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Category — Making an Interface PCB

Making a Single Prototype PCB

I recommend Sierra Proto Express for making automation PCBs.  So far, I’ve had five different boards made at Sierra, including a larger 4 layer board, and have been very happy with the results.  Their pricing is competitive, the quality is excellent, and there are fewer limitations (e.g. drill sizes, non-plated holes) than many of their competitors.

However, when I am paying the bill, Sierra is not a good choice when I only want 1 board made or have a small board.  At Sierra, 1 PCB might cost about $85, and 3 PCBs about $110.  For small quantities, the cost does not vary much with board size (for example, a 6 sq in board costs the same as a 18 sq in board).

I haven’t found a great solution yet. I want all my boards to have top and bottom soldermasks and a top silkscreen, so “bare bones” boards (no soldermask or silkscreen) isn’t an option.  Besides, I don’t think the bare bones savings are large enough.

I do plan on making multiples of some personal boards (mainly some CANOpen-related boards), but for some boards, such as the FP-SMC-1, I only want one board (unless, of course, I can get multiple quality boards done for the same price as the cheapest price for one quality board).

The best solution so far is Batch PCB, which is run by SparkFun; the PCBs are made in China by Gold Phoenix.  Batch PCB charges $2.50 per square inch plus $10 for 2 layer PCBs; typically delivery is supposed to be 2-3 weeks (longer than I  like, but I can live with it for my personal boards).  The FP-SMC-1 PCB would cost about $40 at Batch ((4.32 * 2.83 * 2.50) + 10 = 40.56).

Another choice would be to use Gold Phoenix directly and panelize (combine multiple boards into one order).  Gold Phoenix only makes sense for orders of 155 sq in or more.  They will panelize for an extra fee ($30 IIRC).  So I am going to finish up some other PCBs first, then decide how to get all the boards made.  Given the boards’ design specifics, it may not make sense to panelize, but at least I want to check and see if this is a better option.

March 18, 2009   No Comments

FP-SMC-1 PCB Layout Is Done

3D Model Top View

3D Model Top View

It’s designed!  After taking way too much time, I have finally finished the layout for my FP-SMC-1 board.  Here’s the proof: above is a 3-D model of the board; below are pictures of the layout and the board model from the bottom.

PCB Layout

PCB Layout

PCB Bottom View

PCB Bottom View

The board hasn’t been built yet, because I wanted to model it first, and I haven’t found a good place to get one-off prototype PCBs made.

Creating the board model was challenging, but worth it, because it gives me more confidence that my board layout is correct.  I use the 3-D model to check:

  1. That my PCB footprints are correct.  Look at the picture of the board bottom, and notice how all the pins line up with the holes.  (This check relies on correct 3-D models from the manufacturer.  If you create 3-D models yourself, it’s possible for you to make a mistake in the model, but the manufacturer’s models should be correct).
  2. That my board dimensions are correct and the PCB will fit into the holder.
  3. That my component layout makes sense.  Look at the far left of the board top view picture, and notice that there is clearance between the connectors and the little plastic tabs on the PCB holder that stick out into the board area.

I will go over making the model in detail later, but what I did was roughly:

  1. In Eagle PCB board layout, turn on only the dimension, via, and pad layers (layers 17, 18, and 20)
  2. In Eagle PCB board layout, use a ULP to create DXF of the pads, vias, and dimensions.
    1. Eagle includes DXF.ULP to create DXFs.  However, this file does not produce DXFs that can be used to extrude a through-hole board.  To get DXFs that CoCreate can extrude, I had to modify DXF.ULP and then delete and re-create the board outline using DoubleCAD.
  3. Import the DXF file into CoCreate and extrude it to 0.062″.
  4. Import models of all the components (fortuneately, all the parts have STEP models available from the manufacturer).
  5. Assemble (using mates) all the components onto the PCB
  6. Assemble the PCB holder
  7. Mate the PCB to the PCB holder.

It sounds so easy, but mechanical CAD software has a high learning curve, just like PCB software.  However, if you’re a software guy, don’t be scared — I’m primarily a software guy, and if I can figure out how to make a PCB and then model it, then you can too.

I was originally planning on doing a series of blog posts on the FP-SMC-1 PCB covering just the automation-related aspects of the project, and not covering the details of using the tools (such as Eagle PCB).  However, after I looked at various Eagle PCB tutorials, I decided that none of them explained Eagle the way I think it should be explained.  I did not find any tutorials on making mechanical 3-D models.

So I have decided to write up a lengthy tutorial on how to design and make the FP-SMC-1 board.  The tutorial will be on my Trac site, since I think Trac is better suited for a lengthy tutorial, but I will blog here about my progess (hint: don’t expect the tutorial to be done quickly).

