Individual assignment on Electronics Production

In this week we deal with Electronics production. we have to milled the given design of Fab ISP(PCB) stuffed it with given components and program it with following steps.

About SRM 20

Download the circuit image.

Roll of Mods Software

Operating SRM 20 Milling Machine

Stuffing the PCB

Programming through Software

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About SRM 20

In Vigyan Ashram we have monoFab SRM-20. It is machine on which we can mill a PCB (Printed circuit board). This machine have a fully-enclosed cabinet. It reduces the spread of dust and noise in the surrounding. The cabinet of SRM-20 is made of glass, due to which we can see the progress of milling. It has an intelligent safety interlocking door which can automatically pauses the machine when it is open. This feature will avoid possibility of any human harm or accident. But this machine does not have the provision of light in it. If we have to mill the pcb at night we can not see the progress clearly due to absence of light. Because of which many time we can not see the errors in our board and the damage of end mill.

Specifications

Work area:8"× 6"× 2.38"

Loadable work pice size:8"× 6"× 2.8"

Table size:9.14"× 6.17"

Max Tool size:1/4" or 6mm

Spindle Speed: 3000-7000 rpm

Operatinfg speed:1.18 in/sec or 30 mm/sec

Mechanical Resolution:0.00008in or 0.002mm

Acoustic Noise level:45-65dB(A)

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What is PCB?

A printed circuit board (PCB) mechanically supports and electrically connects electrical or electronic components using conductive tracks, pads and other features etched from one or more sheet layers of copper laminated onto and/or between sheet layers of a non-conductive substrate.(Wikipedia)

What is ISP?

The FabISP is an in-system programmer for AVR microcontrollers, designed for production within a FabLab. That is, it allows you to program the microcontrollers on other boards you make, using nothing but a USB cable and 6-pin IDC to 6-pin IDC cable.

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Download the circuit image

Download available circuit design from "Electronics Production Week" page from the schedule of "Fab academy 2021".

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Roll of Mods Software

MODS community edition is a fork of CBA mods research project. mods is a modular cross platform tool for fablabs. It is based on independent but interrelated modules. mods could potentially be used for CAD, CAM, machine control, automation, building UI, read input devices, react to to physical models, and much more. The possibilies are endless.

MODS Origin is a cloud-based interactive, integrated, and intuitive tool developed along side a leading EPC to make sure they have the right tool for the right job. (Internet source)

It is acts as a interface between our operating system and machine(SRM-20). We can also use mods for making a program for any machine as per our requirement. If we want any additional feature in our machine then we can build a program for our machine in MODS.

For milling FABISP i am going to used SRM-20 PCB milling machine. This machine required traces,hole drill and outline rml file. To generate the traces and outline file go through the following procedure

Boot the Desktop terminal using Ubuntu OS.

Open Terminal and use commands



cd Documents to change directory.=> mods => bash mods



Again Open New Terminal and use commands

Cd Documents => http – server





This will open a Window in Google Browser.



Right Click in the Window

Four options will be displayed like Modules, Programs, Edit, Options etc.



Select Program=>Select SRM20 mill=>PCB





Select the Image,Check the format of the image (.png)



Select the mill trace 1/64” for PCB traces.

Select the mill outline 1/32” for PCB outline.



Once we select the end mill all the parameters get set with its standard value.if any one want to repassed then he or she will changed the parameters.

Tool Diameter: It repsent the diamenter of end mill.

Cut Depth : Amount of depth that will be cut per pass.

Maximum depth : Amount of depth that will be cut in total

Offset number: Number of out lines.

Offset step over : Stepover is how far from the previous cut the next cut occurs. A cut it made, the bit is "stepped over", and the next cut is made.



Select the calculating option.we can see the path of our module program the way through png image converted into rml the language under stood by SRM 20 machine.



Click on the open socket.set the speed of of milling machine.Set the origin at home position, then set according to X, Y, Z axis position.



Note that machine head moving along X axis, Bed moving along Y axis and end mill along z axis.



Again click on calculate , it will trace again. Click on open socket and finally click on send file to device.



The SRM 20 machine will accepetc the command and start milling.

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End mill Vs Drill bit

About End mill

the carbide end mill is the most widely used milling cutter tools on CNC machines.

They can be cut simultaneously or separately, mainly used for plane milling, groove milling, step face milling and profiling milling.

The common milling cutter diameter is 1~25, less than 1mm, and it is often called the micro-diameter.

About Drill bit

It is a kind of equipment used in drilling engineering.

it is mainly used for drilling, which is divided into through holes and blind holes (respectively referring to the original holes for reprocessing, and the original holes without holes to drill).

The general processing size is 2~40mm.

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Operating SRM 20 Milling Machine

Open the panel of machine and set the set the sacrificial layer on the bed.

Take pice of FR-1 type PCB material , clean it with acetone , stick two way tape on lower surface .avoid the formation of air bubble.









Now apply the blank PCB on the sacrificial layer with even leveling.



Appling Blank PCB



Even Leveling

Now closed the machine panel . Note that for milling operation machine panel must be closed.

Start the machine, initially the head will set to the home position.

