Recommended Setup PLEASE!

[eddie3000]

I am a complete newbie, and I would like to here your opinions and recommendations for setting up my g540 on my diy router. I hope this is be the right place to post this, if not SORRY!
I received my gecko g540 a week ago or so, and I have 57BYGH78-401A motors. They are rated at 2.8A, so I put a 2k7ohm current limit resistor. The motors get too hot IMO, I have measured about 75ºC after a quarter of an hour period of constant operation. Would changing the resistor to 2K reduce the heat? Is it a good idea?
Keling sold me a 48V 7.8A power supply, they said it was perfect for the g540. I don't know, but isn't it a little tight?
Another doubt I have is regarding the use of the 4 inputs and two outputs. I want to have homing switches on all 4 axis. So I guess that already uses up four inputs. If I wanted to use limit swithes independent from the home switches, would it be a good idea to have work in serial together with the e-stop?
At the moment I don't have a proper spindle, I am using a normal hand mini-drill with manual speed control. The only thing I can think of is using one output to activate a relay to turn it on or off, but I can't think of anything to regulate the speed other than manually. Any ideas?
Is an extra parallel port worth it for extra ins and outs?
There are so many possibilities that I don't know what is best. I would like to hear your opinions on what setup is better or safer or cheaper or whatever. For your info, I am a hobbyist, not a pro, and I'm just doing this for fun. Thanks!

[brtech]

There is a thread about overheated motors and G540s here. Where is your resistor placed? Is it on the connector that plugs into the gecko, or is it close to the motor? If it's the latter, then you may have the problem the thread discusses.

I think the power supply you have is adequate.

The home/limits issue is perplexing; I know I had lots of confusion at first.

You can, if you want to, and set up Mach correctly, do it with one input. You would have a combined home/limit switch on one end of each axis, and a limit switch on the other end of each axis. If you use mechanical switches, they are all wired in series. All this takes is to have Mach configured to home each axis separately, which is the default and configure combined home/limit (which allows Mach to override limit when doing the home operation).

You didn't say if you had a 4th motor for a double Y drive. If you do, then there is a good reason to have a separate input for the home of the 4th (A) axis; it allows Mach to square the axis when homing. On a smaller system, you only have one motor on Y and this doesn't matter.

I don't think there are really good reasons to use more inputs. You commonly see that people do use one input per axis, but the advantages are pretty small, and if you can use those inputs for more features (like a touch plate for example), I think it's just fine to combine all the home/limit switches.

I do like the electronic (hall effect) home switches. They are very accurate and repeatable. I have 4 x 4, with two drive motors. At the moment, I am using 4 inputs, but I'm going to move down to 2 inputs when I build a real mounting arrangement for my controller & power supply.

[eddie3000]

Thanks in the first place for your answer.

I am using emc2, not mach3.
I have placed the resistor on the driver side of the cable. The machine performs very well, it's just that the motors get hot, too much for my liking. My doubt is about it being alright in reducing the resistor value? Is it worth sacrificing torque for less heat?
About the homing switches, how can you use the homing switches all on one input? How does emc2 know when each axis is homed?
One thing crossed my mind, and that's whether the fault signal that the g540 sends through the parallel port also activates with the estop, or do you have to use a dedicated input for the estop??
Can I use NO switches (I already have a few), or should I get NC switches for the limits and homing?

[brtech]

Don't know much about EMC, so I may not be able to help you with that.
I don't know enough about the interaction between the G540, the resistor and the motor to advise you on what happens when you reduce the current.

In Mach, the home routine can be configured to home each axis separately. The home routine moves the axis to the point where the switch activates, then backs it off to the point where it is no longer activated. It can do that, sequentially on each axis, with one input. It only moves one axis at a time, and assumes that if the input changes state, it's the one for the axis it is moving.

The gecko has a separate input for E-Stop, that gets reflected up to Mach/EMC on the same input as it's fault signal. You don't need/want another input for that, but there is a school of thought that says E-Stop should kill the power to everything.

Yes, you can use NO switches. You wire them in parallel. The reason we usually use NC switches is that a wire break or other fault in the system manifests as a switch activation, which is fail safe.

OTOH, what kind of switch do you have that is NO only? For a mechanical switch, you want a "microswitch" or "snap-action". They are almost always SPDT. Usually, you use a roller mechanism on the lever. OTOOH, the electronic switches are NO, active low and we wire them in parallel.

[eddie3000]

Thanks brtech!
What I have is a dozen of push buttons, that do not latch. They are small and can be fitted anywhere.
The estop input on the g540 is meant for a NC switch, so my buttons are no good for that (unless I fit a relay and a small circuit).
I haven't seen anything on EMC2 that suggests it can do the homing in the way you say Mach3 does. I guess that's an extra point for Mach3 in that respect.
So I guess, unless anybody else comes up with another suggestion, I will have to use one input per axis home/limit switch, and that's that. Or I could do without the A axis home switch and put all the limit swithes in parallel together on one input.

[brtech]

Push buttons for limits might be okay. They may not be so good for home. You want a switch with a very positive on/off with some hysterisys, so EMC can drive it to on, and then back it up to off and have some accurately maintained repeatability.

This is the advantage of the electronic home switches, which have really great repeatibility, but a snap action microswitch isn't too bad. A random push button switch may not be so great. You can get snap action microswitches for a buck or two at Digikey.

I would get a real big mushroom E-Stop. Something you can bash really quickly. I found one on ebay for a few bucks.

[Hyrum R]

I wouldn't worry about the stepper motors being too hot. According to Gecko, you're fine up to about 85ºC.

Q.) How hot is too hot for a step motor?
A.) The maximum heat for most steppers is around 100ºC (212ºF), but it is generally never good to have the motor heat go above 85ºC (185ºF).