Feb 17: electronics production

Week Four

Assignment

Group Assignment:

• characterize the design rules for your PCB production process

Individual Assignment:

• make an in-circuit programmer by milling and stuffing the PCB, test it
• then optionally try other PCB processes

Group Assignment Page

Link to Electronics Production Group Page

Electronics

MODS

Link to mods website

I followed Brians 'Building the FabTinyISP' website.

• the very first thing I did was printing out the png of my board so that I could double check all the pieces where going to fit into the board. This really helped so that I wouldn't have to make a whole board and then realise its the complelety wrong size.
• x2 .pngs - - > outline of board - - > traces
• the black of the board will be cut away
• Mods = CAM software --> run in a web brower using Javascripts to do the job.

PNGs Traces and Outline Cutout

Before anything I started by getting the PNG files ready, the black lines will be cut away and the white will be kept. The first file of all the lines are the traces that will the copper lines to attch the electronics. The other is the cutout line for the board.

I checked the png of the two png files to makesure they were the correct size which was told on Brians website. To do this you go into 'Tools --> Adjust Size...' this will take you do the page where you can check the 'Resolution'. Check that the drop down is in 'pixels/inches' or 'pixels/cm' as this will change the outcome of the png.

Download the PNG files here:

• Traces - 1000 dpi
• Outline Cutout - 1000 dpi

Mods Program

To open up mods which is a web interface, you have to follow a few steps to get to the correct area for your machine. It tells you on the screen what to do, but you start by right clicking and then it come sup with different options. Follow the steps below to get to the 'roland srm-20 PCB' webpage.

This is the webpage for mods which I used to cut my board out. I have made a list of the stages you shuold take to get to the end outcome, to the right handside of this page there is also more information about what is happening behind mods to get the correct files so that this peice can be cut out correctly.

Be aware that these stages are for both the traces and the outline, you have to make two different files for these two cuts. - - - Follow 2a for traces cutting and 2b for outline cutting.

mods step by step

1. Open up your png file in the web browser by clicking on 'select png file', if you have gotten the colours the wrong way around you can change this here by pressing 'invert'. You also need to check the size of your piece and the dpi which you should know as we checked it before coming into this website.
2. a) You do this first - 'mill traces 1/64' this is a premade setting for the cutout of the traces on your board. 1/64 is a 0.4 mm milling bit, in the next area it changed this to mm so you can check it. b) Once you have done the traces you do this - 'mill outlines 1/32' this is the premade setting for the outline cutout of your board. 1.32 is about 0.8 mm milling bit, the next area is done in mm so you can check it there
3. Here you are checking the all the parts are correct so the 'tool diamiter' 'cut depth' and 'max cut depth'. remember these will be different on the outline and the traces when you set them up.
4. 'offset number' this is the amount of times the tool will go around the edge taking away copper. If you set it to 0 this will take away all of the copper so you are left just with your traces ont he board. - - 'offset stepover' this is the overlap of the tool going over the previous path, if you think about it like it is mowing the grass and goes over the previous section so there is nothing left over.
5. You can now press 'calculate' this will show you in the viewer below what your board is going to look like when cut. You can view this is a seperate tab by pressing the 'view' button. Just makesure you wait for it to finishing calculating before pressing view.
6. This is where it is your preference and you can decide where to place your origin. As default it is set up as 10 for all the x y z axis but I change it to 0 as this make more sense for me now, maybe if in the future I was making many board giving them all an origin of 10 would prevent them from overlapping.
7. Now you need to save what you have just done, to do this you need to connect the output on the 'Roland SRM-20 milling machine' section to the input on the 'save file' section. Now press 'calculate' and this should automatically project a file of your work - be pacient it will save the file when it has completed the calculation. This turn it into an rml file which is just for roland machines and now you are ready to move to the milling machine.

This is a zoomed image of setting the origins to 0 to show you the numbers but also the 'jog height' this is the height of the tool when it is moving around the material when cutting. This must be over 0 otherwise it will scatch the bed material and damage the tool bit.

Milling

Setting up PCB copper board

To start with you choose the board you are wanting to cut, you then place some double sided tape to the back of the board WARNING do not follow me here as this didn't work for my printing and I made my tape go the other way the second time. It will make more sense later on this page when I start milling the board.

You then need to then peel off the tape backing and press down into the sacrificial board, both these items need to be very flat as this will determain the final outcome of your print. I madesure there was no bubbles in the tape and then when I pressed it down I made sure it was as flat as it could be by placing a flat board over it to check there was no gapping.

