Wiring G540 and Proximity on CNC router

[chiefcnc]

I have a G540 and would like to wire 5 proximity sensors i have purchased.
Not sure how to do this as i have never had any sensors or limit switches on my cnc mnachines in the past.
I have attached the manual
Model # TKI8N2B Three wire.
Output mode NPN NO
Would all 5 proximity sensors have to be wire in parallel? I am a bit confused with which wiring diagram to follow in manual.
Thanks

[doorknob]

I have not yet hooked up limit switches to my G540, so what I am going to describe is based on reading the documentation only.

You should be able to wire all of the NO proximity switch outputs to a single G540 input in parallel, using the wiring diagram identified as "NPN parallel connection". Or, you could wire some of them in parallel to a single input and some others to individual inputs.

The output resistor labeled "R" in that diagram is actually built in to the G540 as the input "pull-up" resistor. With the output wire(s) of one or more NO switches wired to an input, the voltage on that input would normally be close to 12 volts, and that voltage would drop to near zero when any switch has been activated.

You will need to connect a positive power supply voltage to the +V terminals of the switches, and connect the minus terminals of the switches to the power supply ground terminal of the G540.

The question of where to get the +V positive power supply voltage for the switches will take some planning. Your best bet would probably be to find out what other G540 users are using to supply power to their proximity switches.

If I have read the datasheet correctly, the maximum power supply voltage for the switches is 30 volts. Many G540 users have something like a 48-volt power supply connected to the G540 power input terminal, and so if that's what you have, that is too high a voltage to connect directly to the proximity switch +V terminals. So you will either need to find a separate power source for the proximity switches (for example, a 24-volt DC supply) or else you will have to use a circuit that will drop the motor supply voltage to a suitable value.

If you decide to tap off of the 48 volt supply to provide power to the proximity switches, you would probably want to use a decent voltage regulator rather than a simple resistor to drop the voltage, to avoid any possibility of coupling motor-induced power spikes into your proximity switches. I don't think that you can get by with a simple 3-terminal 24-volt regulator such as a 7824 type to do the job, because 48 volts is probably higher than the maximum rated input voltage for those regulators.

[john_100]

Hi chiefcnc ,

just connect the switches in parallel as in the diagram


John

PS if you want to add led indicators to each switch
just connect each switch output via a diode to the G540 input
( one for each switch)
see Roman Lini's thread diy limit switch thread :-
Electronic home switches made easy!


PPS
to use a 7812 or 7824 to drop a 48V supply down to supply the limit switches you will need a simple pre regulator (eg zenner and dropper resistor)
- the maximum input voltage for the 7824 is 40V and for the 7812 is 35v

[chiefcnc]

Thanks for your help guys. I will be purchasing this power supply New 24V 2A 48W DC Switch Power Supply Driver For LED Strip Light Display #17 | eBay

to wire the proximity sensors. I do have enough room in my current enclosure to have this and my 48v power supplies. Is it possible to connect both power supplies together - From one power supply to the other -Positive to positive mains / earth to earth / negative to negative?
I have also connected a external chassis mounted DB9 to the G540 inputs 1-4 and to V+ so that i can connect the sensors to. So to confirm will i still need to wire in resistors? I was hoping it was a easy direct wire in to the DB9.

Thanks

[doorknob]

Thanks for your help guys. I will be purchasing this power supply New 24V 2A 48W DC Switch Power Supply Driver For LED Strip Light Display #17 | eBay

to wire the proximity sensors. I do have enough room in my current enclosure to have this and my 48v power supplies.

That should do the job for you.

Is it possible to connect both power supplies together - From one power supply to the other -Positive to positive mains / earth to earth / negative to negative?

Just to be sure that I understand you, you're talking about paralleling the AC inputs to the power supply, and by "positive mains" you mean "AC hot wire" and by "negative to negative" you mean "AC neutral", right? That's the way that I would describe it with US power wiring anyway, not sure about Australian power. If so, that should be fine, although you may want to get more sophisticated, for example with separate fuses in the 'hot' leads, one or more power contactor relays possibly controlled by an emergency power off switch, and the like (but that is all beyond the scope of the question that you are addressing now).

I have also connected a external chassis mounted DB9 to the G540 inputs 1-4 and to V+ so that i can connect the sensors to. So to confirm will i still need to wire in resistors? I was hoping it was a easy direct wire in to the DB9.

The G540 inputs 1-4 are taken from a terminal strip, and you will be wiring them directly to the DB9. According to my reading of the proximity switch hookup diagram, you do not need to hook any resistors to those terminals. The resistor shown in the diagram posted by john_100 is the same "pull-up" resistor internal to the G540 that I mentioned in my post above. That diagram shows the G540 inputs as optoisolated, and the resistor is in series with the LED of the optoisolator. You do not need an external resistor, because that one should be fine as it is.

Note that you will also need to wire a ground connection to the DB9 from the common power supply ground terminal of the G540 (because you will need to connect the -V terminal of each switch to ground). I would not trust the DB9 shell to be that ground, although you might consider connecting one end of the shield of the wire going to the the switch(es) to the DB9 shell (if you are using shielded cable and a metal connector shell and if the chassis mount DB9 is connected to a grounded metal chassis).

[john_100]

Hi chiefcnc ,

any reason why you are using a 24V supply instead of 12V ?

I'd not expect you to need any resistors when wiring all of the proximity sensors in parallel to one G540 input
(unless you add a LED indicator)


John

[chiefcnc]

That should do the job for you.





Just to be sure that I understand you, you're talking about paralleling the AC inputs to the power supply, and by "positive mains" you mean "AC hot wire" and by "negative to negative" you mean "AC neutral", right? That's the way that I would describe it with US power wiring anyway, not sure about Australian power. If so, that should be fine, although you may want to get more sophisticated, for example with separate fuses in the 'hot' leads, one or more power contactor relays possibly controlled by an emergency power off switch, and the like (but that is all beyond the scope of the question that you are addressing now).

Yes that is correct. I have a emergency switch on the AC hot wire between the main on/off rocker switch and the AC input on 48v power supply. This would also cut power to the other power supply.



The G540 inputs 1-4 are taken from a terminal strip, and you will be wiring them directly to the DB9. According to my reading of the proximity switch hookup diagram, you do not need to hook any resistors to those terminals. The resistor shown in the diagram posted by john_100 is the same "pull-up" resistor internal to the G540 that I mentioned in my post above. That diagram shows the G540 inputs as optoisolated, and the resistor is in series with the LED of the optoisolator. You do not need an external resistor, because that one should be fine as it is.

Excellent. Less is better when you are new to the world of electronics.

Note that you will also need to wire a ground connection to the DB9 from the common power supply ground terminal of the G540 (because you will need to connect the -V terminal of each switch to ground). I would not trust the DB9 shell to be that ground, although you might consider connecting one end of the shield of the wire going to the the switch(es) to the DB9 shell (if you are using shielded cable and a metal connector shell and if the chassis mount DB9 is connected to a grounded metal chassis).

Cheers.

[chiefcnc]

Hi chiefcnc ,

any reason why you are using a 24V supply instead of 12V ?

I'd not expect you to need any resistors when wiring all of the proximity sensors in parallel to one G540 input
(unless you add a LED indicator)


John

No reason. It was the first one i found on ebay. I also found this one which is 12v
DC 12V 2A 24W Switch Switching Mode Power Supply Driver For LED Strip Light Lamp | eBay

Cheap! We almost pay this much to send a letter in Australia