[kolias]

I’m looking at a wiring schematic for the G540 and besides the enable switch which is connected on pin 10 there is an E-Stop on the AC line feeding the switching power supply unit.

I remember reading somewhere that it is not a good practice to cut the AC power on stepper motors.

So where do you put the E-Stop?

[john-100]

Hi Nicolas ,

the problem is if you disconnect the DC supply to the G540

the E stop in the AC supply to the power supply
is just another on/off switch thats easier to switch off in a panic

the E switch connected to the PC will stop the stepper motors quicker
provided the PC is still responding

but the E stop in the mains supply is guaranteed to stop every thing
once the stored energy in the power supplies has been used up

http://www.homanndesigns.com/pdfs/EN010_V8.pdf

John

[kolias]

Thank you John for the info, I do have this wiring schematic, very nice work,

So now how do I calculate the fuse size on SW-06? My DC power supply will be 36V / 10A and the AC line in Canada is 120V. (I just happen to have the 36V/10A switching power supply unit and I will use it for now and perhaps later I will get a 48VDC / 10A unit)

[john-100]

Hi Nicolas ,

I would of expected the fuse rating to be printed onto the power supply

but with an output of 36V at 10A = 360w
excluding any losses you need a mains input of 120V at 3A

if due to losses within the power supply the output is only 80% of the input you will need a 4A fuse
its possible due to the switch on surge current
you may have to use a 5A fuse

HRC ceramic fuses are best as they stay in one piece even with
very high fault currents

John

PS had a quick search and it looks like you need a 6.5A fuse
the surge current is larger than I first expected

http://www.ebay.co.uk/itm/36V-10A-36...item2c64e26854

[Al_The_Man]

You may also want to check in the P.S. itself, many are fitted with an on board fuse in the L1 conductor.
If you have any other 120v loads in parallel you would have to fuse accordingly.
Al.

[john-100]

Hi Al

good point about additional loads

I overlooked the spindle motor

the largest fuse you can for an IEC connector is 10A

once the stepper motor supply has been switched on
you have about 6A available for the spindle motor and its speed controller etc

with a soft start , and a 120V supply , that probably limits you to a
500/550W motor
thats if you don't use a separate mains supply for the spindle

John

[kolias]

Sorry kind of complicated for me, electricity is not my strong field…

Never used my 36DCV /10A unit and don’t know if it has an internal fuse. All it is written on the unit is:
MW, S-350-36, 115VAC 6.5A 230VAC 4.0A, 50/60HZ. The DC Voltage is adjustable but never try to see by how much.

This unit will not feed the spindle because I plan to have a Hitachi X200 VFD. My 4 steppe motors are STP-MTR-23079, 276oz.in, 2.8A, 3.82mH, 1.10 ohms and I don’t plan to feed anything else from this power supply.

So a 5.0A fuse will be sufficient on the AC line?

BTW what kind of connector is the IEC?

[Al_The_Man]

IEC Connectors - Full range of quality mains rated inlets, outlets and connectors with electrical ratings upto 20A 250V by Bulgin Components
How do you intend to E-stop the spindle?
One of the ideal E-stop circuits is to have all the N.C. E-stop functions in one low voltage sourced string with the end result as a small control relay of which on contact will cut the AC power to power relays or contactor(s) that cut power to the coil voltage.
This relay would also advise Mach or other controller that a E-stop had taken place.
Al.

[kolias]

Al, I don’t know yet how to E-stop the spindle and the purpose of this post is to get ideas on how other members achieve this function.

One way is like what John said on post #2 with the schematic from homanndesigns. This schematic has a VFD connector which will send a signal to VFD to cut the power (I think) and therefore stop the spindle and let Mach3 know about it. Since I don’t know enough about electronics, I must understand and feel comfortable with a schematic before I proceed and that is another reason I started this post

[kolias]

Can someone help me understand the homanndesigns wiring schematic from post #2 ?