March 18, 2009   3 Comments

All I need is the board

FP-SMC-1 Parts

I have all the parts for the FP-SMC-1 board project except for the PCB. I’ve done a rough hand-sketched schematic; the next step is to create an Eagle PCB library with all the schematic symbols needed.

Tony

May 23, 2008   No Comments

Making an Interface PCB II – Parts and Resources

Updated 1/23/2008 with AMP socket connector part numbers (which some people find easier to hand assemble than 3M, but they are more expensive), and a bit more on MCAD.

Update 4/6/2011: Alibre Design Express hasn’t been available for years, and since Alibre Design Personal Edition isn’t suitable for PCB modeling, your low cost (<$500) MCAD options are limited.  Check out my Affordable MCAD post for some current choices that might work (depending on your needs).

A list of the parts and resources needed for the FP-SMC-1 Interface PCB. The Phoenix parts are available from a number of sources, including Digikey, but Mouser (who I will use) and Online Components sell them in small quantities.

Software:

  1. Eagle PCB. I’ll be using the Light version (free for non-commercial, $49 for commercial).
  2. Viewmate from PentaLogix, which is a free Gerber viewer.
  3. Alibre Design Xpress which will help check the mechanical side of the PCB (free). If time allows, I’ll cover other options for checking the mechanical fit of the PCB.

Board Houses:

  1. Sierra Proto Express
  2. Possibly SparkFun/BatchPCB (can be cheaper for 1 PCB)

Bill of Material for circuit board (excluding PCB):

  1. 4 Pin Header 10 pin (2×5) AMP 5102321-1
  2. 1 Pin Header 26 pin (2×13) AMP 5102321-6
  3. 15 Phoenix ZFK3DS 1,5-5,08 Terminal Block (Part Number 1704415)
  4. 1 Phoenix ZFK3DSA 1,5-6,08 (click on Additional Products) End Terminal Block (Part Number 1704554)
  5. 3 Phoenix ZFKDS 1,5-W-5,08 Terminal Block (Part Number 1706714)
  6. 1 Phoenix ZFKDSA 1,5-W-7,62 (click on Additional Products) End Terminal Block (Part Number 1706730)
  7. 2 Phoenix UMK-FE DIN rail feet (Part Number 2970031)
  8. 2 Phoenix UMK-SE 11,25 side elements (Part Number 2970002)
  9. 2 Phoenix UMK-BE 45 base (Part Number 2970015)

Bill of Material for cables:

  1. 8 IDC Socket Connectors 10 pin (2×5) 3M 89110-0101 or AMP 1658621-1
  2. 8 Strain Reliefs 3M 3448-89110 or AMP 499252-5
  3. 2 IDC Socket Connectors 26 pin (2×13) 3M 89126-0101 or AMP 1658621-6
  4. 2 Strain Reliefs 3M 3448-89126 or AMP 499252-3
  5. Ribbon cable 26 conductor AWG 26/28 0.050″ pitch (available from 3M and others, length depending on your need)
  6. Ribbon cable 10 conductor AWG 26/28 (available from 3M and others, length depending on your need)

Tony

July 26, 2007   1 Comment

Making An Interface PCB I – Introduction

This series describes how to have a PCB made for factory equipment from start to finish using a real board. I am not going to concentrate on the details of the PCB layout software (there are plenty of tutorials available for that), but instead cover details such as getting the right output out of the PCB layout software.

I am going to design a PCB that could be useful in a machine, using components I like. You should be able to learn from this example to design your own low cost board. The PCB will be designed to interface a Panasonic FP0 or FP Sigma PLC to a SMC pneumatic manifold. I am naming the board FP-SMC-1.
The board interfaces 16 PLC outputs to a SMC 26-pin header manifold. SMC uses this design on various manifolds that can have up to 12 stations, and each station can use 1 (for single acting) or 2 (for double acting) outputs. In my board, I use up to 8 stations; all of them can be single or double acting.

The board interfaces 16 PLC inputs to terminal blocks, so you can have two limit sensors (extended, retracted) for each pneumatic cylinder.

The board has a four power terminals, two +24V and two GND. Providing extra 24V and Ground connections allows the board to power another board.

The board mounts on a Phoenix UMK DIN-rail holder. I have successfully used the UMK series before. Phoenix also provides 3-D models, which is useful.

I will be using Eagle PCB to create the schematic and layout the PCB. I will be using Sierra Proto Express as the board house. I plan on investigating the creation of a 3-D board model.

Tony

July 9, 2007   No Comments