Assignment 4

For Beginners: General understanding about Assignment 4

(Acknowledgment Ivan Hernández help me a lot on understanding this)

For those who know little about electronics like me (I am an Economist), microcontrolers like me this is a simple intuitive introduction. For those who are experts, skip this.

Definition of in-system programming, microcontrollers, mictrocontroller board and circuit board

(Reference Nydal Dahl) and Wikipedia

According to Wikipedia, "in-system programming (ISP), also called In-Circuit Serial Programming (ICSP), is the ability of some programmable logic devices, microcontrollers, and other embedded devices to be programmed while installed in a complete system, rather than requiring the chip to be programmed prior to installing it into the system".

Microcontrollers let you write programs to control several electronics. They are in fact like little robots. A microcontroller works with a circuit board, and this is basically what we need to do for Assignment 4: build a circuit board and/or print a circuit board and add all the additional components. The brain of your circuit board will be the microcontroller. Other important components on your board will be: resistors, diodes, crystal and jumpers.

"There are two ways of using microcontrollers in a project: a) use a microcontroller board, and b)Integrate a microcontroller on your circuit board. Until now I do not understand the difference between the microcontroller board and the microcontroller on a circuit board." (Nydal Dahl)

How to build your circuit board

Required material for the circuit board

In order to build a circuit you need a conductive material. (To learn more about circuits this is nice a website that explains basic concepts about conductivity.) So, we can use some conductive materials to build or print a circuit board: epoxy glass (FR3), phenolic paper (FR1), cooper foil (Aluminum Bonded Copper), teflon, glass, among others.

Once you have a panel of conductive material, you have to take out part of the layer so you create circuits. A good program for doing this is Fab modules the machine we will be working with is called Modela.

Fab modules and Modela

Fab modules is the software to generate the code for using Modela, which will fabricate and manufacture the circuits.

Step 1- Set up Fab Modules in Modela. This was really difficult but eventually we made it happened. On Friday we were still using the original program of the Modela and we print one circuit with the specifications of the Fabmodules but it didn't work. The reason it didn't work was that (what I understood) was that the cutter was cutting on the side and not in the middle. On Monday we were able to set Fabmodules on the computer. And this was my process¨.

1st. You have to open Fabmodules and set in which type of output you want to work, this will be rml. Then it will appear the following image:

a. First, you have to upload the picture where it says load.png which will be the file related to traces.

b. Then you want to specifiy the mill traces of 1/64 which is the size of your cutter.

c. After this, automatically Fabmodules will set up everything. The speed of your cutter which will be 4 mm per second, the depth of the cutter that will be -0.1 in relation to the origin, the intensity, among others.

d. You push make .path

e. You push make .rml

f. Then you send it.

IMPORTANT THINGS TO KNOW. I did this 5 times, because I did several mistakes.

Try 1. First, printing the board was ok, but when I start welding it I make a mess. Apparently I start using a lot of copper that I couldn't take out of the board. I decided that it was better to print another board.

Try 2. Apparently the origin where the Modela started was in 0,0 and that even when you set up fabmodules as 20,20 it started in 0,0. Well, this was not correct, indeed it started in 20mm, 20 mm and it overlapped with another printed board.

Try 3. I used tape to hold my board while it printed in Modela, but the board was uneaven because the way I put the tape. This implied that there were some parts that were well printed and others that were not (See on the right).

Try 4. I manage to print it well finally, but I didn´t use the emery paper correctly so I start getting little copper balls in my board (See on the right).

Try 5. I got again the same problem as try 3. By this attempt I was a little bit frustrated.

By the fifth try I was suspicious that the Modela was not working well, at least in the part about the origin. So I tried another machine.

Summary about what I learned so far about printing the circuit board:

1. Verify that your modela is starting in the point where you are actually indicating.

2. Place the tape behind of your board --the one used so it doesn't move while printing- EVENLY. Especially in the area where the board is going to be printed.

3. Use the emery paper after the board is printed so it is quite soft, and you do not have problems while welding.

Watch the tutorial in YouTube on How to Mill Circuits on the Modela

How to assemble a printed circuit

There are two main suggestions I can tell for starters:

Locating the components is quite easy with the printed circuit

model shown at the right.

1. When you are welding each component, first put some tin

(estaño in Spanish), over the board on the place where the

component will be positioned and then, place it carefully over.

2. I used a toothpick to hold the component before welding.

3. I started welding, first by heating the tin that is over the board,

and pushing the component down with the toothpick.