1 or 2 dedicated 120VAC circuits for my CNC?

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20 Nov 2022 20:21 - 20 Nov 2022 20:24 #257177 by Sray69
Great information!

Some of these components are new to me so I might need some help determining what parts/specs I need. I did my best to try to figure them out myself first.

Questions:

E-stop Circuit Diagram


I was researching the ECX series contact blocks. I wanted to see what DC voltage they support. I finally found the electrical specs and it says that they support 24V 1.5A & 110V .5A DC. Then I looked at the Mesa manual to see what the output of the VFIELD is. It says 8-32V BUT it also states "CAUTION: VFIELD Must be connected directly to the DC power source with no switches, circuit breakers or relay contacts in the circuit. A fuse is acceptable but in no case should VFIELD be switched ON through a mechanical contact."
  • My question is, is the E-stop button a mechanical contact? In the diagram it shows that it is connected/disconnected through the NC contact block. 
24V Fuse
  • Not sure what type of fuse I am looking for or need. Fast blow/slow blow/ceramic/current limiting/midget/etc?
  • Since the fuse goes on the output of the 24VDC 2.5A PSU, would 3A fuse suffice?
24VDC DTDP Coil Relay
  • Would this one work? The circuit it is on is only running 2.5A. This is rated at 6A. They did not have any other options.
24VDC Coil Contactor
  • I found IEC Magnetic Contactors and Definite Purpose Contactors on AD's site.
    Which type do I need?
  • If the PSU input amps are 8A, should I get a contactor rated slightly above that rating? Or does it matter if I go much higher?
  • Would this one work? If not, can you give me an example of what I am looking for?
24VDC Coil SSR
  • I assume based on your diagrams that this would be NO?
  • Would this one work?
    • AutomationDirect solid state relay, panel mount, finger-safe hockey puck, 3-32 VDC input voltage, SPST, N.O. TRIAC, 10A contact rating, 24-280 VAC load voltage, zero cross
      www.automationdirect.com/adc/shopping/ca...)/ad-ssr6t10-dc-280a >
      • Not sure if I need Zero Cross or Random Cross?
      • And I am not sure what N.O. TRIAC means?
If you find that any of the parts I listed are not correct, can you give me an example of what I am looking for?

​​​​​​​Also, it would be great if I could find DIN versions of these if possible.
Last edit: 20 Nov 2022 20:24 by Sray69.

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21 Nov 2022 17:44 #257240 by spumco
  • ESTOP & switch
    • the estop circuit does not control the 24vdc PSU.  Once the main disconnect is closed (ON), the 24vdc PSU is energized and thus the 24vdc terminal blocks.  The Mesa power and field power are immediately energized; there's nothing between the PSU and the Mesa V+ terminals other than an (optional) fuse.
    • Yes, the estop button contacts are mechanical contacts
    • The only current going through the estop contacts are:
      • Contact set 1 - contactor and relay coil grounds (a few mA)
      • Contact set 2 - Mesa VFIELD to Mesa input pin (a few mA)
  • Fuse rule of thumb
    • Fast blow for protecting electronics and sensitive stuff
    • Slow blow for protecting things with large inrush currents (drive main input bus, VFD's, power supplies, etc.)
    • A 3A fast-blow fuse would be fine for the 24vdc circuits
  • 24vdc DPDT relay
  • Contactor
    • There is no harm in going with higher-capacity contactors, except:
      • More money
      • Physically bigger
      • Coil usually draws more current (but still not much)
    • Definite-purpose contactors work, but they're 'cheaper' than the IEC versions.
      • I honestly don't know why definite-purpose contactors exist, but I think they're less expensive because the housing and contacts are simpler.  I believe they're intended for use in assemblies which are never opened  - note that the terminals aren't 'finger-safe'.
    • Decide now what the contactor is going to control:
      • Just the 60vdc PSU, or the router motor as well?
      • If just the PSU, then the one you linked is suitable
      • If the router motor as well, then the 25A version of the same contactor would be suitable.
      • No need for aux contacts
      • both the Fuji and Weg IEC mini contactors are DIN-rail mountable.
  • SSR
    • Might as well just use another mechanical relay - i.e. same as above.  They're rated for 15A @120vac, and you aren't turning the spindle on/off frequently.
  • In fact... if it were me doing this I'd use 3 of the exact same relay & socket combos so I could have common spares:
    • #1 - 'estop' relay
    • #2 - spindle on/off relay
    • #3 - 5v signal to drive enable relay
    • Yes, you don't need DPDT relays for #2 & #3, but having a common component for all three items is quite handy.  And it makes your control box visually satisfying.
  • Bonus - terminal blocks
    • Ebay has great deals on DIN-rail terminal blocks, but suggest you search for a single brand and stick with it.  The accessories are never compatible across brands (jumpers, end covers, etc.).
    • DIN-rail terminal block fuse holders are great - small, neat, hold 5x20 (or 6mm) fuses. Jumpering a row of them makes wiring really tidy.  Just read the fine print to see what the max current is for that series.  Example:
      • Automation Direct Konnect-It fuse holder - rated for 6.3A
      • Automation Direct Dinnector fuse holder - rated for 30A (!)
I use the heck out of the AD stuff...  see?  visually satisfying (ignore the non-LCNC motion control):