The way I read it, the AC line comes in at the IEC Plug on SW-06. From this switch we go the the 48V power supply unit plus to the IEC Female Socket and from this socket to RL-04

I see that SW-06 is a double pole switch. Can this switch be a regular household switch? Why it has to be double pole?

Why I can’t wire directly to the RL-04 from SW-06 ?.

What is the purpose of RL-04 ?

Regarding the Enable Switch to pin 10, is this a regular on/off switch or an E-Stop switch?

[john-100]

Hi Nicolas ,

the enable switch to the G540 terminal 10 is used by many people
as the E stop switch
IF the PC is responding correctly
Mach 3 software will stop sending step signals and
switch off relay RL-04 to remove the mains supply to any thing connected to the IEC socket
( no good if a spindle motor or the psu is emitting smoke signals )

in my case it will be for Mach 3 to switch the spindle motors speed controller on and off
when I convert a mini lathe to CNC
but I'd go for the E stop switch directly controlling the mains supply
and not via the PC

if you don't have a E stop switch with the correct switches
to safely switch the mains supply to the motors
and via the G540's terminal 10 an E stop to Mach 3
as Al suggested you can use a relay / contactor
to keep the safe low voltage circuits and the mains separate

the choice of E stop you use will depend on the damage that can be done to you and the machine when things go wrong

as for sw-06 being a double pole switch
a double pole switch ensures the machine is isolated from the mains supply
it disconnects the live supply even if the mains wiring is crossed
as can happen with a non polarised mains plug
the choice of switch for the G540 enable (terminal 10)
depends on how you want to use it


John

[kolias]

Thank you John for the help

If I understand correctly the homanndesigns schematic has 2 E-stops, one (the Enable) is providing a stop function to the motors through Mach3 and is required for the G540 to function properly.

The other E-stop is SW-01 which is cutting the AC power to the 48V unit. So with these two E-stops I will assume that I have a good protection.

Sorry but I don’t understand what Al said on post #8. What is a relay / contactor?
and how you can keep separate the low voltage circuits and the mains?

[kolias]

......This relay would also advise Mach or other controller that a E-stop had taken place.
Al.

I don't see an input pin on the G540 to advise Mach that a E-stop had taken place.

So where do I connect the signal to tell Mach that an E-stop has taken place?

[john-100]

Hi Nicolas ,

the E stop input to the G540 is terminal 10

in the diagram from Homann designs its the "enable switch"
linking terminal 10 to terminal 12

in post 16 ,its half of the N/C E stop switch in my diagram

in the G540 manual its labled as the "disable( E stop)" connection to
terminal 10

this E stop signal is combined with signals from the charge pump /watch dog detector circuit and current overload protection circuit

provided terminals 10 & 12 are linked and no fault is detected
an optoisolator connects printer port pin 15 to ground pins 18 to 25

Mach 3 monitors printer port pin 15 to check it is at a logic 0 (low)

John

[kolias]

My apologies John but I never noticed your schematic in post 16. Thank you for taking the time, it is simple and easy to understand this kind of schematic.

And now I get it how Mach3 gets the input

On your schematic why you have 270 Ohms resistors on the 36V line?

And what is the thing on the bottom relay next to the 24V relay connecting the +24V and -24V lines, perhaps a diode? And why?

[john-100]

