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GRBL Control Box with Relay Module / Laser

Savvas Papasavva

Project by

Savvas Papasavva
London, UK

General Information

Rebuilding the control box to include relay module and laser driver board.

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GRBL Control Box with Relay Module / CNC Brain - Part 1

120 minutes

00:02 Dismantled original components for X Carve controller taking pictures along the way for your own reference.

00:58 Installed kettle lead panel mount and wired to PSU using crimp terminals. Depending where you buy your panel mount, the wiring may be different.

03:13 Connect 3 cord flex from power in terminal on PSU towards relay module.

04:00 I wired up a gang socket which would pass through the glands on the front panel, and connect to relay. I’ve drilled two as I am using a dual relay module.

04:30 I then connect the 24v power to GRBL shield via E stop. The E-stop is fitted on opposite end of front panel.

05:14 I drilled the holes for all the other front panel connections.

05:20 These include four 4 pin aviation mounts, which need to be soldered to lengths of 4 cord flex which will connect to stepper terminals on shield. (I’ve added two additional opening in anticipation for a laser module.)

06:56 Cut or disconnect original limit switch wires – keeping enough material to make connection within control box.

07:23 Wire ground and spindle enable to switch. If you are not planning to add a laser module you can take these directly towards relay.

08:14 In the video I pushed a tinned red wire into the 5V header but I later soldered this on. I then heat shrinked the wires together, adding DuPont header connections and fitting on relday.

09:31 Solder X, Y, Z and limits to male aviation plugs.

09:58 Add second power panel mount to back panel.

10:10 Testing the controller. Everything seemed to work but the relay was remaining on because the later version of the firmware assumed I was using a variable speed spindle. I had to change something in the config file and flash the shield. This useful blog walked me through the stages:

11:12 I now ran into another problem, as the relay always turned on when the controller was powered. The G code commands were also swapped. This could be quite dangerous, and I couldn’t figure it out so I asked Nathan from OpenTronic to problem solve this for me. He found another command in the Config file that had to be uncommented.

12:08 Now I will show you that it works, using a disco laser.


Installing Laser Driver Board into CNC Controller Box / GRBL - Part 2

00:02 Ok so the next stage of this controller box project or build, is to add one of these step-down voltage regulators to drive the laser driver board.

01:45 Ok so the first thing I’m going to do is wire up the power cable to this step down voltage regulator, and I’m going to wire it up the same way I did the GRBL shield with the option of using a e-stop to cut power to it, and also therefore the driver, the laser driver.

03:03 Ok so I’ll just show you the first part and I’m not going to wire this up yet but this is what it should look like. You have the two terminals that go from the power supply unit into the voltage regulator via what will be the e-stop. And literally connect this way around from there to there.

03:27 The laser originally came with this power supply unit and Big Clive done a review of the power adaptor and it’s pretty scary. I don’t think I’m going to use this with anything ever but what I would like to try and do is utilise the power connection and this half of the cable.

04:55 I am now going to set the voltage output to 12v and I do this by using the voltmeter to give me a reading, and terming one of the pots on the board.

05:46 I’m just soldering the aviation panel mounts now and wiring everything up.

08:03 So I ran into a new problem where the driver board was powering the laser even though the selection switch was set to the middle position. It seemed whatever I had done to compensate for my relay module being of the active low variety was causing another problem with the driver board. Nathan lent me a 10k pull-up resistor and suggested wiring it between the 5v terminal and the single enable pin on the TTL input on the driver board. This seemed to work and produced a valid logic level, whatever that means, but when I plugged the USB cable into the laptop whatever I’d done had reversed and the laser came back on.

09:59 I’m not sure why this is designed the way it is, and if anyone know the correct way of inverting this please do share that information in the comments. I think I am a step closer to the having a controller which can swap between a laser and relay spindle although the real test will when sending a file to the machine.

10:25 I’ll save how I did all of that for another video but I’m just going to show you that it now works.