Sure, the USB interface has a place for 4 axes of limit switches.

Each axis can have two limit switches: one for the ++ (positive) end and one for the -- (negative) end. The positive end would be the limit switch at the end of the machine that, say the machine has a 4'x8' area, reaches a bit after the 8 foot mark. The negative end would be the limit switch behind the 0 foot location behind the origin. If the origin is in the middle, the negative would be at a little more than the -4 foot end and the positive would be at a bit more than the +4 foot end. Note that you can have more than one switch on each pin where the NC is connected in serial fashion and the NO is connected in parallel fashion (this can be seen on the diagram in the multiple limits switch section). The software configurations for the limits switches are under File -> Settings -> Limit.

A typical limit switch has three connections on it. These connections consist of COM (common), NC (normally closed) and NO (normally open). The COM would generally go to GND and the NC or the NO would go to the pin. If the NC is used, then the the switch is constantly connected until the switch is pushed (engaged) then the connection from the pin to gnd is broken (open). Use the settings in software to set whether in NC or NO configuration.

Let me know if this information was helpful (or not) by adding information to this question. Thanks.

User response:
Thank you very much for this helpful information. I'm still a little fuzzy on how the 6 limit switches physically connect to each other and to the USB breakout board. You've stated one switch (home) goes to positive and another switch (limit) goes to negative. Are all the GND prongs from all 6 switches connected to each other and going to GND on the breakout board, or no? And the NC prongs, how exactly are they connected to each other? And to the board? There has to be a diagram somewhere shows this visually, no? I don't know how to wire the switches in series or in parallel. I have already physically installed all the switches on the machine and ran the wires to where the board is. Now I just need to know where to plug these wires into the board. Also, taking into consideration that I'm using the Planet CNC software, the only settings I have pertaining to limit switches is "Enable/Disable" for each axis, and the actual limit for each axis. Nothing about NC or NO. Is that only in Mach3?
Thank you.

buildyourcnc response:
On the USB interface, the COM on the switch connects to GND and the NC or NO connects to the input pin (i.e. x++, y--, etc.)

Limit switch configuration is rather difficult to understand, especially with series and parallel. You can think of series as a single wire going from GND to the axis letter input terminal (i.e. X++ or X--). If the wire is broken, then the circuit is open (or the switch is engaged in a normally closed scenario). Normally closed is like an actual wire, and when engaged, the switch "opens" (breaks the wire). This is why we recommend in some systems that you can put many switches in series on a single pin. When one of the switches is engaged (breaking the connection) then the entire circuit of switches is broken and the machine stops.

In a parallel scenario, the state of the circuit is always broken until the one of the switches is engaged and the circuit is then closed or connected. The topology looks like a ladder. All the switches connect to both sides of the ladder and the switches are like the runs of the ladder (the horizontal bars that the feet are placed while climbing). Imagine all of the switches broken in this scenario (normally open). It would be like the ladder could be split in two, but if one of the ladder runs (switches) is closed by engaging it, then that run would connect both sides of the ladder and the two sides of the ladder would have a connection.

There is a diagram on the USB page of the various limit switch configurations. If you need more information (visual and/or otherwise), please let us know and we will immediately add that information to benefit everyone.

Click the link to add information to this solution:
I have nearly completed the CNC machine from the book, but I am using it with a USB breakout board, and have no idea how to wire the 6 limit switches to the board. I'm having difficulty following the diagram on the USB breakout board screen. Can someone please help me?

We are currently working on a relay board that will connect to USB breakout board, and the router/spindle for both the on/off function. Unfortunately we still do not have it completed or ready to be placed on our website, but it is in the final stages of testing. Please check back regularly for updated stock!

Here is a link to a tutorial for a DIY relay circuit:

Click the link to add information to this solution:
I AM PUTTING TOGETHER THE BLACKFOOT AND USING A PORTER CABLE ROUTER. CONFUSED ON HOW TO RELAY ROUTETR WITH USB BOARD. IS THERE ANOTHER SWITCH THAT GOES BETWEEN BOARD ROUTER SO PLANET CNC CAN TURN PERHAPS VACUUM OFF?

WE don't have an actual file that contains the instructions for the machines as they are a part of a larger database file that is queried during the product page's rendering in the browser. The best option would be to print the webpage on a printer and use that as notes.

I know this will not provide larger images, but you could use the paper version to write your notes while assembling the machine using the larger images on the website.

Click the link to add information to this solution:
On the blackFoot 4'x8' CNC machine do you have the instructions under one file that I can download, I want to print them out and make notes as I am building the machine.

Consider the loads on each axis when choosing appropriate stepper motors. If your holding torque is maxed out at roughly 16oz/in (1lb/in), then you could use the NEMA 11 or 14. Also consider the shaft sizes and current ratings when choosing drivers that pair with the motors.

Click the link to add information to this solution:
I am planning to build a scratch CNC machine to do rotary engraving on writing pens. Can you recommend the parts I would need? I'm thinking NEMA 14 (11?) and 3/8" acme rod. Not sure which linear motion to use. I have an old lathe to use for the 4th axis.

Absolutely, I can answer this type of question and anything other questions you may have with your new-to-you CNC router.

Additional Information:
20

Click the link to add information to this solution:
[789] Can you help me with selecting a power supply ( and a few other components ) for the stepper motors that came with a homemade CNC Router I just purchased.

Sure, connect O2 (output #2) on your mach3 USB board to the GND side of your relay coil. Connect the 24V power supply to the positive side of your 24v relay.

You will want to connect a flyback diode (1N4007) between the coil connections to make sure the coil back current does not damage the Mach3 USB board.