 
 
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21 Nov 2022 17:53 #257241 by Sray69
WOW! I need to go through this slowly so I can digest it, but it looks like you were very thorough and detailed in your answers. Exactly what I needed.

Thanks so much!

BTW, the cabinet looks very clean! I hope I can do the same.

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21 Nov 2022 20:39 #257256 by Sray69
Yeah I reread that part about the VField multiple times last night and realized that I misunderstood it. Thanks for the clarification.

I am liking AD as well but I find that they are out of stock on a lot of things and the estimated restock dates are way out (months). Also a lot of items you have to buy packs instead of single pieces which is not ideal at times.

Fuse/Holder
I am finding it difficult to find DIN Fuse Holders for 5x20 or 6x30 fuses. The only 5x20's I have found is the Automation Direct Konnect-It fuse holder but I have to purchase a pack of 10 for $23. Also there is a Chinese version on Amazon where I only have to buy a 5 pack for $10 which is more acceptable (since I only need one) but the reviews say they are cheaply made compared to the AD ones.

I see there are many DIN fuse holders available for the 10x38 Midget style fuses. Does the size/type of fuse really matters as long as it is a 3A Fast Blow fuse?
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Thanks again for the detailed info. I feel I am starting to learn and understand a lot of these components.

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21 Nov 2022 20:55 #257258 by Sray69
Hey any alternative options for this?

They are out of stock and will not be available until next year. I have seen some on Amazon/eBay but they are only rated 10A. This is fine for the E-stop circuit and the 5v signal to drive enable relay but not for the Router Receptacle. If I need to change one of these to a different type that is fine. 

 

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21 Nov 2022 23:14 #257270 by Sray69
I did find some of the sockets that are rated at 16A at Zoro. Not terrible prices but factoring in shipping and it gets a little up there.

I do have a question about the 2nd diagram where the router SSR/receptacle is powered by the contactor. I am trying to understand why I need the SSR (for the router). From what I have read contactors are similar to relays but used for higher inductive/resistive loads. Couldn't the contactor go directly to the receptacle? From what I can tell, correct me if I am misunderstanding it, if either the contactor or the SSR circuits are disrupted, the other is also disrupted.

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22 Nov 2022 04:45 - 22 Nov 2022 04:49 #257300 by spumco
I had no idea AD was out of stock on so much.  This supply chain thing is getting annoying.

RELAY
Here's a good alternate:

www.ebay.com/itm/185208469210

Omron makes good stuff, and the seller has 10 of them.

Or you could use the SSR for the router recepticle now that you've got the estop-controlled contactor supplying the 120vac.  The SSR isn't as dodgy when big-brother contactor is holding all the cards.

FUSE HOLDER
The type/size doesn't matter, but the midget fuses are signficantly more expensive than 5x20's.  Or you can just use DIN breakers.

Here's a phoenix contact version:
www.ebay.com/itm/273758186816

CONTACTOR/RELAY
Note: contactors are relays.  They're just big, heavy, rated for high amps, and have a big old spring inside to break the connection. They also make an oddly satisfying 'thunk' when they energize.

The contactor supplies the 120v to the relay, and the relay (SSR or mechanical) lets LCNC turn the router on/off.  The contactor is just there to break the 120vac to everything in case of an e-stop.

If you wired the router receptical directly to the contactor, you - the human - have to turn the router spindle on/off manually even during an estop event.

You could connect the router relay (SSR or mechanical) directly to the incoming 120vac line power, but then the estop circuit wouldn't shut it off.

