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29th Jul 2021, 10:46 AM #1Diamond Member
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Source for 3phase machine switch box?
Does anyone know of good contactor based machine power switches?
I'm thinking of a little box with a big emergency stop button on the front,
and a power latched relay inside for safety after power outages et c.
Searches for 3 phase starter box show plenty of the traditional type
(small red and green buttons on a huge case),
but I haven't found anything I would like to put on a table saw, for example.
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29th Jul 2021, 11:21 AM #2Member: Blue and white apron brigade
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Do you need the contactor switch as well?
If so, you wont need a power latched relay inside for safety after power outages etc as most contactors already have this built in.
Unless you can find second hand then be prepared to shell out $$$ for a decent one.
In some cases it's getting like you might as well buy a VFD for similar money and get all the extra benefits.
If you want a big red off switch you can wire that into a the VFD low V control circuit.
An extra big switch can be obtained if a Large Paddle type switch is used.
Plenty of samples on ebay.
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29th Jul 2021, 07:16 PM #3Diamond Member
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Good point Bob - the Contactor IS the "power latched relay."
I have seen those paddle type things, but they look too flimsy to me. Something like this:
https://www.cef.co.uk/catalogue/prod...ion-metal-clad
looks a bit better (but that is just single phase? 2 switches)
For my Hercus lathe, I built a metal box with a metal emergency switch:
IMG_0007.jpg
Can always make something similar, but was hoping to not re-invent the wheel if something good already existed
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29th Jul 2021, 07:24 PM #4Member: Blue and white apron brigade
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29th Jul 2021, 08:02 PM #5Senior Member
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Thats simply a estop actuator with 3 contact blocks. A electromagnetic switch is designed so if power is supplied it requires a physical action to operate the switch and switch power. The estop you show , if released ( assuming NC contacts) the the power will be switched on. Only option is a small 3 phase starter. Can be wired with a remote stop start station with a mushroom head stop if needed so contactor box isnt in way of anything.
Diagram shows 24vdc power supply but easier option is 24vac power supply for retic controller and fit 24vac coil to contactor. That way parts are easy to get.
Full-voltage-non-reversing-3-phase-motors.jpg
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30th Jul 2021, 12:29 AM #6Diamond Member
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Indeed. Picture was illustrating a solid metal box, and a switch which will last when I bash it with my fist or a hammer
(unlike most small power switches I have seen).
More complicated motor control boxes (e.g. anything with a motor reverse, or a coolant pump) do seem to use 24V control, but that means an extra transformer or power supply in the box. Which means my simple little box now has 4 things in it; contactor, tranny, start button, stop button (and maybe a DIN rail to hold the contactor, and a terminal block).
P.S. for a small machine like that lathe, I don't mind if it accidentally turns on when someone plugs the 3phase plug in, but for a 12" circular saw blade, I wanted a bit more safety.
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30th Jul 2021, 12:21 PM #7Senior Member
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Buy a 3 phase magnetic motor starter with a 240vac coil. Dont worry about the buttons on the front of it except for the red which will work as the overload reset . then buy a stop start station to mount on front of machine. Wire up as per this diagram. Easy enough but should really get a sparky to do it , depends on state regs. You could also just buy the contactor and overload and fit into a small enclosure which may be cheaper, with the motor starter you will need to remove some of existing connections.
stop start.jpg stop start with neutral.jpg
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30th Jul 2021, 03:26 PM #8Senior Member
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I’ve never seen a hammer proof emergency stop switch, not saying they’re not made, but I’ve never seen one.
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30th Jul 2021, 03:41 PM #9Senior Member
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Thats why I used to install large Estop buttons like this one. At least they only hit it once.
e-stop.jpg
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2nd Aug 2021, 07:40 PM #10Senior Member
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Nigel
What's in your switch box at the moment, I believe your lathe is Hercus (9 inch or 260) & running on 3ph. Any chance of a picture of the inside. If you want a larger eStop, you should only have too put the new switch in series with the existing STOP button, as this interrupts the hold cct on the contactor.
Do you have a wiring diagram for it? I have copies of the original Hercus ones
JohnQLast edited by JohnQ; 2nd Aug 2021 at 07:42 PM. Reason: spelling
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2nd Aug 2021, 10:34 PM #11Diamond Member
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Hi John.
Hercus: Yes, 3 phase. Switch box is just a simple on/off, but I'm using a triple gang emergency stop switch instead of the usual seperate on/off:
IMG_0008.jpg
Table saw (Tanner): No switch box. Motor is just attached to a plug, just like these other old ones a Google image search found for me:
259815636.jpgblog4930119a100f96c51f1ff518c5bcea54.jpg
The Hercus can stay as it is - a simple "unsafe" power switch suits a simple machine -
unless I foolishly add extra functionality/circuitry (RPM meter, electronic lead screw?).
The table saw is the issue. For now I will just put a clipsal 56 series switch on it,
until I find a good little contactor based box?
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3rd Aug 2021, 03:43 PM #12Senior Member
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Nigel
Sorry, should have read all of the last line
"but I haven't found anything I would like to put on a table saw, for example"
JohnQ
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4th Aug 2021, 06:40 PM #13
Nigel I have a few solid 3 phase old stop buttons in the stash. Foot or knee style.
Dont want to go out in the cold atm to take photos as my left shoulder is throwing a spas
Happy to do it tomorrow if you’re interested.
H.Jimcracks for the rich and/or wealthy. (aka GKB '88)
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4th Aug 2021, 10:34 PM #14Diamond Member
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Thanks Henry. Take your time
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5th Aug 2021, 11:38 PM #15
Here’s a few.
All except the plastic red with the P on it are self contained boxes, that is a surface mount?
Most appear to lock in when pushed.
A few are all cast iron you probably could hit them with a hammer
When this latest covid f u is finished your welcolme to come over and grab what you need.
H.Last edited by clear out; 6th Aug 2021 at 12:00 AM. Reason: Adding photo
Jimcracks for the rich and/or wealthy. (aka GKB '88)
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