Refer to this diagram:
https://www.buildyourcnc.com/Documents/Electric%20Wiring%20Diagram.pdf

Please let me know if this helps and if you need further guidance.

Thanks

Click the link to add information to this solution:
I recently purchesed a USB Mach3 breakout board and need help setting mach3 to use a relay to start the router can you show how to set the pins and which port to use on the board to attached the relay?

Yes, we can make a redLeaf system that has all 6A drivers for use with the 651 oz-in motors. We can also wire the electronics in a way that two of the drivers will use the pins of the same axis so that axis will drive two drivers and motors.

Click the link to add information to this solution:
I am building a machine that requires 2 steppers to drive the Y axis, can you make me a redleaf system using the 651oz steppers that will work for me?

What is the weight of the gantry, number of teeth on the drive sprocket and tooth pitch?

Click the link to add information to this solution:
I build a 3 axis router CNC the gantry is heavy in aluminium plate, witch plug n'play kit you suggest me 1 or two motor on the longest axis this will be drive with chain?

Ok, sure. Let's get the discussion started. Please respond with your questions on this FAQ

Click the link to add information to this solution:
Hi, I am thinking of making a CNC router that I can use in woodworking. I am very happy if you can help me with the necessary parts for this

If the sensors are NC (normally closed) you can wire them in series. If the sensors are NO (Normally Open) you can still wire them to the same input, but the wiring needs to be in parallel (like a ladder). I have more information on the following video:

Click the link to add information to this solution:
[788] Thanks for the oportunity to ask, I am building a cnc and using npn closed sensors could you help me with the conection of these, do i still connect them in series if i use more than two in each axis. Also you mention that a stop switch should be connected grd and input to the controller would that be done after the 24v power supply. Thanks r

The Mach3 USB will not work with Linux CNC. You can use our parallel breakout baord instead (if you have a computer that has a parallel port available).

Here is the link to that interface:
https://www.buildyourcnc.com/item/electronicsAndMotors-parallel-breakout-relay

Click the link to add information to this solution:
Hello. I'm currently building my first CNC router, and I'm powering it with a 3 axis electronics kit that was purchased through your site. I chose to get the Mach 3 USB Breakout board, but now I'm wanting to try to use Linux CNC to work with the computer I have available. Will that work with this board?

We are currently working on a relay board that will connect to USB breakout board, and the router/spindle for both the on/off function. Unfortunately we still do not have it completed or ready to be placed on our website, but it is in the final stages of testing. Please check back regularly for updated stock!

Here is a link to a tutorial for a DIY relay circuit:

Click the link to add information to this solution:
I am putting together the Blackfoot and I am using a porter cable router. I am confused on how to relay the routetr with the USB board. is there another relay switch that goes between the USB board and the router so that planet CNC can turn the router and perhaps the vacuum on and off?

Yes, you can preset an origin by zeroing the machine at the desired location before beginning your work. You can return to that exact point at any time, or you can specify an offset from that point to be the beginning point for the next machine operation (for instance when cutting several parts from one sheet of wood.) Jogging time varies by machine and application but would generally be a rapid move -- our default rapid setting is 400 inches per minute.

Click the link to add information to this solution:
Can you preset an origin point on this cnc? How long does it take to jog over? (If I have the case that I using the same thickness of maple wood, and same jig everytime)?

No, the 3.1 version will not support slaving the X axis. You will either need to wire the two x axis driver to the same X signal pins, or use the DDCS v4.1 which does support slaving an axis.

Click the link to add information to this solution:
[823] I plan to use a DDCS stand alone controller for a CNC router build which will have two stepper motors on the x axis, one on Y and one on Z. Will the 3.1 version handle two motors synched on the X axis or will I need the 4.1 version?

Attaching two motors in parallel is possible, but you will need another motor and driver for the opposite side. Each motor must have its own driver to work accordingly and fluently. The two can be wired together, to the same pins on your breakout board and set the dip switches on the driver to match the ones on your x-axis(ex). But remember to view the orientation of the motor and which way it spins, since it is on the opposite side it will have to be orientated correctly to move in sync with the other motor.

Click the link to add information to this solution:
I just finished building my first CNC with the electronics I purchased from you and I am already thinking about improving it. I would like to build a 2 motor X axis solution. Is it possible to attach 2 parallel motors and drivers to the BlueBrew Breakout Board? If so, how?

Dealing with our USB BoB, the potentiometer that will be used in the key jog, is a 5V, 5k - 10k Ohm potentiometer.

Click the link to add information to this solution:
I am building a cnc mill using your USB controller and i would like to know what is the specification of potentiometer used for adjusting manual axis jog speed

Yes, if you give us a call, we can definitely help you. If you are looking to mod one of our 4'x8' machines, we can provide those changes for you. We have experience with meeting customers' needs where their application requires a machine with small or even large changes.

Click the link to add information to this solution:
I am looking to build a cnc router that will cut 4x8 i wanted to get a cnc kit with some mods i was wondering if there was someone in sales that can help me

Do you believe the source backlash is at the nut, or somewhere else?

Click the link to add information to this solution:
Hi Guys, I fitted new ball screws to my mill as part of a cnc conversion. I have about 0.15mm backlash in both the x and y axis. What would you recommend to remove the remainder of the backlash mechanically? Thanks in advance.

Our MAch3 USB interface boards can be located here:

https://www.buildyourcnc.com/item/electronicsAndMotors-electronic-component-breakout-Mach3-USB-Board

Click the link to add information to this solution:
I am interested in the 3 axis combo USB option. I notice you endorse the Planet-CNC for use with this but will Mach3 interface well with the USB beak out Board?