Electronics Production

This week I had to :-

1)To mill out the PCB for the Fab ISP Programmer
2)Install the Required components on the PCB
3)Test the FabISP programmer
5)Programm the PCB as an ISP Programmer

The machine and the PCB production process

In my FabLab, the PCB Milling machine model is SRM-20 .

Here are the few features of SRM 20

This machine can be used for PCB milling and drilling other than that this machine can also use for Cuttable Material of Modelling Wax, Chemical Wood, Foam, Acrylic, Poly acetate, ABS.

X, Y, and Z Operation Strokes203.2 (X) x 152.4 (Y) x 60.5 (Z) mm

Workpiece table size232.2 (X) x 156.6 (Y) mm

Distance From Collet Tip to TableMax, 130.75mm (5.15 in)

X-, Y-, and Z-Axis Drive System have stepping motor

Operating Speed is 6 - 1800mm/min

Spindle Motor is DC motor Type 380

Interface is USB

Cutting Tool Chuck with collet method

Spindle Rotation Speed can adjust i.e Adjustable 3000 - 7000 rpm

Dedicated AC adapter: AC 100-240 V ±10%, 50/60 Hz

Machine Setting

We are using the Monofab SRM 20 milling machine for designing the FabISP.

1) Setting Up the Sacrificial Layer

We will be using a copper clad board as our sacrificial layer.

We need a sacrificial layer here because in case something goes wrong and the milling

bit goes further than expected, we might just end up damaging the base plate.

The sacrificial layer as the name suggests sacrifices itself for saving the base plate from any damage.

To do this we apply the dual sided tape onto a copper clad board, about the same or of greater size to that of the plate we are going to mill. This would also help us when we are cutting the final board out. Make sure that when you place the board on the build plate you leave a 1 sqcm border. Make sure that the board is level and apply sufficient force above it to make it adhere to the base plate.

Milling of PCB

The purpose of this assignment is to characterize the design rules of our production process.:
1- First of all, we saved the test image in our PC as .png format.
2- Then, we opened the fabmodules to convert the picture to a file that our machine can understand.
3- We clicked on input format > image (.png) > and we chose the image that we have just saved.
4- After the image import, a new column called “output” appeared. We chose “Roland mill” option.
5- After that, another column appeared (process). For the process, we used the (1/64) to make the traces of our PCB and the (1/32) to cut through the piece.
6- Then we chose the machine “SRM-20” because that’s the one we have.
7- For the setting on the right side, we set the x, y and z to 0, 0, and 0. The speed to 3, and the zjog to 12. These are the recommended setting.
8- Then, we clicked on “calculate”. The red lines show us the movement of the machine while milling.
9- Finally, we clicked on “Save” and the file will be saved as .rml
Moving to the machine software (Vpanel for SMR20) and the physical setup, we did the following:

Prepare to create .rml file using mods

In 4th step it needs to change the x,y,z to zero and in home section z make to 5 mm.As manually i will do the origin setting though the  v panel.hence the .rml file creation time it need to care about set origin and home only the z axis have to 5 mm. I did mistake at the time .rml file creation.i was putting it as zero hence it was getting wrong at the time of end the milling job the time of milling.It was jut put a milling from the end to origin i.e z axis is not getting up after milling completion.

It is required to delete the websocket from the localhost which can provide to save file to local system, hence it very important to first save the.png file of both trace and cut for the circuit to mill the PCB.

For tracing the mods calculation, here it can be put the maximum milling using my SRM 20 maximum i,e. .005 mm. The x,y and z axis can also be defined.

Now we need to set zero for x, y, and z for this Milling which will be a User-Friendly VPanel The SRM-20’s VPanel controller provides a simple interface for adjusting tool position and moving the cursor to set the milling starting point. The VPanel also allows easy control of the feed rate and spindle speed with pause and resume operation, plus tracking of X,Y,Z axis milling with a numeric readout in millimeters or inches.

Select traces png file in the mods after V Panel setting and press calculate in mods, which will give us the .rml file to be send to the Monofab SRM 20 to be milled.

Soldering the Circuit:-

Now to solder the required components and put the solder just close to it as the heat in copper layer and then solders melt in same time to remove the solder then automatically solder will deposit into the printed circuit.

First Check the board against the schematic and PCB layout image to make sure that you have installed the correct components in the correct locations and orientations. Inspect your board visually. Components should be flat on the board, not tilted with pins in the air. Soldering connections should be smooth and solder should have flowed both onto the pin and onto the pad. If you still see a lot of exposed copper on the pad or the solder is lumpy and draws up into a point where you removed the iron, you probably don't have a good connection. Reflow by applying heat and flux and also look for unwanted solder bridges between nearby traces and pins. Use a multimeter to check for shorts between VCC and GND

Programming the Micro controller:-

Install Necessary Software for AVR Programming:

Power the FabISP Board

Then connect the FabUSB ISP to your PC to supply the power of 5V to the ISP board and attach another programmer like ATmel ac shown in picture.

Then I changed the programmer and followed the whole excercise from the begining.

I Typed

avrdude-c usbasp -p t45 -v
//(here i had made attiny44 to attiny 45 (t45))

It was showing success but on plugging my FAB ISP to USB port of PC it was not detecting.

For solving the problem I found that due to the wrong firmware upload of attiny 44 was uploaded in our FAB ISP Attiy 45. Accordingly, I downloaded the correct firmware. But as per our instructor Mr.Sibu, the firmware cant be over written in the same microcontroller. So either i have to change the micro controller or reset the fuse. So I decided to reset the fuse. For this he instructed to connect the 20 Mhz SMD Crystal Oscillator to Pin No 2 and Pin 3 and center connection to Pin 4(Ground) of the Micro-controller. For this i need to remove the two resistors from pin no 02 and 03 and connect thed oscillator. As I am using Windows10, my colleague Tapas used Ubunut OS. Linux is the premier choice by developers of embedded applications for several reasons: from being open-source to scalability, developer support, and tooling, myriad arguments justify why Linux is a great candidate for embedded systems. In Ubuntu CLI terminal the programing is easily done. Oscillators generate the heartbeat of every micro controller and produce clock signals that are essential for synchronizing internal operations. In micro controllers, the clock signals can be generated using either mechanical resonant devices or electrical phase shift circuits. external clock of 20MHZ frequecy, I need to set fuses accordingly before programming.

Then I used my ISP to programm the FabISP of my collegeue and type the command on my terminal from the firmware directory

>Avrdude -c usbtiny -p t45 -v

and then run the following command

>make flash
>make fuses
>make rstdisbl

Here is the full video of the whole excercise recorded with Asciinema