LAOS Laser

The past week has seen more progress than the last 7 months.

Last week I moved my laser tube from the worn out unit into the demo unit (without a tube) and hooked it up with water (for the first time) and cleaned the optics, wirh a quick alignment and test fired it at bits of perspex and wood. Lots of fun, need to get the extractor and smoke blower sorted out and make a plan for an adjustable Z-table and perhaps a pin bed. The existing controller homed both axis neatly so the switches and motors should be ready for me when I hook up the LAOS board. I have to locate some suitable connectors as the laser does not use JST or Molex ones. I put Molex pins on the board and will reterminate the cables soon.

The test firmware worked OK and what tests (buttons and inputs) I could do worked correctly, I have not got debug communications working yet but have discussed it in another thread.

I have not figured out exactly when one would use the J44. There is a jumper J3 on the rev.3 circuit diagram, not sure if this is the same thing and not sure if it is needed or not. Could this affect the USB serial port emulation somehow?

All voltages are correct (I had to read the wiki to realise I needed to bridge out the 7805 regulator pads to bring the 5V from the 3-pin laser power connector to the other side of the board). On looking at the circuit diagram I also noticed that I did need to connect the jumper for the VSensor (there are two independent ones with the same label)limit switch inputs (I used 5V) to power the opto-isolators even if I was just planning on using switches that did not need sensor power on the connector.

The electrical design would love to have a set of 3, 4 or 5 voltage signals defined that make sense and are used consistently on all the schematics, the silkscreen and instructions. I have 3 suggested naming conventions that could work. Use Va, Vb, Vc, Vd, Ve and then have a description somewhere that explains the usage of each power rail. Alternately use V24, V12, V5a, V5b, V3.3 to designate the nominal voltages and have the user infer the source and function of each of the rails. The last option is to select nice mnemonics to help identify each power rail and let the user guess as to the voltage to be found on each rail, such as vMOTOR, vCPU, vI2C, vIN-OPTO, vIO-ANA, vCONTROLLER, vOUT-OC and vCAN or whatever. Right now there is a combination of all three naming conventions and no documented reasoning for how they are used besides the connections required for the two most popular standard use cases. If the schematic matched the PCB I could try and make corrections to the wiki descriptions but not fully sure myself what is intended. I must say there is a lot of flexibility but not all options are clear. I also understand that there is some issues with kicad that makes relabelling the nets difficult but at least a description of what each one means would be handy.

Having a list of jumpers somewhere with use and function would be helpful.
Changing the labelling convention between the jumpers/headers and connectors/terminals would make the schematic and PCB labelling much easier to follow.

The microscopic 3V regulator could perhaps be replaced with a TO-92 through hole device for those assembling the board at home, there is a part in that style but it only supplies 100mA so not sure if that is enough for the MBED clone. LP2950-33.

I'm not trying to make work for me or anyone else but good documents make for better uptake and sales and community and growth and such. I try to promote LAOS wherever I go because it looks like a neat open system that has gone together without any real glitches so far. I will make some more edits to the wiki when I have completed the next stage of my adventure.

Regards

Kalle
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Johannesburg, South Africa