Category Archives: PCB Fabrication

Pretty on the outside and ugly on the inside prototype

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So I’ve been busy doing a bunch of computer maintenance and looking into other things I’ve neglected while building the roaster so it’s been a bit slow.  I decided I wanted to start gluing corners together and drilling some holes to see how the case goes together so I can eventually get back to fixing the issues with the roast controller case.  Over the past several weeks I soldered together all of the boards, made wiring harnesses and figured out a bunch of “oops” moves I had made designing things when I got rushed for time.

Turns out I was not able to get stand offs locally in the sizes I had wanted so the heights are all screwed up where I placed holes on the outside surfaces.  I also forgot to specifically allocate power for the exhaust fan in the original design BUT I did have “Spare” pins allocated. The fan I ordered also was not the right size for the hole template I had used (Inside fan dimension vs outside screw / case dimension)… neither of them were actually labeled right the way every other fan I have is sized.

So with everything screwed or harnessed in place this is what I have for the Arduino…

The Arduino wired for Coffee Roaster control

It is a MEGA2560 mounted on a Crib for Arduino.  On top is an Ethernet Shield w/ microSD slot.  Then I used a variety of crimped headers to connect to some of the pins on the MEGA and on the ethernet shield.  I have twenty five lines in the bundle going to the Arduino.  I had some spare 10 strand cables from a project at Halloween and no 25 strand cables to use so I used one of those cable wraps to keep the all together after connecting DB25 to one end and header pins to the other.  Once the lid for the crib for Arduino is in place it then connects to the back of the enclosure.

Wiring Harness connecting to the back of the controller enclosure

As you may notice the sockets I was using for connecting the power out are the type that snap in.  The majority of these will not snap into most laser cut plastic sheets and instead are designed for aluminum cases.  The plug to the right on the other hand screws in.  These work great with a variety of thicker locations.  The fan was originally going to be on the inside with a wire cover on the outside but with the wrong size fan hole in use I had the wrong cover to fit the fans that I had that would fit the hole.

For the DB25 connectors it turned out good that I had decided to use a cut out pattern  that had the holes on the side for the anchoring hex nuts rather than just having them cut out so that I could mount them to the socket and anchor the connector.  Since the stand offs were too short they don’t allow me to anchor the PCBs to the bottom plate.  Instead I had to screw them to the back plate using normal screws and with the burnt circles on the laser cut work I had to use some washers too to keep it sturdy.  This is what the back plate looks like.

Rear Panel of controller

This panel includes – One non-filtered switched 15Amp Power Entry module, 2 snap in 15 amp convenience plugs, 1 5VDC fan, 2 DB-25.  The left one is the main guts for the LCD, TRIAC control, potentiometers, thermocouple, and a variety of other sensors.  The right includes all the non-essential stuff for backlighting all the buttons on the button pad and a few other things including spare wiring.  You cna see just a screw on the right since it was relatively intact and so it won’t block the DB25 plug being used.  The right DB25 has washers and screws in place.  These are primarily used to attached the PCB in place attached to the back side.

Next up is the inside view of the electronics area:

Rear View of the Back Panel

Rear view of the back panel.  I need to shrink up the crimp connectors around the wire  (they shrink like heat shrink tubing but is actually much firmer).  Also the connector on the right side (the switched power entry module) should have the screws more securely fastened with nuts and washers but this is mainly just a test to ensure it all fits together and then allow me to focus on some programming for a while to see if I can get more working and develop menus etc.  The clear acrylic bar is used to anchor the corners better.  I need to change the locations of the screws since I could not find screws the size I wanted without spending way too much for large quantities of them on the internet and having them shipped to me etc.  The thermocouple board on the right had the same issue with the stand offs so it is just floating loose in there right now.  I need to find somewhere to get the Omron thermocouple sockets where I dont need to order them by the 1000s since it looks like Ryan McLaughlin has stopped selling things on his site when they (used to) have problems getting the newer MAXIM thermocouple chip.  They’re all over the place now but he hasn’t restarted his store up so I don’t know the deal there.

