Auto Tool Zero

[nova24]

I'm in the process of getting everything together to setup a auto tool zero routine using Mach3 and a KFlop board.

My router is a Porter Cable 7518 and it doesn't have a ground lug on the plug. I'm not sure if that means all of the electronics inside are fully insulated from the metal body or not. When I dissembled my last PC 7518, I don't remember seeing anything that contacted the metal body.

So, with that being said, would I wire it like this?:

IO34(JP6, Pin 15) on my KFlop would connect to the motor housing, since this input is pulled low.
VDD33 (JP6, pin3) would attach to the touch off plate.

I'm thinking of wiring this way because if the router body is connected to earth ground and I connect the +3.3VDC (VDD33 (JP6, pin3))to the router body, I'm essentially causing a direct short to the negative side of my DC power supply, which is bonded to earth ground.

Thanks,

Dennis

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[nova24]

Since no one has chimed in here yet, I'm going to share what I've found out so far elsewhere. Thanks Erik and TK from the Yahoo forums.

This is not the most desirable way to hook this circuit up, but it will work. I'm quoting the post as it I received it from TK on the Yahoo forum.

---Post start---
KFlop's 3.3V inputs will be damaged if ever driven above 3.9V or below -0.6V. They have ESD protection but there is a limit to what that can protect against. Running an input pin 10ft away and directly connecting it to an exposed plate that then connects to a noisy earth ground is almost asking for trouble. Earth grounds can often have 10V of voltage spikes or more.

If you don't have an opto coupler then as a variation of Ray's method place a resistor in series to the input pin near KFLOP to help protect KFLOP. A 10V spike on the touch plate will then just feed ~10ma into the input and not cause any damage. So for example do:

+ 3.3V
|
|
300 ohm
|
|

-----X------------ 1K ohm ------ > KFLOP Input

|
|
|
| (long wire)
|
|
Touch Plate/GND

---Post end---

This method requires the router body be attached to an earth ground.

The 300 ohm resistor attached between 3.3 VDC and the 1K ohm resistor is used to pull the input high.

The 1K ohm resistor helps protect the input on the KFlop board, as stated in the post above.

As mentioned in the post, an optocoupler is the best/safest way to make this connection. I've ordered the optocouplers, only .25 each, and will post back the information on how I wired them for my system once I get everything working.

Thanks,

Dennis