I figured you wanted the best of both worlds: LCNC can turn the spindle on/off, and the estop circuit will kill both the drive power and the router motor even if LCNC is trying to spin it up (it shouldn't, but there I go again not trusting computers).  In addition, you - human - can always turn the router off by switching it off on the router itself.

And no... if you turn the SSR/relay on/off, it does nothing to the contactor.  Note that there are TWO 120vac 'hot' lines going through the contactor.  One goes to the 60vdc PSU, the other goes to the input side of the SSR/relay.

You're using the contactor contacts (ha!) like a couple of SPST relays tied together.  You could, in fact, use two single-pole contactors both tied to the same estop circuit, but 1 and 2-pole DIN-rail contactors are somewhat rare.
Last edit: 22 Nov 2022 04:49 by spumco. Reason: dumb mistake
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22 Nov 2022 04:52 #257301 by spumco
ARRGH Can't edit the last post

DISREGARD THIS PART:
If you wired the router receptical directly to the contactor, you - the human - have to turn the router spindle on/off manually even during an estop event.

That's late-night brain fade.  Of course the router recepticle would turn off if the contactor were de-energized.  Duh.

Carry on...
 
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23 Nov 2022 01:48 #257418 by Sray69

You could connect the router relay (SSR or mechanical) directly to the incoming 120vac line power, but then the estop circuit wouldn't shut it off.

But the E-stop button when pressed breaks the signal going to the digital input on the Mesa board. When this happens can't LCNC turn off the 24V output to the router relay, killing power to the receptacle as well? And then the opposite once the E-stop circuit is reset? Much like the driver enable SSR.

I think I get the rest of what you said. Thanks for all the explanations. Big help!I have been putting together my parts list to run my 30A circuit and it dawned on me that I was told to use GFCI's for the outlets the CNC are plugged into. Now that I am running a 30A line, I do not see any 30A 120V GFCI receptacles. What do others do in this situation?
 It looks like the Omron relay (LY2N-D2) you linked to is only 10A. The socket that it is plugged into is rated up to 15A. This would work for my DC to DC circuits but I feel that I need at least a 15A for the DC to AC circuit (router).I found the spec sheet for the Omron LY series relays. I was able to determine that LY2's are DPDT and the LY1's are SPDT. But when I went to figure out the ratings it gets a little confusing.  The chart below shows resistive and inductive ratings under the Rated Load for both. BUT then they show a Carry Current and a Max Operating Current that is the same rating for both resistive and inductive. Do I go off the Rated Load? If so, then none of the Omron's will work for my router circuit.
 

Anyway I went ahead and ordered 2 of the LY2N-D2's with the 15A sockets for the DC to DC circuit. I then ordered one of the AutomationDirect 15A relays you mentioned for the DC to AC router relay, and will use the extra base. That will give me a spare LY2N-D2 for the DC to DC circuit.

I think I am close to ordering the rest of the components. Thanks
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23 Nov 2022 06:02 #257427 by spumco
But the E-stop button when pressed breaks the signal going to the digital input on the Mesa board. When this happens can't LCNC turn off the 24V output to the router relay, killing power to the receptacle as well? And then the opposite once the E-stop circuit is reset? Much like the driver enable SSR.

Correct... and this is where we get in to opinions & preferences.  If the router relay is fed from direct line voltage and not through the contactor, if LCNC throws up (or the SSR fails closed) the router won't turn off.

Remember earlier when I said 'belt and suspenders'? My opinion is that a human should be able to turn off all motion and meat-cutting equipment without relying exclusively on software or software-controlled hardware.  LCNC is stable, and there are plenty of peoply who rely on software (LCNC or otherwise) for safety stuff.  I dont, and that's why I've suggested the scheme presented.

For a dedicated recepticle I wouldn't use a GFCI.  They trip when you least want it.

Sorry about the Omron... I zoomed in on the photo in the listing and I guess I misread it, or saw the base rating and confused it with the relay.

The router should be classified as an inductive load, which means they're rated for 7.5A in the DPDT config.  That's technically OK for the router (according to the router specs), but I suspect the contacts won't last a long time.

I've got one of the AD 782 DPDT relays switching a 12A vacuum on a router table, and another one switching a 10A(ish) coolant pump and they're doing fine after a couple of years of steady service.

Next step is playing tetris with all the components in the enclosure.  Leave yourself plenty of room if you can, otherwise you'll be using foreceps to get the wires in the component terminals.
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