[cncneon]

Early stages of learning Mach3. After getting the steppers to move correctly I quickly realized
a panic E-stop would be a handy thing. . . .
Attached is a pic of my BOB and where I hooked the switch. Cheap import that has 2
sets of contacts, N/O & N/C. Tried it both ways, no go. My setting under pins & ports are

Enabled......Port.....Pin #....Active Low.....Emulated......Hot Key
...../.............1.........10............../..................X.................0

What am I missing? All help greatly appreciated.
cncneon

[john-100]

do you have the 12 to 24V DC supply connected to the BOB ?

I traced the BOB's circuit to answer another post a while ago

Attachment 416024

the USB connector powers the two 74HC245 IC's and the relay

the 12 to 24V supply powers a 10V regulator (LM317 set to 10V)
the 10V output powers the 5 opto isolators that are connected to printerport pins 10 to 13 + 15 and the PWM to analogue converter

John

[mcardoso]

I want to make an important comment about Emergency Stop circuits with Mach 3 and 4.

The emergency stop signal into Mach is a courtesy signal which lets the PC know that an emergency stop has been executed. The PC should not be trusted to safely stop the equipment since software can hang, or signals can be messed up coming into the PC. The ESTOP must disable the machine at the hardware level. A simple circuit would be a stop button energizing a DPDT relay. One set of the relay contacts would energize the enable input on your stepper/servo drives, while the other would tie back into mach. In this way, if you were to hit the button, even if Mach still told the drive to run, the enable signal would be off and they would not move.

For years I just used the software ESTOP, and I did find on one or two occasions that the ESTOP function failed to operate correctly when used this way.

EDIT: Your ESTOP also should use the N.C. contact on your switch. This way if a wire is cut or comes loose, the system will fail into a safe state. A failed N.O. circuit could go undetected until you operate the ESTOP and find it doesn't work.

This is not much effort to do and will be safer for you and your equipment.

[Al_The_Man]

Agree with mcardoso, the E-Stop should be a hard wired circuit where all E-stop (NAND) functions are in series with the e-stop relay coil, and as mentioned the Mach input is a courtesy warning that a hard e-stop has taken place, it is also a good idea to place the output of the watch dog or charge pump in the series string, in order to effect a E-stop if the PC freezes etc.
Al.

[cncneon]

[QUOTE=john-100;2276812]do you have the 12 to 24V DC supply connected to the BOB ?

No. My 24 V pwr supply is hooked to the drivers. Am I OK to just tap onto my exsisting PS? I have open pins.
Thanks for the expanded schematic on my BOB

Copy to the next reply about using the N/C setup with a relay hooked directly to the hardware rather than thru the
computer. I'd planned on going N/C but had not considered bypassing Mach3.

Appreciate all the help
cncneon

[john-100]

Hi cncneon

yes you can connect the BOB to the same 24V supply as the stepper drivers

once you have mach 3 seeing the E-stop you can look into adding a hardware E-stop as mcardoso and Al has referred to

John