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Limit Switch Ground and shared wires

Limit Switch Ground and shared wires
September 19, 2018 10:31AM
I'm building a RAMPS-based XY plotter and have had good success, but I need help consolidating my wiring to add limit switches. I think I have "almost" a good idea for implementing limit switches and 2 servos.
Using Cat5 cable (8 wires, 22 gage) I need one more wire... tell me if this might work or if I'm just going to have to find a 9th wire:
1) X- (Using NC 2-wire limit switches for #1 - #4)
2) X+
3) Y-
4) Y+
5) Servo 1 Signal (D11)
6) Servo 2 Signal (D6)
7) Servo ground - I have added a 5VDC supply at GND & VCC pins just left of reset switch per other RAMPS servo references.
8) Servo +5Volts - VCC

So the 9th wire I need would be the limit switch ground. Is it possible that the servo wire ground (#7 above) is shared/shareable with the limit switch ground?

I see the 2 sided PCB image elsewhere on this forum, and it looks to me like the limit switch negative trace is tied to the board's ground, but I'm not sure -- and I have smoked two Arduinos lately! It's quite possible I have a short elsewhere in my pinout wiring, but at this point, I thought it would be good to back up and question my assumptions. Voltmeter shows pretty low resistance ( a few ohms)... I'd appreciate the wisdom of others who may have gone before me.
Re: Limit Switch Ground and shared wires
September 20, 2018 01:00AM
The servos will draw a lot of current, especially digital servos. I'm not sure, if the 22guage is even capable of driving one servo...
If you can, measure the voltage drop acoss the GND wire. If it's to big, it might trigger endstop pins unvoluntary when their GND is connected.
Or they don't trigger at all, when configured 'active low'.
Re: Limit Switch Ground and shared wires
September 20, 2018 12:17PM
Good thoughts! The current draw for my servos are 180mA and 150mA at no load, 880mA and 450mA at stall. And I've got these things on a very light load, so call it under an amp. The 22 Gauge wires of a Cat5 or Cat6 wire are rated for up to 2 amps. In fact, on a separate Cat5 cable from these switches & servos, I'm powering two 1.5Amp stepper motors with no issues at all (another 8 wires with 4 per stepper).
Retracing my own wires, I did find an unintended ground, so that *might* have solved it. But I'm proceeding cautiously.
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