e-stop design
I've read everything I can here and on the web about e-stop circuit design. I think I get the theory and what I need to do to safely shut down my machine (A Grizzly G0704 CNC conversion). Now I am trying to make the design decisions for MY circuit! There are so many options and it isn't clear which are the most cost effect, safe, etc. Here are the devices/circuits I need to manage:
1) I'm controlling my spindle with a KBMM-125 which is in turn controlled manually with a POT and via Mach with a CNC4PC C6 board. 20Amp
2) my control box with a CNC4PC C35 BOB, stepper drivers, 48V power supply. the C6 board, relay for the flood coolant, 5V and 12V wall warts for the various devices. 15Amp
3) an 850 GPH 120V pump for flood coolant. 5Amp
4) e-stop signal to Mach
So, I need a safety relay to switch these off when interrupted by the e-stop. First, I find that these safety relays come in 24V and 120V options. It seems that a 120V safety relay would be simpler in that a separate 24V power supply would not be required. Is there a cost consideration (i.e. the 120V version is significantly more expensive?)? How about having 120V run through the e-stop switch. Many seem to be rated for that.
Second, since my spindle needs a 20A contact, what is the best way to deal with that? Are relays with four NO 20A contacts available and affordable?
Figuring out what's available for a cost effective solution is challenging!
cheers,
Michael
Reelsmith, Angling Historian, and Author of "The Reelsmith's Primer"
www.EclecticAngler.com | www.ReelLinesPress.com