Here is the view down into the enclosure from above:

Top view into enclosure

With the cover on:

Front panel installed on enclosure

Front panel running

Front Panel Running

When I send it back out again for a new case I hope to have a different board to install that will be switching the smaller breakout boards being designed onto the circuit board as well as add a power supply and possibly having an arduino board mated on top of the circuit board perhaps to bring more of the electronics inside.  I might want to try to get a Digilent board perhaps to try converting to it as a transition between Arduino and PIC32 before I completely switch to a dedicated PIC32.

I’ve also been looking at possibly creating a dedicated PC application to communicate with it directly via USB and over ethernet.  I am toying around with the “QT/QML” language but havent gotten too far with it.  I may just go back to Processing though.

RoastGeek Button Pad v 1.0

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This weekend the final resistor I was waiting for arrived.  As a result I was able to solder the button pad board together and mount all the buttons.  I placed the board on my infrared preheater, applied some solder paste using the syringe dispenser on each of the pads, and then using a pair of Weitus tweezers started placing 0603 resistors from the piece cut from a reel.  I then turned the heater on and let it sit for a bit before turning it up a few more times until I got close to the temperatures I needed.

RoastGeek Button Pad v1.0 on Infrared Pre-Heater with SMD resistors placed.

Without a stencil it’s pretty hard not to goop too much solder paste onto the pads.  In most cases I had a suitable amount but a few it got a bit too much.  For most of the cases I had too much I removed some while it was still liquid-like from the preheater softening the paste.  I used the tweezers with a tiny bit of paper towel to wipe some away on the worst spots.  Solder paste is essentially  a mixture of a type of flux with a fine dust of the solder.  When the temperature gets high enough the flux material starts to liquify and the solder particles flow with the wet flux-like material towards the meeting point of the pads and the item being soldered.  As you apply a final amount of heat the solder particles melt and the flux-like material starts to evaporate/burn up.  To do this I used a hot air rework station to heat up the area near the resistors.  It has a pretty gentle flow that I can adjust with a knob so I didn’t have any issue of the resistors blowing away.  This tends to be a common problem using a hot air rework tool to solder SMD parts.  Once they were all in place I turned down and then a bit later fully off the heaters and allowed it too cool down.

0603 Surface Mount Resistor soldered to the board with an infrared preheater and a hot air rework tool.

Once the surface mount resistors were in place I tested each pad on each side of every resistor and confirmed that the correct resistance was measured.  This was to confirm that I didn’t have any “over gooping” resulting in the resistor being jumped by solder underneath of it.  Everything checked out ok so I continued on to mounting the buttons and header pin connections by hand with a standard iron.

RoastGeek Button Pad v1.0 with buttons, caps, and headers mounted

At this stage I tested the board with an Arduino sketch and was able to measure each button as expected.  This board has a much more accurate number compared to the last board.  Each button previously would measure a number that ranged 3-4 from the highest to lowest reading.  This one is dead on for almost every single button except for 2 of them that vary by 1.

I then mounted the board to the back side of the control panel.  I discovered that the standoffs I am using are about 1-1.5mm too tall so I will need to either grind them down or find a different set of stand offs.  I’m thinking of getting some Nylon or ABS ones that have a self-retaining clip for the circuit board side and a threaded end for accepting a screw from the front panel.  I also need to begin wiring up some wiring harnesses to go between the LEDs and potentiometer over to the new board.

I’ll add a picture of the mounted board  here once that takes place.

First order of circuit boards from OSHPark.com

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If you were following comments in one of the previous blog posts I just received my first order of circuit boards from OSHPark.com. This order included version 1 of my button board and a preliminary interface board to connect a variety of sensors and some of my other boards to an Arduino Mega 2560.

