LAOS Laser

h1. LAOS Mainboard v05

This page describes which parts you need to build revision 5 of the LAOS mainboard. The revision 5 mainboard is a completely redesigned version of the mainboard. It is still compatible with the older versions but the layout has changed.

The board is designed in KiCad and all design files are available on github: https://github.com/LaosLaser/Hardware/tree/master/laos-board-rev5 .

For a pdf of the schematics see here: https://github.com/LaosLaser/Hardware/blob/master/laos-board-rev5/laos-board.pdf?raw=true

To assemble a Laos mainboard some soldering experience is required. Please read the whole page before ordering parts and assembling.

h2. Choices

Before ordering the parts a few choices have to be made:

- External stepper drivers or Pololu 1182 stepper drivers. If you are going to use external stepper drivers, you can omit the Pololu drivers and their capacitors (100uF: C9, C10, C11)

- Power source for the mBed: if there is a stable 5V power source available in you laser cutter you can omit the 7805 and bridge VCPU to +5V

- Connectors: HPC's lasers use JST connectors, the footprints of the connectors also allow for 5.08mm pitch connectors like a Phoenix contact MSTBA on the PCB and MSTB on the cable.

- 24V transistor output: Q1 and Q2 are two heavy NPN transistors that can be used to switch external loads. If you don't want to do that you can omit J27, Q1, Q2, R17 and R15.

- SD card or microSD card: since revision 5 there is an option to mount a microSD card holder instead of the full size SD card holder. Where the regular SD card sticks out of the board, the microSD card stays inside the board. The microSD card holder is harder to mount and some microSD cards may not work with the board (SPI support is not mandatory for microSD cards). When in doubt: use the regular one.

Some parts are not (yet) supported in the software and are therefore not neccesary:

- USB connector (J1)

- CAN bus (CAN1, R1, U1, C2)

h2. Buying parts

You will need at least these parts:

|*Amount*|*References*|*Value*|*Function*|*Part*|*Farnell*|*Farnell price*|*RS*|*RS Price*|

|1||||Laos mainboard|||||

|5|C1, C2, C3, C5, C8|100nF|Decoupling capacitors for diverse parts|100nF Ceramic capacitor, 5.08mm pin spacing|2112751||721-5240|€ 0,07|

|1|C7|22nF|Input decoupling for the 7805|22nF ceramic capacitor, 100nF is fine too|1141773||721-5268|€ 0,12|

|1|C4|1000uF|Voltage buffer for the Pololu's, stabilization of Vmot|1000uF capacitor, 5.0mm pin spacing, 10mm diameter; voltage rating at least 1.6 to 2 times VMOT|1855170 (moq 5)|€ 0,65|520-1090|€ 1,31|

|1|C6|100uF|Voltage buffer for VCPU.|100uF capacitor, voltage rating at least 1.6 to 2 times VMOT|1902932||520-0996|€ 0,28|

|5|R10, R18, R19, R21, R22|10k|Pullup resistors for the optocoupler inputs and analog input|10 kOhm resistor|9339060||707-7745|€ 0,02|

|13|R12, R15, R17, R30, R2, R3, R4, R5, R23, R24, R26, R27, R33|1k|Diverse functions: current limiting resistors for the leds, bias resistors for the high current output transistors, voltage divider for the analog input|1kOhm resistor|9339051||707-7666|€ 0,02|

|4|R28, R29, R31, R32|330R|Current limiting resistors for the leds in the output optocouplers|330 Ohm resistor|9339418||707-7622|€ 0,02|

|1|R34|100R|Limiting/protection resistor for the microcontroller's analog input|100 Ohm resistor|9339043||707-7587|€ 0,02|

|2|R7, R8|2K2|Pullup resistors for the I2C bus|2.2kOhm resistor|9339302||707-7690|€ 0,02|

|1|J11|MBED NXP|The microcontroller that's the core of the board|mBed LPC1768 module|1761179|€ 49,73|703-9238|€ 49,53|

|1|J4|MAGJACK|Ethernet connector with magnetics|MAGJACK SI-60002-F|1137981|€ 6,27|741-8477|€ 4,38|

|1|U2|Hirose DM1B-DSF-PEJ(82) or Molex 502774-0891|SD card holder|Micro SD SMD: Molex 502774-0891 Regular: Hirose DM1B-DSF-PEJ(82)|9688862|€ 2,65|685-0788|€ 2,22|

|1|D1|LEDR|This led indicates that the stepper drivers are enabled.|Low cost 3mm red led|1045372||708-2753 |€ 0,09|

|1|D2|LEDY|This led indicates the presence of VMOT|Low cost 3mm yellow led|2080002||708-2769 |€ 0,11|

|1|D3|LEDG|This led indicates the presence of a 5V supply for the microcontroller|Low cost 3mm green led|1652494||708-2756 |€ 0,11|

|2|IC1, IC2|KB847|Quadruple optocoupler for the endstops/outputs|Kingbright KB847|2001656|€ 2,04|619-2026||

|2|||Socket for optocouplers, 0.3inch wide, 16 pin||1077315|€ 2,17|402-771 |€ 0,18|

h2. Connectors

Both 2.54mm pitch connectors and 5.08mm pitch connectors fit in the board. The reference design uses Phoenix MSTBA and MSTB connectors, which are compatible with the sometimes cheaper Wurth elektronik series 351 and 313. The HPC LS3020 (pro) uses low cost JST connectors and a flatcable. The choice is yours, if you want to keep the original connectors you can use the JST connectors, if you want stronger and more solid connectors you can use the larger ones.

h3. Phoenix/Wurth

|_.Count|_.Component|_.RS Part No.|_.RS Price|_.Farnell Part No.|_.Comment|

|1|Phoenix 3-pin Terminal block MSTB 2.5/ 3-ST-5.08|189-6026|€ 2,27|3705365|€ 2,45|

|1|Phoenix 3-pin PCB header MSTBA 2.5/ 3-ST-5.08|189-6111|€ 0.84|3705183|€ 0,88|

|7|Phoenix 4-pin terminal block|189-6032|€ 3,05|3705377| |

|7|Phoenix 4-pin PCB header|189-6127|€ 1,04|3705195| |

|3|Phoenix 5-pin terminal block|189-6048|€ 4,00|3705389| |

|3|Phoenix 5-pin PCB header|189-6133|€ 1,45|3705201| |

h2. Building the board

Collect all the parts, put on your favorite music and heat up your soldering iron.

First solder the SD-card connector; it's recommended to use a fine tip for the small legs of the connector.

<picture>

It's usually the easiest to solder the low parts first; in this way when you put the part in the board and flip it over the part will stay in the board because it lies directly on the table. If other parts were higher the part would fall out.

The lowest part here are the resistors, followed by the leds, ceramic capacitors, jumpers, connectors, electrolytic capacitors and finally the 7805 and large transistors.

<pictures>

h2. Configuring the jumpers

* J28: Vout for the high current outputs

* J43: Endstops

* J40: VMOT/VCPU bridge

* J12, J19, J25: microstepping

* J3: CPU power from USB

* J41: O1 Source

* J42: O2 source

h2. Testing

h2. Connecting your lasercutter

* PWM (capacitor)