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Grbl PCB complete solution with optocouplers

2 years ago 3133
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To get rid of the many internal wires inside my grbl /driver switch box i decided to develop a complete solution with an arduino nano and optocouplers like shown on I want give the OK's a chance because of bad experiences with alarm triggers due electrical static or magnetism from other machines. Also i plan to make a power distribution board to provide the lower voltages for pi, Arduino, display from the 36V source.

The project is still in development because i plan to mill the pcb and checking if hand or autoroutig makes more sense to get an mill proof output.


grbl ok



ID Name Designator Footprint Quantity
2 OPTO OK1,OK2,OK3 DIP4(opto) 3
3 1k R1,R2,R3 0.25 resistor 3
4 220 R4,R5,R6 0.25 resistor 3
5 5mm ST U2,U3,U4,U8,U9,U10,U11,POWER12V 1x2 5mm Screw Terminals 8
6 WJ2EDGVC-5.08-3P P1,P2,P3 WJ2EDGVC-5.08-3P 3




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Comments (1)

Andrew Gillham Reply

Hello Matt,

Nice project, I was thinking of building something like this.

Just to let you know there is no benefit to using opto-couplers if you connect both sides to the game ground net or pull both sides up to the same voltage rail. Their purpose is to provide isolation between different electrical domains. If you connect both sides together the isolation is broken so you might as well just use a transistor or nothing at all. Also they won't provide the de-bounce, noise immunity or ESD protection you are looking for.

Usually it would be more normal to use opto-couplers on the outputs that go to the motor driver (you would need six of them). Just connect pins 3 and 4 to the output connector, the motor driver will pull the photo-transistor up to it's own voltage rail and when the led is lit it will pull the rail low which enables the driver. For the switch inputs just put a capacitor in parallel with the switch to reduce noise / false triggers (as in the link you provided). You might still have issues with mechanical switches due to vibration.

Best of luck with your projects.


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