Limit Switches with LED's

[manofgresley]

Hi Robin
My apologies if my protocol is incorrect.
I have attached a PowerPoint Drawing, which is my interpretation of your drawing, which contains everything i know so far. Would you be kind enough to go over it, and advise me if it would work or not?

Regards

Ray

[Shinobiwan]

Okay, attempt #2...

Sick sick drawing skills there Robin!

[manofgresley]

Hi Jazz

You know i think that i am a newbie to this world of CNC / Electronics. As previously mentioned i have a ZP54 - int Breakout Board, would you have a drawing for the HOME position switches or do they have to be configured in Mach 3 as software limits with the Stepper motor positions. I understand how this would work with Servo's but not Steppers.

Regards

Ray

[JAZZCNC]

Ray think you may be mixing up soft limits with homing and physical limit switches. Soft limits have nothing to do with Actual physical limit switches they are just a software version of a limit switch and use the machine coordinate system has reference.
In fact with soft limits defined which you usually setup to be just less than the machines physical hard stop range then it's very easy to crash the machine into the hard stops because when you RefAllHome without Physical Home switches Mach just Zeros out Machine coords where ever it's parked.
So if you happen to RefAllHome with the table or Gantry say towards the middle of movement range then Mach use's this Zero coord has the start point for soft limits and if for instance you set-up soft limits with a movement range of 500 positive before soft limits kick-in but you only have 400 physical movement left then Mach won't know and crash into stops.!!

Soft limits have absolutely nothing to do with home switches at all other than they share the same setup menu in Mach.

Personally I use separate Limit switches wired in series using one input on the Bob. Then have separate Home switch's wired in series using another input of the BOB.
You only need 1 home switch per Axis.

To set-up Home switches in Mach first set the input your using in Ports&pins/input-signals. You really have 3 options now.
If sharing LIMIT switches has home switches then set each Axis Home signal to the same input your using for limits from the BOB.
Same has above for separate Home switches if your using them wired in series just using the different input from BOB.
If using individual home switches then you'll need to set each Axis signal with the individual Input used on BOB.

Next in the Home/soft-limits menu set which way you want the machine to set off looking for the home position using the HomeNeg selection.
In this same Menu you can define other things like auto zeroing the DRO's after hitting switch and percentage of Rapid speed to home at.

Thats all there is too it.

[manofgresley]

Hi Wilfy

I agree, it should be obvious where the machine has stopped. I am a retired Mechanical Engineer. This is the first cabinet i have ever wired up on my own, so my learning curve has been near vertical, i just thought it would be a nice thing to do, as i have plenty of time on my hands, any help would be appreciated.

Regards

Ray

[m_c]

The plan above won't work as having just checked the datasheet for the BOB, the limit switch input is gets pulled to ground, so it won't provde enough power to light up anything, and adding LEDs in that way will probably be enough to pull it to ground.

Using some kind of high impedence sensing is the only way to make this work without affecting the BOB input.
For design/build simplicity and to avoid dealing with individual chips, I'd suggest an Arduino UNO. A quick sketch (arduino talk for code/programme) will do what you want easily, the inputs are high impedence by default, and it'll power LEDs easily.

[JAZZCNC]

Can't he just use a separate 5V supply and use the NO contact to make the circuit when the switch trips.? Simplizz enough to me.!!

Edit: Like this.?

Ray the same 5V supply that powers the Bob would work just take another feed from it.

[Robin Hewitt]

Or, use a double throw microswitch and have red green on every switch, fully independant and all on one 3 wire loop, easy peasy.

[manofgresley]

Hi Robin

Many thanks, still confused, would that be a SPDT? I thought I was trying to illustrate that in my drawing, or did I get that wrong?

Regards

Ray

[manofgresley]

Hi Jazz

Many thanks again, will this stop the machine from moving if activated.?

Regards

Ray