Hi Nicolas ,

the 270 ohm 1 Watt resistor is to drop 12V so a 24 V relay with a 576 ohm coil can be connected to your +36V supply to the G540

yes that is a diode connected across the third relay
it provides a path for the back emf when the E-switch opens
with out the diode the arc inside the switch will shorten its life
if you use a diode like the 1N4001 , connect the cathode marked with the white or silver band to the positive supply (use any from 1N4001 to 1N4007)

http://www.vishay.com/docs/88503/1n4001.pdf

the third relay and a low power 24V power supply is only needed if you use the low current SW-05 E-stop switch to switch the mains supply to
the 36V power supply for the G540

a 24V @ 100mA power supply will be enough to power the E-stop relay
eg POWER SUPPLY 24VDC OUT 100MA - PW2-24

to power three relays you need a 24V @ 200Ma power supply (if you don't power 2 relays from the 36V supply)

with the low power 24V supply for the e-stop relay added
you have a choice of how you power the relays controlled by the two
G540 outputs

you can power them from the 24V supply without the resistor
or the 36V supply with the resistors
check the coil resistance of your relays is about 540 to 600 ohms

John

[Al_The_Man]

Here is one example from a old project, if you notice, the control relay ERL has a 24vdc coil and is responsible for switching any 120v or 24v power devices that are required to be off in a an E-stop condition, check the occurrences of ERL contact, you may not need that many, the E-stop string itself only shows a couple of actuators (P.B's) but in fact can have as many actuators you wish in series that would need to initiate an E-stop, such as N.C. limit switches or watch dog timers etc, in the case of Mach type controls, an auxiliary contact on ERL could be set up as the E-stop input into Mach to advise an E-stop has taken place.
If you bring the main power to the system through two AC conductors then it is much easier to switch and control one AC power source rather than everything plugged into separate receptacles.
The circuit also show the push maintained type buttons, but the method mentioned by John is preferred where there is a N.O. start PB and you would need a N.O. contact on ERL in parallel with the PB to retain it.
Al.

[john-100]

Hi Nicolas ,

in the Homann design circuit the E stop switch controlles the 48V power supply for the G540 and the 48V relays

the simple solution would be for you to use 36V relays instead
but I've not found 36V versions of the 48V relay from Homann Designes
Farnell sell a 24V version that you could use either by connecting a 270 ohm 1W resistor (approx half the coil resistance , 576/2=288)
in series with the coil or using an additional 24V DC power supply for the relays (24V at 42 mA per relay is enough)

Power - General Purpose | Farnell United Kingdom

search for flange mounting relays ,then go to page 3
(not sure why the long link to the page didn't work)

the next question is do you want the E stop switch to connect the G540
enable input to GND

the SW-01 E stop switch on the diagram has one N/O contact and one N/C contact
but the smaller DPDT SW-05 E stop switch from Homann Designes
can be wired as two normally closed contacts
one for the G540 enable and the other to switch on a 24V relay controlling the mains supply to the G540 power supply

John

[kolias]

Lots of information in the last two post, thank you both

I have printed the PDF files and I have to study them to understand well.

Along with my order from Soigeneris I also have three 24V relays coming and perhaps they will be suitable for what I want to do.

Sorry but I don’t know what will happen if “do you want the E stop switch to connect the G540 enable input to GND”.

I like the idea of the SW-05 E-stop with the two NC contacts but I don’t know how practical this will be because by pressing this switch the power to G540 and the AC line will go OFF meaning that everything will go dead.

On my previous two cnc I had only one E stop which was only telling Mach3 to stop the motors. I found this set up was convenient but perhaps not safe.

Bottom line is that I think the HomannDesign schematic is what I would prefer; the enable switch will only stop the G540 (and I guess the motors) and for a real emergency SW-01 will cut the AC power to everything. Is this considered a good strategy?

[john-100]

Hi Nicolas ,

as I understand it
the G540 sends an E stop signal to the mach 3 software
when the stop switch connecting terminals 12 & 10 goes open circuit
or the 12Khz charge pump signal is missing

all outputs are switches off by the G540's E stop and charge pump detector circuit.
the stepper motors free wheel , the relays connected to outputs 1 & 2 switch off and the 0 to 10V control voltage to the spindle motor speed control is set to zero

I'm not sure why you think switching off the mains power and signaling an
E stop to the G540 with the same switch could be a problem

but when building your own machine, there is no reason why you can't use two switches if you prefer it that way


John