the cost can be reduced by using PRD style power relays. https://www.amazon.com/TE-CONNECTIVI...6&sr=8-20&th=1

    Here is a picture of my lathe servo drive panel, this one is 3 phase. There is a lot more hardware in my lathe that is not shown in this picture, this is just the axis drive sub-panel.

    Starting at the top, there is the power distribution block, feeding 4 breakers. The 4 breakers feed the 4 drive contactors. To the left of the breakers are 4 ice cube relays, these are the E-stop/control power relays. In this case I have both an E-stop and a separate control power circuit, and am switching both 24VDC and 120VAC circuits, thus the need for 4 relays. In your system only one E-stop/control power relay would be needed. To the left of the contactors are the 1 amp fuses for the low power control circuit for the drives.

    DIY - Choosing MCBs and magnetic contactors, etc. - need advice-img_1958-jpg

    Here is about the minimum that I would concider:

    Power

    DIY - Choosing MCBs and magnetic contactors, etc. - need advice-cnc-power-jpg

    Control

    DIY - Choosing MCBs and magnetic contactors, etc. - need advice-cnc-control-jpg

    Attached Thumbnails Attached Thumbnails DIY - Choosing MCBs and magnetic contactors, etc. - need advice-img_1958-jpg   DIY - Choosing MCBs and magnetic contactors, etc. - need advice-cnc-power-jpg   DIY - Choosing MCBs and magnetic contactors, etc. - need advice-cnc-control-jpg  
    Last edited by Jim Dawson; 05-12-2022 at 02:14 PM.
    Jim Dawson
    Sandy, Oregon, USA


  8. #28
    Member mactec54's Avatar
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    Default Re: DIY - Choosing MCBs and magnetic contactors, etc. - need advice

    Quote Originally Posted by boydage View Post
    Any reason why you guys are determined to use 24v control power? You are already using higher voltages for other portions of your circuits. So safety is moot unless you do a poor job.

    Not dishing on anyone or chest puffing. Just my own experience I used 110 sometimes 230. Lots of cheaper contactors avaiable because its the common industry standard. Well here anyways. No need to use the fake ebay ones ive seen some of them. Spares in stock at the shop down the road. Easy and done.

    My two cents. Is proper earth earth earth.

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    24v is industry standard for all control circuits

    Mactec54


  9. #29
    Community Moderator Al_The_Man's Avatar
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    Default Re: DIY - Choosing MCBs and magnetic contactors, etc. - need advice

    Quote Originally Posted by mactec54 View Post
    24v is industry standard for all control circuits
    And that is 24V DC !

    Edit:
    Missed the 4!

    Last edited by Al_The_Man; 05-13-2022 at 10:36 AM.
    CNC, Mechatronics Integration and Custom Machine Design

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    Albert E.


  10. #30
    Member mactec54's Avatar
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    Default Re: DIY - Choosing MCBs and magnetic contactors, etc. - need advice

    Quote Originally Posted by Al_The_Man View Post
    And that is 2V DC !
    24V DC I hope 2V DC would be a struggle

    Mactec54


  11. #31
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    Default Re: DIY - Choosing MCBs and magnetic contactors, etc. - need advice

    Nice one Tom. Make sure you post some pics of your progress. B

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DIY - Choosing MCBs and magnetic contactors, etc. - need advice

DIY - Choosing MCBs and magnetic contactors, etc. - need advice