I got to experience the “joy” of being one of the initial test subjects for the brand spanking new OSHPark.com site. It actually worked pretty well and was rather impressive in terms of the graphical response you got from it. It would evaluate the files you uploaded and convert them into a graphical rendering of the finished product. When I ran my boards through the system I did notice that the silkscreen appeared to be NOT the rear/bottom view as the site described but instead it was the “Superman X Ray Vision” view. If you’ve used Eagle and a few other competing PCB CAD programs this is what you normally see when working on your board. Your test will be “reversed” or “mirrored” and the holes will be in the positions they would be in from above. It is thus like you are looking through the layers from above. I mentioned this oddity in my comments on the job but don’t know if they’ve resolved it yet by changing the code or changing the description.

The timeline for my order is as follows:

  • May 21st – Placed Order (T=0)
  • May 25th – Tweet @laen replied by @OSHPark reported that the system is not sending notices yet. Indicates board have been reviewed and panelized. (T+4)
  • May 29th – Received official email that said boards on panel for May 31st.  Notice website reports May 30th as panel date. (T+8)
  • June 7th – Received notice saying boards sent to the fabricator. Probably just an update to the software of the site and the boards were sent prior to this point. (T+17)
  • June 8th – Received notice saying boards received from the fabricator awaiting de-panelization. (T+18)
  • June 15th – Boards apparently processed for postage based on postmark. (T+25)
  • June 18th – Received boards. (T+28)

As mentioned I expect most of the dates to be unreliable other than the fact that it took 28 days start to finish.  The site still has not changed from a status saying my boards are waiting to be de-panelized and nothing about being shipped.  Obviously it is a work in progress.

Here is the collection of boards received

First order from OSHPark.com. My Button Pad board and the preliminary interface board to connect a variety of sensors to the external Arduino mega.

The spacing seems to be exactly what the CAD said it would be and the holes drilled seem to be very accurate and centered like they should be including some of the very small vias.  I will need to crack off and dremel/sand off the rough spots from the edges where the boards were connected together.

More pics:

Interface board

Button Pad 1.0 with several buttons placed

Button Pad v1.0

Button Pad 1.0 Top

Button Pad 1.0 Rear

At this time I am waiting for 330 ohm 0603 resistors to arrive.  They were on back order and should arrive in a few more weeks.  Once they arrive I need to use my infrared preheater to heat up the boards and then do a quick solder on each of the resistors before connecting all the various through hole parts.  Once that happens I’ll update with a new photo showing the finished boards.

Ordered some circuit boards today.

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So I’ve been looking at making a circuit board for some of the roaster project for quite some time.  As the shape/size of the enclosure has started to become real I started trying to figure out what exactly would fit inside the case options.  Some of the items I figured I could prototype/etch myself and others I’d need to send out to get made.

The first board that seemed likely to be something I could make on my own was what I call the “button board”.  It turned out that I decided to send this one off rather than try it myself because I had already made one using Radio Shack parts for an early microswitch version.  The circuit worked great and I happened to be finishing the Laser Cut Roaster Controller case.  The spacing is kind of tight for what I want and rather than trying to drill it manually and the fact that it will ultimately be a pretty permanent part of the project until I switch to version 2 that won’t only use a single analog pin and instead goes entirely digital with a group of pins or I do away with the button pad entirely… so I decided to have it made too.

I wanted it to use 2×5 shrouded pin sockets and some single row pin headers in addition to the MultiMec 3F switches, 1V “Arrow” key caps, some round ones, and some square ones.  I started where I laid out all the buttons and then had some left over pins after allowing for all of the bi color internal lighting LEDs.  I then added some connections for the Fan and the Heat potentiometers that were to the left and right as well as the LEDs on each side.  The wiring harness for each side will had the GND/Voltage and Potentiometer  wires in one bundle and the LED Cathode/Anode wires in the other all connected to a 5 pin connector on their respective sides.

Once I had the design figured out and checked all the spacing and sliced out a paper template with an knife and slid the cover over the buttons and the holes lined up etc I started looking at how much it would cost to get a board made.

One of the first places I looked was BatchPCB.  Once it figured out the whole CAM/Gerber/whatever process and zipped up my files I uploaded the board to the site and a few minutes later it reported it was ready to add to my cart and would cost me $18.83.  I figured I needed at least 2 because I was going to make a second controller at the same time I was making the first one so I always had a “test” one and a “now that I made the first one funky I’m “in the zone” now and can make the second one prettier/better.