Setting up the tool

Placing the tool into the machine you have to be very careful not to hit the bit end on the edge of anything or drop it as they are so delicate they can break very easily. Then you must be sure not to over tighten the grubscrew which is on the chuck where you place the tool bit in. By using the allen key (as shown in image) you then can't put too much pressure onto it as it is so long so you wont break the thread but just be aware that this is something you should be careful of but do be sure to tighten it enough otherwise they can fall out... stay tuned.

I used a 0.4 mm square ended milling bit for cutting out the trace and a 0.8 mm square ended milling bit for cutting out the main edge.

Setting up v-panel

Overal look at the v-panel

• The right hand image in that box are the numbers of the origin of the x, y and z of the machine. You have to set these whihc I will show you in the next two steps.
• The 'cursor step' (in red left image) is the speed of the movement of the machine when directing the tool around. This is something to really think of when you are lowering the tool as said before they are very easy to break.

Setting X/Y origin

• Use the arrows in the left hand photo to move the tool to the correct place on the material you have placed in the maachine.
• Once you are happy you can press the X/Y button on the right hand photo and this will set the origin for this cut. You can check this by looking at the number on the left side of the panel described earlier.

Setting Z origin

• Use the arrows in the left hand photo to move the tool down so that it is above the pot of z origin you are wanting remeber don't break the tool.
• Now this going to sound odd but you want to undo the tool but lower it to the bed and this will give you the most accurate Z origin.
• A good thing to also do is bring down the chuck by pressing the Z button down makesure piece is loose in chuck!. This means you will have more of the tool in the chuck therefore it is less likely to be wobbly when spinning.
• Before you press the Z button on the right hand side of the panel you need to lock the tool into place carefully, now press the Z on the right hand side of the v-panel as shown below.
• Just like the X/Y you should see the number go to 0, now move the Z axis up by 3 so that it is no longer on the material!

Putting png.rml into v-panel

• Finally you need to check you have 'user coordinate system' seleted (see iamge below).
• Then you press 'cut' when is at the bottom of the panel next to the yellow button 'pause'.
• This will open up another tab called 'cut', where you now need to drag and drop your piece you are wanting to mill remember to delete all other jobs.
• Now press 'output' and this will start the job!

PCB Fabrication

Trace 1

First attempt cut the outside and part of the inside but then didn't do the middle main traces.

Changing the depth in mods

I changed the depth of the cutting setting in mods so that the machine will but it deeper. I changed it by 0.10 to 0.12 which seemed to work in the end but...

Trace 2 and 3

It still wasn't working and we couldn't understand why, I thought I might have been because of the way I had attached to the bed with the tape. So I decided to change the tape direction on the board and place it on the bed in the middle rather than right on the edge.

Putting the tape the right way around and replacing board into the middle of the sacrificial bed.

Trace 4

By doing these three changes of the depth in mods, moving the board and changing the tape this seemed to work as board 4 came out very nicely!

Assembiling the PCB

I then moved onto stuffing the board which I think is the best way to describe soldering the electronics on.

What you will need:

• Soldering iron (always wet the sponge)
• Sodering power
• Metal scour
• Tweezers
• Leaded solder

Following Brian's Tutorial

'Link to Brians Website'

I picked up all the pieces that was on Brian lists in his document and I already knew that they fitted onto my board as that was one of the first things I did at the beginning. I then placed them of a sheet of paper as shown below with what they are, how many I needed and then the componeted they are connected to. As this was my first time in seeing most of these items I was struggling to rememeber which one is which. I was also struggling to remember what one needed to be the correct way around and what one is more sensitive to heat.

Schematic

So to understand where everything went on the board I had made, Brian had an image of the board which looked like the board but with different lettering which is shown below. Then another image called a schematic and this tells you what direction the component is meant to go also what each letter means in the first image. I made myself a cheatsheet so that I could remember what piece is as in the schematic they are called other names, this is the image above.

Soldering

Right so how to solder, at the Wednesday meeting Niel did show us a little on how to solder. The jeneral jist of it is that:

1. You need to tin your soldering iron (this helps keep it clean and gives a better shiny solder in the end)
2. You then rub it in the metal scour to makesure the solder has gotten around the iron tip
3. We were setting our iron to 330 degrees and using leaded solder which is much better to use
4. ALWAYS start from the inside to the outside, just like lighting a cake - this will help so you aren't hitting other parts as you are sodering.
5. Next you should place a bit of solder onto the trace you are planning on soldering your component onto
6. Then get your component and place this ontop of your sodlering spot, with the tweezer hold this down
7. Now heat that bit of solder and your component should fall into this solder, check it is secure by turing the board upside down
8. If it is fixed you can now do the other areas on this component and then come back to add some more solder if needed on the first trace
9. That is a very basic step by step of soldering
10. When adding more the solder should flow around the component end.

