I am nearly done with my build and have started wiring the black box up. The info I have found says to wire the limit switches in the NO position. Can I wire them in the normally closed position with the Black Box???
NC is best practice with limit switches. BlackBox runs grbl, all the info is here: gnea/grbl Which way you go dictates your $5 config value.
Depends which switches you have (we have two types) If you have Xtension Limits, no, they are NO only, BUT comes with onboard RC filters!
I have the same question. NO or NC? Just plain limit switches that can be wired either way. While I appreciate the link to gnea/grbl, that is assuming that I am interfacing to an Arduino Uno. I am interfacing to a black box control.Unfortunately the black box documentation does not delve into which is better NO or NC, nor does it address putting limit switches on both ends of an axis. While it is a very pretty picture, and it looks like maybe it is suggesting NO (85.27% sure), my 50 year old eyes can't tell the difference between an O and a C that small - sometimes words help too In any case, am I to assume that the following is correct (substituting each respective SIG line for 9, 10 & 12 lines)? Lastly, is the active noise filtering recommended for a machine with a 3' x 2' footprint as shown below? Or will I (most likely) be ok using twisted pair / shielded wiring? If so, should I tie each cap back to it's respective Axis ground line?
The BlackBox "Brains" board is just an Arduino Uno in a slightly different package for more convenience of use, but it works exactly the same because it's designed to run grbl exactly the same. Hence why you get links to gnea/grbl. As Peter says above, OB limit switches are NO. They use on-switch RC filtering to eliminate the noise (the filtration should technically be as close to the Arduino pin as possible, but maybe Peter added some more capacitors in there as well? Probably doesn't make too much difference on most small machines). The +5V line is to run the helpful LED indicator, and maybe the auxiliary pull-up resistors in the RC filter per the above diagram, but they don't technically need it. The SIG lines do literally go to what the ATMega328P microcontroller inside the BlackBox understands to be pins 9, 10 and 12. Like I said above, NC is technically best practice, however. If you rewired the switches or used your own switches to run NC, you'd have to tell grbl that it should be looking for that different signal in the $5 config (because "Arduino" has to internally change those pulldown resistors, pretty sure). I didn't use NC on my laser, though, just did shielding+caps and it has been fine. I would strongly recommend shielded wire and at the very least 104 ceramic filter capacitors near or at the BlackBox plugs. I've had no end of trouble any time I haven't done both. Resistors are up to you. These types of machines are really supposed to use 24V signals, not 5V. The pretty picture does indeed say NO on the switch connections, btw (I can barely see it either).
Wow, thank you for the very thorough and fast explanation and knowledge sharing (I had no idea BB was at it's core a Arduino Uno - what's that saying ignorance is not an excuse ). I've got 2 conductor twisted pair shielded cable on order, caps I have. Again for clarity, cap goes between SIG and ground, (drawing shows cap between SIG and ground and then continuing to resistor to 5+) I could wire right at plug if I read correctly......
I imagine Peter doesn't advertise that fact too heavily because it probably makes people underrate BlackBox as a concept. From what I've seen, the components, their specs, the additional IO, all together in one package are well worth what is charged for it. You couldn't build something of equivalent quality for less than around the same price, and would have a harder time interfacing with what they did get. (I know, because I don't use BlackBox!) Here's a pic of my "GreyBox" with the caps right at the terminal plugs: The terminal socket PCB wires straight to the Arduino Uno terminal block breakout board I made in there, nothing else in between. Those are, as you can see, between each individual signal wire and ground separately, with some 1/16" heatshrink for appropriate lead insulation. It's a little kludged together, could be much neater and internal on the Arduino shield like the front control button filter caps are, but it does the job so I'm happy. The idea is simply to shunt those high frequency noise signals to ground, and the capacitor at that particular size has very low AC impedance to them, so that's the preferential route to ground vs going through your DC signal chain.
Yes, BlackBox also has onboard RCD noise filtering even for normal switches. Though we do highly recommend the Xtension Limits. Easier to wire... wiring the other type wrong is easy and shorting v+ to Gnd is a quick way to kill any electronics.
just parallel them up. Easy because its NO, Nc wiring is harder to understand blackbox > sw1 > sw2 Sig > sig > sig Gnd > gnd > gnd V+ > v+> v +
Hi Peter, For clarity, I have an Openbuilds Black Box, your high torque steppers as well but "standard" limit switches. I have the 4 conductor wires included with the stepper motors, but I also have some shielded 4 conductor wire and also shielded 2 conductor wire that I was planning to use for the limit switches. I have a 220V VFD and spindle for my machine. Where should all these shields on the wires be connected to? Or are shielded cables not required for the stepper motors and limit switches as long as my VFD cable is shielded and connected at one end (to ground)?
In a star-ground configuration, to a central point, and from there typically to a physical earth (spike or copper pipe into soil outside the shop) BlackBox has onboard RC+Reverse biased diode noise filters, but noise can get into the system from other sources than just the limit switch wiring. That's why you run the VFD cabling itself far from everything else (including the mains input to the VFD) Stepper motor wiring near limit switch wiring (or any other low voltage wiring) can also induce EMI Theoretically yes, the VFD is the source of the problem. Shielding everything around it is a workaround, properly earthing and shielding the VFD is the better strategy: See section 2.8 of the BlackBox documentation: docs:blackbox:faq-emi [OpenBuilds Documentation] In particular, at the bottom of that paragraph, it links to which digs deep into the very technical depths
I just bought a Lead 1010, which includes Xtension Limit switches. I have a Mach3 USB controller board with opto isolated IN1-IN4. I'd like to keep 24VDC signalling. Can I parallel wire the X & Y axis limits in so that IN1 are these limits, IN2 is Z Max limit, IN3 is E-Stop, and IN4 is Probe? Do these limit switches drive high or pull low when activated?
Xtension Switches are Normally Open, and connects Signal to GND (LOW) when triggered See docs:blackbox:jumper-limitswitchvoltage [OpenBuilds Documentation] Xtension Switches does support 5-24v Refer to your controller's manuals or support contacts. As its not a BlackBox, I cannot confirm, on a BlackBox, you can parallel SIG on controller, to SIG on switch1, to SIG on switch2, and repeat for V+ and GND