So I started thinking I need to double that and maybe a third one wouldn’t be bad since I might use the button pad pattern on this other project I was thinking about.  So two of them is $37.66.  Wow… that’s starting to get kinda spendy for a button pad I’ll probably stop using eventually and need to redo.  PLUS the buttons are horribly expensive too!

I started looking for cheaper options and came across iTeadStudio, SeeedStudio, and DorkbotPDX as some of the more recommended ones.  All would give me 3+ boards and iTeadStudio and SeeedStudio would do around 5 to 10 boards depending on some of the options selected.  A few people reported damaged boards coming back on one of them but usually had replacements to “cover” it but the occasional issues and the frequency of damaged boards showing up seemed a little too weird for me.  Further one of my board has really wide dimensions compared to the height.  This immediately bumped me into a cost structure that made a stack of boards run $70-80+ instead of the 30s.  Additionally since I’m making a prototype that had limited utility and I intend to use hard for a while I figured I’d stick with either BatchPCB or the Dorkbot option since the boards seemed nicer.  For projects that are a little more generic that I could make a lot of a really small boards for mounting certain chips or other devices I’d come back to Seeed or iTead someday.

As mentioned since two boards from BatchPCB cost so much I looked over at Dorkbot PCB Order and realized Laen had launched a new website – OSHPark.com to act as the front end for the PCB ordering.  It automatically reviews the files, renders a bunch of images and then calculates the dimensions and gives you a price and collects money via PayPal or Google Checkout!  One of the big problems with the sites other than BatchPCB was that they all made you email your files to someone who looked them over and then emailed you a price later.  I’m soooo instant gratification when it comes to buying stuff and needing to know the price.  I was VERY tempted to go BatchPCB just to get it in the queue and have a price even if it was high until I saw OSHPark.

When I saw it actually render the images out in such a decent quality and large size it totally stomped BatchPCB.  BatchPCB has HORRIBLE renderings and the price per single board is really pretty awful compared to OSHPark/Laen/Dorkbot.  BatchPCB wants $37.66 for two button boards plus the $10 handling fee per order.  Three of them from OSHPark is $37.70.  So this afternoon at lunch I uploaded my button board AND my interface board.  More on that at the bottom.

Button Board v1.0

RoastGeek Button Pad v1.0 Top

RoastGeek Button Pad v1.0 Bottom

Interface Board v1.0

RoastGeek Interface Board v1.0 Top

RoastGeek Interface Board v1.0 Bottom

As you can see there are numerous connectors on this board.  There are a few resistors and two DB25 connectors.  I’m using the DB25 to connect from the Arduino over to the other boards that will be mounted inside the Roaster Controller Case.  Each one will be attached using a short header pin extension or plugged in directly.  Most of the boards are SparkFun breakouts with a few odd balls.  The connectors marked F_PAD and H_PAD are the ones that go up to the Button Pad V1.0 board and are serviced by that left side DB25.  Most of the other headers and connections go to the other DB25.

The interface board is insanely tight for the routing.  It absolutely will test the software and manufacturing of the manufacturer and will test my selection of screws and stand offs when I try to connect it.  I believe I may have to dig out the plastic stand offs that have “spring clips” instead of screws that I had laying around in storage if it turns out to be too bad.

Like the Laser Cut Case I need to “hurry up and wait” for this one too.  I will be adding comments as I have communication about status and receive the items etc.  I’ve got a LARGE amount of 0603 resistors loaded into a shopping cart at Mouser and DigiKey right now and am trying to figure out the various parts that I need and the back order state/cost/estimated time to ship/etc to decide what I’m going to do.  The biggest problem is finding 330 ohm 0603 resistors.  Apparently nobody sells the damn things in stock.  I have to back order them even though they’ll sell for the same price as the in stock ones in any quantity… they’re just not stocked right now.  I also need to order 2 short 3 foot or so DB 25 cables.