Me doing the beginning of my board, Andrew was with me as I was doing this so got me to do the ATtiny45 first so he could see how I was getting on. I really like soldering, its like following and 3D pizzle but you have to lock the pieces into place and the outcome is a lot more fiddly but worth it.

Resoldering LED

Once I had soldered everything I had a look at my board and thought I had placed the green LED the wrong way around so I took it off and replaced it with a new one and flipped it around.

Finished board!

I finshed off by soldering the USB area this makes a better connected for the PCB to the USB port. Also I soldered the junction on the board which will be broken later on when I turn the board from a programmee to a programmer.

Testing

The next step is to see if this is all working, here is what I did:

• Check components against the images to see if you have them the correct way around or in the right place etc
• Do a Continuit test - I used this machine (see iamge) which determains if there is a current by making a beeping noice.
• You should go through the whole board, checking the components next to each other so there is no short circuit around them, the worst part for this one was the ATtiny and the ISP.

I used a multimeter which is the photo below, this makes a buzzing noice when there is a connection and it also goes through LEDs which is perfect for this. The black lead is the ground so I can test that everything is the correct way around as well as is they are working around the board if there are any short circutes.

Making a Second Board

Everything looked and sounded good so then I loved into making a second board as I wanted to do more soldering, milling and overal thought just in case the first one didn't work I had another chance.

As you can see from the photos something went very wrong! The first image is my board with the cutting out of the tracers not working at all, and the second image is the milling bit which I had broken as I was milling. What happened which I had mentioned above is that I didn't tighten the grubscrew enough when putting the tool into the chuck. I got a very lovely vidoe of it falling and my stomache went as I saw it in real time... but it happens and lucky we had another bit to use and Jonny had cut his boards.

I tried it again and it all came out well, I also cut away the excess copper but I used a scalpel to do this and I didn't want to fisk braking another bit. (see image below)

Assembiling Second Board

I couldn't find the ISP so had to wait till Andrew was back in to help me find it.

Comparing board 1 and board 2

Image 1 - full

Image 2 - using a microscope

Image 3 - using a microscope

Image 4 - using a microscope

An image I took which I thought was rather lovely and showed how I worked in our soldering station

Software Installation

I downloaded CrossPack but Mac has a software called gatekeeper in it that wont let you open downloads if it doesn't trust it. To get around this you need to right click on the download and press open.

This will then open up and you need to click open, this means that you have gone around gatekeeper and it has seen you are clever and know what your doing and it will let you through.

By typing in 'make' into terminal this showed me that it understood there was something new I had downloaded. I then realised the error was because I hadn't told terminal where the download was as it was still in 'home'. So needed to 'change directory' = cd then then paste to downloads as that was there CrossPath is.

There was an error so I processed to google thins error to see what had gone wrong, this is when Andrew saw that CrossPack works on 32-bit and not 64-bit so this software wasn't going to work for me on my MacOS.

Website Step by Step help

So this is when google came in and really helped, we found a website that gave me step by step instruction on what to do.

Follow this link to the website so you can do the same as me and follow their instructions. This is instead of installing CrossPack: MacOS 64-bit Toolchain

This is what I did with some of the screenshots of my processes.

Alot if this I found very confusing and had to take my time to get my head around it, if I'm being honest I'm still not quite sure what each step means but I do understand what I did in each step which is a positive. All I would say is take each step at a time and and makesure that if it isn't working just restart terminal this saved me a lot during this journey.

Step 0: Remove Any Old Toolchain Package

This is me uninstalling CrossPack and double checking by pressing 'ls' which is showing me the list of items I have in that directory I am in. This showed me that CrossPack has now left my directory as I wanted.

Step 1: Install the Arduino IDE

Follow the steps online I then downloaded Arduino as this has the same ability to run 'make' which is what I need to run my PCB board later on.

Step 2: Find the AVR Toolchain

This is to see see if I had added the AVR in my toolchain which as you can see I didn't but I didn't notice this last time and therefore at the end this wasn't working in the next step I'll explain why it hadn't come up in the tool chain. Open a new terminal after this step so that it can refresh itself.

Step 3: Install Link to AVR Toolchain

This is me adding the AVR link to my toolchain, this is where you place some of your items that you have downloaded so that they are remember by your terminal. I forgot to add the link to this section so the rest of it didn't work which is why at the end I was struggling. Sudo is basically overiding all the setting of the termnial so you can go behind, but it can also be very dangerous as you can delete all your information you have in your cloud.

Step 4: Adjust PATH Variable

This is where I should have double checked the AVR was in my path but as you can see it is not so again I had to go back and add it to the previous stage and then it came up in thie stage.

