Control a Relay for a "tool change"

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mrarmyant
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Control a Relay for a "tool change"

Post by mrarmyant » Mon Jul 18, 2016 4:02 am

3D printers support offset heads, and I would love to have a relay (I was going to do this with a switch but a relay controlled by the CNC would be much better) so that PWM output could go to the spindle controller, run the tool, then on the Z axis is also my 7 watt laser that would be a fixed offset from the spindle. Has anyone done this? So a double pole relay that when off runs the spindle, on runs the laser. I don't know enough about GRBL or GCODE to set that up as a tool but it seems like it would be real simple.

Bertus Kruger
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Re: Control a Relay for a "tool change"

Post by Bertus Kruger » Mon Jul 18, 2016 7:24 am

Interesting idea. My concern would be the pin states on startup. Would not want the laser to fire at the wrong time.

You can always use the coolant pin to switch between tools?

Also make sure to use a relay board that is compatable with I/O pins. The pins can only provide around 20ma.

I would suggest having some kind of arming switch on the Laser/spindle power supplies or should I rather say a emergency cut-off switch. :)

mrarmyant
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Re: Control a Relay for a "tool change"

Post by mrarmyant » Tue Jul 19, 2016 1:16 am

They can actually share a power supply the way I have it setup but it would be a double pole relay. Is GRBL capapble of using the coolant pin as knowing there are two onboard tools with offsets? I'm just used to dual head 3d print extruders.

mrarmyant
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Re: Control a Relay for a "tool change"

Post by mrarmyant » Tue Jul 19, 2016 1:17 am

I'm also assuming that since I'm switching where the PWM signal goes with the relay (from the PWM spindle controller to laser driver) that when the spindle driver or laser got no signal it would be in an off state.

Bertus Kruger
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Re: Control a Relay for a "tool change"

Post by Bertus Kruger » Wed Jul 20, 2016 4:34 am

mrarmyant wrote:They can actually share a power supply the way I have it setup but it would be a double pole relay. Is GRBL capapble of using the coolant pin as knowing there are two onboard tools with offsets? I'm just used to dual head 3d print extruders.
I am not totally sure, I know GRBL has offset so changing that with tool changes might do the trick. (Don't quote me though :)

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Re: Control a Relay for a "tool change"

Post by Bertus Kruger » Wed Jul 20, 2016 4:40 am

mrarmyant wrote:I'm also assuming that since I'm switching where the PWM signal goes with the relay (from the PWM spindle controller to laser driver) that when the spindle driver or laser got no signal it would be in an off state.
Yes.... I would suggest a pull-down resistor on both tools(10K to ground on the signal pin ) to ensure they don't float around,activating at unexpected moments.

I would put this on my "To-Test" list just to make sure the spindle/laser drivers are not inverted.

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