Electronics design & production

1. Electronics design

V0.2 is based on V0.1 with added battery support. The motor driver microstep pins are fixed to HIGH, and the PCB is now double-sided, making it almost half the size.

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Fusion Electronics (Eagle) library

• RPI-Pico-Eagle-lib
• Eagle-Library-Pololu (Unofficial)

How to use libraries:

1. Download .lbr and upload it into Fusion's Team Hub

2. Open Library manager > Hub libraries > Sync libraries > Add selected Hub libraries

   

3. Place components

   • LDO (3.3V800mA NJM2845DL1-33): Symbol and footprint are equivalent to the one in LDO library
     • Footprint: TO-252-3 (NJM2845DL1)
     • Fusion library: LDO > MC78M05BDTRKG
       • Footprint: 5-SOT23
   • 2.1mm DC juck:
     • Fusion library: DC Power Jacks > 694106105102
   • SBR diode (SBR15U30SP5)
     • Footprint: POWERDI5

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Custom library

For some parts, no public libraries are available, so a simple library can be created. In this case, those are only used for pad and through-hole placement.

Ref:

• FabLab Kannai | Create libraries
• Create your own electronics parts in Autodesk Fusion

Custom components

*In this case they were only used to place pads and holes, without attaching any 3D components.

1. • This library is only used to place 4 through-holes (Planning to use leads (e.g., resistor) for soldering and place insulation spacers)
   • The module can be placed underneath the PCB, saving space and making soldering easier: Swap left and right on the PCB later

   LM2596 module

   SymbolFootprint

   

   • Pins: +IN, -IN, +OUT, -OUT
   • Modified based on the existing symbol

   

   • Footprint based on the LM2596 module dimensions
   • Set "Grid Size" each time to ensure accurate dimensions

2. Mini blade fuse holder

   • This fuse holder is THT and has four through-hole slots.
   SymbolFootprint

   

   • Used the existing fuse symbol

   

   • PTH Pad was set as 0.8mm Long

3. TVS diode (SMBJ45CA)

   SymbolFootprint

   

   • Bidirectional (no polarity): symmetrical symbol

   

   • Based on the dimensions

4. SBR diode (SBR15U30SP5)

   SymbolFootprint

   

   • Modified based on TVS diode symbol as Schottky diode

   

   • The bottom left and right pins (anode) are connected

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Double-sided PCB design

Hole / Drill / NPTH in Fusion Electronics:

Item	Purpose	Electrical Connection	Plating	Notes
Hole (Non-plated through hole, NPTH)	Mechanical holes (screws, alignment)	No	No	Purely mechanical hole
Drill	Hole size definition	—	—	Diameter setting, not an object
Via	Layer-to-layer electrical connection	Yes	Yes	Used for signals or GND

• While routing, press Spacebar to place a Via that connect top and bottom layers
• Then, the route automatically switch to the opposite layer and turn the color (red or blue)

PCB via and rivets

• Via: a small hole that electrically connects copper traces between PCB layers
• PCB rivets: Hollow copper sleeves used as a simple DIY way to make vias on double-sided boards to provide a top–bottom connection
• Typical size: 0.6mm and 1.0mm
• Typical drill sizes: ~0.8–0.9 mm for 0.6 rivets, ~1.5 mm for 1.0mm ones
• Rivets must still be soldered after flaring to ensure electrical connection

Alternatives:

• Wire vias (soldered wires through holes)
• Manufacturer-plated vias

Ref: PCB rivets

Note

The 0.6 mm or 1.0 mm rivets were difficult to find, only the 0.9mm ones were available.

• 0.9mm copper rivets
• It seems like drill size should be 1.3 to 1.5 times larger: 1.35 mm holes

Double-sided PCB mill files

I tried using Gerber2Png from FabLab Kerala to generate PNGs for a double-sided PCB following the Documentation.

In this process, "alignment cut" is used to align the board to the rest of the copper plate when flipping. It offsets the diameter of the end mill on each side so the boards will fit when flipped over.

• Fusion360: MANUFACTURE > Export Gerber

• Gerber2Png:

  • Select all .gbr files (after unzipping)
  • Set Double sided and Generate All > Generate PNG
  • Download PNGs

  

Outcome:

• It successfully generated "Alignment cut"
• The PCB successfully fit in 100 x 70 mm copper board with the alignment cut (95.2 x 63.2 mm)
• Somehow, it doesn't generate PNG for the drill
  • Ref: Kannai's steps (8.4. Export millholes.png)
  • As a workaround, exported the mill holes with board outline as a vector file from Fusion360: Selected DOCUMENT > Print > Print to File (PDF)
  • Opened the PNG and PDF files in Affinity (vector software) and aligned them.
  • Exported the mill holes as a PNG file the same size as the other PNG files.

1. Top Traces2. Top Drills3. Alignment cut4. Bottom traces5. Board outline

Other notes

• Breakout boards such as Pico and A4988 carriers are placed there only for pinout verification purposes and are not required for PCB design.
• Remove them afterwards to avoid unnecessary DRC violations due to THT pins such as routing between pin sockets.

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2. Electronics production

I prepared .nc files using the mods as before.

Milling steps for double-sided PCB

1. Attach the copper plate and attach a V-bit end mill
2. Mill the top traces
3. Change the end mill to a 0.7mm and drill the top drills

4. Mill the alignment cut

   

5. Flip the board over and fit it into the remaining part of the copper plate

   • It was a little difficult to remove the board from the double sided tape while keeping the rest of the part attached.
   • Also applied double-sided tape on the top side.
   • The board fits into the remaining copper plate

   

6. Change the end mill to a V-bit and mill the bottom traces and logo

7. Change the end mill to a 0.7mm and mill the final board outline

   

Resume job at line (gSender)

It went perfectly except for the first top trace, where the plate was slightly tilted and not deep enough on the right side. Using a feature in gSender, I was able to pause the job, recalibrate the Z0 and resume the process right before the issue.

• Press the small list icon on the Start Job button

  

• Enter the line before the problem occurs

  

Copper board material: FR1 or FR4

There are several types of copper plate material, mainly FR1 and FR4. I accidentally picked FR4, and although there seems to be no problem with the board itself, I should have chosen FR1 because of concerns about dust safety and the possibility of the end mill wearing out faster.

Aspect	FR1	FR4
Base material	Paper + phenolic resin	Glass fiber + epoxy
Mechanical strength	Low, brittle	High, robust
Heat resistance	Low	High
Cost	Low	Higher
Safety (dust)	No fiberglass; safer to mill, basic dust extraction needed	Fiberglass dust; hazardous, strong extraction required
Tool wear	Low abrasion, long tool life	Highly abrasive, rapid tool wear

Ref: BANTAN TOOLS | FR-1 (PCB Blanks)

Soldering

Soldering order

1. Rivets

   I used M0.9, 2.5 mm PCB rivets and flattened them with a precision screwdriver due to the lack of a proper punch. It wasn’t ideal, but it worked.

   Rivet topRivet bottomRivet soldered

   

   

   

2. Capacitors and resistors

3. Pin-headers and pin-sockets
4. Bulk capacitors

5. Buck converter on the bottom

   I mounted the LM2596 module with 4 pin-headers, ensuring the two right-side pins were soldered on both sides.

   SolderedWith componentsBottom

   

   I have to admit that my soldering skills haven't improved much...

   

   but it looks okay...

   

   The output current of the LM2596 module was set to 5V using the potentiometer.