Quote Originally Posted by PAULRO View Post
right guys, this is probably a dumb question but i ask it any way, if 1 switch can be used as a home switch and limit switch to monitor an axis ( that's 4 switches in total for X,Y,Z, including a separate switch for the slaved A axis home) why would some builders need 3 switches per axis , total of 10 including a separate switch for the slaved A axis home? if the limits are separate to the home would they not need an extra input to the already limited no. available on the LPT port? there is also a cost factor for the extra switches. i have to be missing something here.
My build so far has accommodation for an e stop hard wired to drop out the drives and as an input to the BOB for MACH 3. is there a need for a hard wired stop switch on the panel door? and if so how does it differ from an estop? I'm sure i can stop and pause the machine from MACH 3. is this adequate?
is it ok to use the main switch to drop out the power supply to the drives or should i have a switch after the power supply to control the drives and leave the power supply powered up when configuring the drives. does it matter?
i think i'm at a stage where i need to get the machine up and running with an adequate level of safety built in. i can then add the extras as i become more familiar and comfortable with the experience. any thoughts on the above would be appreciated.
Ok well couple reasons for 3 switches is if they wanted to home all axis at same time, Mach standard way would do Z first then Y then X which takes longer than if all Axis move at same time. Other reason is to have Home switch in a different place to limit switch.
If you want to cut down on Switches and Wire then just use 1 switch and have it travel with the Axis being tripped by targets at each end.

For DIY use then you don't need Hard wired door switch IMO but if you did want a Simple setup then Yes just run switch in series with E-stop circuit.
Correct way would be a Door contactor that won't let you Open door without turning power off but they are Expensive and OTT for DIY user with Common sense.

To me even in DIY use then Safety is still important but does need to be kept real.
If you use a Hardware Driven E-stop Circuit that disables power to anything that can hurt you using Contactors and relays then it's more than safe enough. You should never rely on software for Emergency stopping the machine.

Like I say Limits are not an Emergency incident so just Halting and prohibiting machine movement is ok.

If your unsure of how to build Safe E-stop system with Relays etc then let me know and I'll knock you something up.