Step 5: Install the "avrdude" Program

This step (do double check the website MacOS 64-bit Toolchain ) but this is so that the Arduino can find what you are doing in terminal.

Step 6: Install a Working "make" Program

So with macOS and this 'make' doesn't actually work very well so I have to use 'make --verison' which you can see in this screenshot.

This is where I realised I had done the presvious stage wrong when it came to the path and putting the link in pico, but after I had done this it worked in step 7!

Step 7: Test Installation

WOOHOO I have now done the whole processes which could have just been 'CrossPack' but we are here now and I can't complain too much.

Tip it is always good to just chekc what terminal is saying, as you can see in the right hand screenshot there is some writing in pink. I know this is fine as Andrew says it is and other have done this before but do always read this areas as this can give you some information that you might not have known.

So this whole step is just the 1 on Brians page which is to do the 'Software Installation' because Brians website is old the software that he suggests now doesn't work on the lastest MacOS as the old one was 32-bit and we are now using a 64-bit.

Get and Build the Firmware

Checking that in my Makefile that it says:

• MCU = attiny45
• Programmer ? = usbtiny
• F_CPU - 16500000UL

This is to set up the programmer that I will be programming my board with so if it has a ATting45 chip then this doesn't need to be changed but if it has a different chip I will need to update this area of the doc.

Programming my ATtiny45

Now back to Brian!

'Link to Brians Website'

Plugging it in

I started by just plugging my board into a USB port to see if anything would happen, and there was a light! Unfortunatly turns out that doesn't really mean anything and that I had a very long road ahead to see if my board was actually going to work...

Making a Ribbon Cable

Getting the ribbon heads the correct away around is a tricky part and by looking at Andrews I managed to figure out how this would work. To get it to clip together was very hard so I used one of our clamps to click the female header together with the other part with the metal spikes. You need to make sure that when you are clamping it the female headers are facing in so that the lines match up with the correct pins. Hope that makes sense.

Future Katie here: this ribbon cable was great and I ended us using my programmer and ribbon cable most weeks to programme my future board! Make sure you get this made correctly and that you keep it, I also added little black dots on the female headers to show which pin was teh GND.

I used my ribbon cable to connect Andrews PCB to mine to programme it, to get this to work I connected Andrews programmer to the computer.

Following Brians instructions I placed my board on the left side (if looking at picture) and then the programmer closest to the computer. Both lights came of which made me happy (whether is a helpful part or not) making sure they are facing the same way (USB port towards computer) I then ran the next step...

This is the command you put in terminal 'make flash' to see if your board is correct, it wasn't working as you can see in the next photo but...

V1 board

Andrew then looked it up and realised we needed to plug both the USB into a socket so then I ran 'make flash' and IT WORKED!

V2 board

I then did it on my second board and THAT WORKED TOO!

This is what terminal looks like when it has gone to plan!

No thank YOU terminal!

Andrew and me realising after 4 hours how to get this sorted! I think you can tell it has been long but deep deep down we are smiling and very happy it has work! wooohooo :)

Test the USB Functionality

This is doing 'make fuses' this is to reset the reset pin, this will let the chip use the reset pin to program other boards, but will disable the ability for this chip to be programmed again.

Version 1 - worked

Version 2 - worked

Checking to see if my USB has shown up in the USB devise tree by going to apple in the top left - click on 'about this mac' - click on 'system report...'' - then on the left side go down to 'USB devise tree' and it will show you if your USB has come up.

Blow the Reset Fuse

My board plugged into my laptop.

This is the point now that we stop it being a programmee and it is going to be a programmer. Doing 'make rstdisbl' this is to reset the pin in the ATting45 reset pin into a GPIO pin which stands for general purpose input output. This can be found in the data sheet of the chip.

Version 1 - worked

Version 2 - error

Version 2 - worked

You then have to desolder the junction that you made at the beginning, I did this just by heating up the solder and then used the solder sucker to get rid of that solder which worked well.

Hero Shot of Boards

Overview

I really enjoyed this week, I love sitting and soldering making sure that everything is correct. Being delicate and careful with the soldering for some reason reminds me of ceramics when you are cleaning your work, or painting this very delicate pot. Its a very satifing activity which I could do for a while. Getting things to wokr on the other hand I do find very hard as I don't think I know enough yet to know what to do or look out for. But over time I'm sure this will become just as enjoyable as making the board itself.

Design Files:

• Neil's line test .png
• Brian's traces .png
• Brian's outline .png

Other Pages:

• Home Page
• Assignments
• Week Three: Computer-controlled Cutting
• Week Five: 3D Scanning and Printing
• My Final Project