Select the proper end mill as shown in images



1/64" end mill for milling trace



1/32" end mill for cutting trace

For milling operation used the 1/64” end mill. Open the chuck of the milling machine with allen key with anti clock wise rotation.



Opening of chuck



Applying end mill.

Place the end mill care fully and tight it carefully and gently in clock wise direction.

Initially set the origin such that the Z axis i.e end mill is at slight above the PCB surface.

Now open the chuck so that the end mill touch the PCB surface,now tight the chuck screw gently,note the Z axis value. This is called gravity setting.

Now finally set the origin for milling process.



Same process is repeated for cutting only by replacing 1/32” end mill and select cutting.png image.



Now PCB is ready for stuffing.



Milled trace



Cutout milled trace

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Stuffing the PCB

After the milling processed the PCB is ready for soldering, Different components are mounted on the PCB.

The list of components .

1x ATtiny45 or ATtiny85

2x 1kΩ resistors

2x 499Ω resistors

2x 49Ω resistors

2x 3.3v zener diodes

1x red LED

1x green LED

1x 100nF capacitor

1x 2x3 pin header

Sorted the above listed components.

Few things related with soldering

Used Twizzer When soldering the any SMD components on PCB .It helps to pick or hold the component and to solder in it correct position.

Used flux on the PCB it is useful to make a strong bonding of electronics component on the copper. I have used tin lead material for soldering.

For soldering stuff the entire component on PCB board and place the entire component properly on the edges of PCB.

Connect all the component precisely makes sure that there is not made any short-circuit

Problem I have faced

It is difficult find the anode and cathode of SMD Zener diode.there is line mark on cathode,check it carefully.

Note that normal diode is connected in forward bias and Zener diode is connected in reverse bias.

Check resistror value correctly,used google.

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Programming PCB through Software

After successfully completing the soldering process you have to program our ISP board through Linux or Windows operating system.Fab Academy provides an instruction for software installation in PCB. All the instructions are vary as per operating system.In our FABLAB Linux operating system has already installed on one pc.

Though I used windows 10 operating system,have gone through" Atmel AVR Toolchain for Windows".

For windows the process was slightly crirical.
Goto the Fab Academy 2021 Schedule=>Assienment"Electronics Production"=>individual Assignment"in-circut programmer"=>in system developement"Brian"=>go to Windows instillation process click on "Here"=>Goto Install the Atmel GNU Toolchain and download "Atmel AVR Toolchain for Windows"

Steps follows on Windows Operating System

Firstly its need to install Git, we have alredy Git Bash. so click on start menu, search "Git Bash" it will get open.

Download the Atmel AVR Toolchain for Windows from Atmel's site and run the installer. When asked where to extract the files, click the button and navigate to C:\Program Files, then click Extract.



Download Gnu Make and launch the installer.





Download avrdude. Unzip the archive, and copy the archive inside to C:\ProgramFiles.





Then go to the Start menu and search "Advanced System Settings". Under the Advanced tab, click the "Environment Variables" button.



Under User variables, select "Path" and click the Edit button. If you don't already have a variable called "Path", click the New button to create it, enter "Path" without the name, and fill out the value as described below. The three values to add are:
C:\Program Files\avr8-gnu-toolchain\bin
C:\Program Files (x86)\GnuWin32\bin
C:\Program Files\avrdude





Now all software were installed.

Download the firmware source code and extract the zip file on desktop. Open your terminal program and cd into the source code directory.



let’s check whether all are working or not?open the "Git Bash" from Start Menu>apply the command> cd Documents/fts_firmware_bdm_v1then press enter.



run "make"command and press enter>this command is OK.This will build the hex file that will get programmed onto the ATtiny45.



Now comnect the Fab ISP to the laptop with the another programmer through the connectorsThe LED will glow in both the ISP



Now type “make flash” press enter>this command show the error as shown in the image

This means that avrdude successfully found your programmer, but failed to talk to a target board because some of the compnents were not connected properly



So recheck all the connections. In my fab ISP one pin of ATtiny45 was not connected properly. Connected it again checked the ISP.

Now again run “make flash” press enter> this command were run shows the message.This will erase the target chip, and program its flash memory with the contents of the .hex file you built before. You should see several progress bars while avrdude erases, programs, and verifies the chip.Once you run the command the LED start blinked as shown in image.



Video when "make flash" command were run

Run “make fuses” command. This will set up all of the fuses except the one that disables the reset pin.Again, you should see several progress bars from avrdude.



Run “make rstdisbl” command. This does the same thing as the make fuses command, but this time it's going to include that reset disable bit as well. You should see some progress bars, and with that, avrdude will never be able to talk to this chip again through the ISP header.



Now finally check the device manager ,the Fab ISP was recognized and here it was.

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Learning out comes

In this week I have studied various characteristics of SRM-20.

How to operate SRM-20 by giving commands using Mods Software

How to stuffed and solder SMD electronic components on raw PCB board.

How to program FABISP by using Windows operating system through Git Bash.

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Downloads

Brian FABISP Traces.

Brian FABISP Outline Cutout.

Link for Installing the toolchain on Windows.

Download the make file.

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