I need to connect axis limit switches to the TinyG 8.0 board. There are three terminal blocks on one side of the board near the reset button. It looks like the limit switches for X min/max and Y min/max are wired to the middle terminal block and for Z min/max to the terminal block on the end. I assume, but want to be clear, that a 3.3V source is connected to the terminals labeled GND and 3.3v? A separate power source from the board main power? Please advise.
Connecting limit switches to TinyG V 8.0
From the original Synthetos forum (2011–2025)
3.3V and Gnd are the on-board levels
Each [XYZA] pin is pulled high by 2.7Kohms and bypassed to gnd with 0.22uF.
See for yourself:(sheet 1
https://github.com/synthetos/TinyG/tree/master/hardware/v8schematics/v8h
I don't know what pulled high means. I know what ohms are and that uF refers to capacitance but my knowledge of electronics is limited to that of a hobbyist so I need very simple explanations. I just simply want to know how to connect XYZ micro limit switches to my TinyG board so the axis travel doesn't exceed the mechanical limits of the machine.
High = 3.3V
Low = GND
One SW Term to Xmin
One SW term to GND
Repeat for Xmax
Repeat for Y and Z , min and max
Set Switch type to NC
Choose Switch function as Limit, Home, or Limit & Home
Ok that's what I thought but just wanted to be sure. I'll need to make a common ground strip for 5 micro switches. And I assume that I will need to use a stand alone 3.3v power source connecting the pos to the 3.3V board terminal and the neg to common ground?
No, the 3.3V pin on the connector is there as a reference voltage, an output.
For simply connecting Limit switches, no connection to the stand alone 3.3v pin is required.
That is correct. Wire the limit switches between the ground and the switch inout - e.g. Xmin, Xmax, Ymin...
Note if the switch is Normally Open (NO) or Normally Closed (NC) and set the $st setting for the proper switch type. All switches must be the same type. We recommend NC switches as they provide better noise immunity from false triggers.
You will want to pay attention to switch wiring, as the wiring can pick up noise and fire if not done well. The RC circuits described above help a lot, but motor or spindle noise can creep in. The best strategy is to use twisted pair shielded cable. I have found guitar pickup cable to work well as it is all that plus it's very small and flexible.
These pages provide some useful information:
https://github.com/synthetos/TinyG/wiki/Homing-and-Limits-Description-and-Operation
https://github.com/synthetos/TinyG/wiki/Homing-and-Limits-Setup-and-Troubleshooting
That's good to know. Thanks telling me that.
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