Computing stuff tied to the physical world

Laser cutter electronics

In Hardware, Software on Sep 19, 2012 at 00:01

The last part of this mini series about a low-cost semi-DIY laser cutter describes the electronics and firmware:

DSC 3506

In the middle is an MBED microcontroller based on an ARM Cortex M3 chip (NXP’s LPC1768). It runs at 96 MHz, has 512 KB flash, 32 KB RAM, USB, and an Ethernet controller on board (but not the magjack).

The whole thing sits on the custom LaOS board, which includes an SD card socket, an I2C bus, some opto-isolators, power-supply interface (+5V and +24V), and two Pololu stepper drivers (or nearly compatible StepSticks).

There’s room for 1 or 2 more stepper drivers, a CAN bus interface, and more connectors for extra opto-isolated inputs and outputs. The on-board steppers can be omitted with the step/direction pins brought out if you need to drive more powerful motors.

The MBED was briefly mentioned in a previous post, and can also be replaced by a suitably modded LPCXpresso 1769 board, at less than half the price.

The software is open source and has just been moved from the MBED site to GitHub. Note that at this point in time, the software is still based on the “mbed.ar” runtime support library, which is unforunately not open source. Work is in progress to move to a fully open source “stack”, but that’s not the case today – the Ethernet library in particular hasn’t been successfully detached from its MBED context yet.

Ethernet connectivity is based on the lwIP code, which in turn is the big brother of uIP. Big in the sense that this supports a far more capable set of TCP/IP features than would be possible with an 8-bit microcontroller and its limited memory. Having 512 KB flash and 32 KB RAM in this context, means that you don’t have to fight the constraints of the platform and can simply focus on getting all the functionality you want in there.

Right now, the LaOS firmware drives the steppers, using a Gcode interpreter adapted from gbrl, and includes support for Ethernet (TFTP, I believe) and the SD card. It also requires the I2C control panel. As a result, you can send a “job” to this thing via VisiCut, and it’ll save it on the SD card. The I2C-based control panel then lets you pick a job and start it. Quite a good workflow already, although there are still a fair number of rough edges.

(Note that if you listen very carefully, you can hear all the pioneers on this project scream for more volunteers and more help, on all sorts of levels and domains of expertise :)

What excites me about all this, apart from those ├╝ber-cool laser cutting capabilities of course, is the potential to take this further since all the essential bits are now open source – and it’s not even really tied to a specific brand of laser.

So there you have it. It cuts, it burns, it smells, it’s yearning to be taken to the next level :)

  1. Fascinating project, and I would love to help. Unfortunately I doubt I have a required skill. I suspect you’re all very well practised in setting fire to things already!

    The lack of a laser cutter could also be a problem ;-)

    Dear Santa, please order a larger sleigh and add some more reindeer. I’ve got an addition to my wish list – Yes, it’s that JC guy again, he’s been showing me more cool gadgets.

  2. I’m really tempted in buying this laser cutter too, since the price is doable and it would be a nice way to start getting some experience with tools like this.

    Have you knowledge of other sources on the internet with info about laser cutters that are worth looking into?

    If I decide to buy one of those machines I’ll probably try to set up a “group buy” in Belgium (or BE + NL) and drive to the UK myself to fetch it.

    • I think all the low-cost laser cutters end up being derived from just about the same model. For questions, I suggest signing up on the LaOS forum – several people there who have been far longer at it than me!

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