Electronics Design

The target of this module is to introduce PCB designing.
I have already done a few circuit designs, rather redesigned a the Fab-ISP key version to include two LEDs and replaced the crystal and two capacitors with a resonator. The documentation is available here.

EAGLE is the preferred PCB design tool for me. I have been using this tool for some time. I have used a few other tools before, like PCB123, KiCAD and I have a little bit of experience with Kokopelli.

These are the Eagle Files for the FabISP-Key redesigned with LEDs.

There are few more designs I made for various purposes. One such project is about making a DIY Soldering Station, basically a controller for the Weller PES51 pencil. I designed a PCB which

1. Will amplify the signals from temperature sensor in the Pencil,
2. Has a MOSFET to control the power delivered to the pencil,
3. Has an NTC temperature sensor for getting the room temperature for accurate control of the iron.

Pictures

EAGLE Files for the Amplifier Board, these have some errors fixed, these are not the same as above diagrams show.

EAGLE Files are here

The pictures are here.

Programming a 20MHz board.

This is not compatible with any of the standard Arduino boards, because this board uses a 20MHz resonator. All the standard Arduinos using Atmega328p is running at either 26MHz or at 8MHz. It was my first time making a custom Micro-controller board. So I looked around to see who else has made a 20MHz version, many Fabduinos are like this, so someone must have the required instructions.
I found a page of a previous fab academy student Amir Lazarovich, he made a 20MHz Fabduino and he shared the required files, the Makefile, the boards.txt file and the bootloader. I used these files to program my board, I copies the boards definition from this file and added a few on my own, these definitions were appended to ~/.arduino15/packages/arduino/hardware/avr/1.6.10/boards.txt. Similarly I modified the Makefile located at ~/.arduino15/packages/arduino/hardware/avr/1.6.10/bootloaders/atmega/ to suit the new board.

Though the documentation by Amir was really helpful, I couldn't get the Arduino IDE to program my board, I was getting an error Error while uploading: missing 'upload.tool' configuration parameter. Then I found https://github.com/arduino/Arduino/wiki/Arduino-Hardware-Cores-migration-guide-from-1.0-to-1.6 and I followed this to edit my boards.txt file further. This was due to some additional requirement by the new Arduino IDE. Finally I could program my board using my UsbTiny-FabISP.
This is a video of the board being programmed I made for Electronics Production Week.

The Makefile, boards.txt and the hex file can be downloaded below. The location of the files as in my system is also shown.

Few Resources I Found Useful

• Overclocking ATMega328P
• ATMega328P - Burning bootloader
• Recovering from a "locked out" AVR

The Arduino Permission Fix

You may find that you can't use Arduino IDE to program your board unless you start IDE as 'root'. There is a fix for this.

After installing the Arduino IDE in Arch or Arch based Distros like Manjaro, you need to add yourself to a few groups so that you can access serial devices.
gpasswd -a $USER uucp
gpasswd -a $USER lock

Define the correct udev.rules. For the Arch based distribution which I use, I created a file /etc/udev/rules.d/50-embedded_devices.rules

# USBtinyISP Programmer rules
SUBSYSTEMS=="usb", ATTRS{idVendor}=="1781", ATTRS{idProduct}=="0c9f", GROUP="users", MODE="0666"
SUBSYSTEMS=="usb", ATTRS{idVendor}=="16c0", ATTRS{idProduct}=="0479", GROUP="users", MODE="0666"

# USBasp Programmer rules http://www.fischl.de/usbasp/
SUBSYSTEMS=="usb", ATTRS{idVendor}=="16c0", ATTRS{idProduct}=="05dc", GROUP="users", MODE="0666"

# Mdfly.com Generic (SiLabs CP2102) 3.3v/5v USB VComm adapter
SUBSYSTEMS=="usb", ATTRS{idVendor}=="10c4", ATTRS{idProduct}=="ea60", GROUP="users", MODE="0666"

#Atmel AVR Dragon (dragon_isp) rules
SUBSYSTEM=="usb", ATTRS{idVendor}=="03eb", ATTRS{idProduct}=="2107", GROUP="users", MODE="0666"

#Atmel AVR JTAGICEMKII rules
SUBSYSTEM=="usb", ATTRS{idVendor}=="03eb", ATTRS{idProduct}=="2103", GROUP="users", MODE="0666"

#Atmel Corp. AVR ISP mkII
SUBSYSTEM=="usb", ATTRS{idVendor}=="03eb", ATTRS{idProduct}=="2104", GROUP="users", MODE="0666"

#Atmel Copr. JTAGICE3
SUBSYSTEM=="usb", ATTRS{idVendor}=="03eb", ATTRS{idProduct}=="2140", GROUP="users", MODE="0666"
      

Resources

• Getting Started With Arduino on Linux (Ubuntu)
• Installing Arduino on Linux
• Install Arduino on Ubuntu Linux
• Arduino On Arch/Manjaro

Problems

I had one major issue so far, the ISP connector is soldered on very thin pads and some pressure on the ISP pins pushed them inside through the holes and the pads came off and lost the connection to the traces. I fixed it somehow using thin copper strands and glue gun, but it's not a good or reliable solution. A better solution would be to use a thicker pads or add rectangle section ion eagle to make the pads bigger, like in the figure below.

Exploring Further.

I know, I have done more than enough for this modules assignment. But most of the above circuits were made before or an existing design or not something unique and I have a week to do something, I'm exploring a few options. I have a few ideas, few things I needed, so I might be making one or more of the below list, when I get time. See below or keep reading the following pages to find out what I have made.

1. A 12V lead-acid based DC UPS for the 3D printer: This is also useful (with some modification) as a Desktop UPS as the normal UPSs convert the 12V to 230 V AC and then the SMPS inside the PC converts it again to 12V, 5V and 3.3V. So I can improve the system efficiency if I were to use DC-DC converter to generate a stable 12V, 5V and 3.3V from the Lead-Acid battery directly.
2. A servo tester, a small board that supplies PWM signals to test the servo/BLDC motor. The PWM duty cycle will be controlled by a rotary switch. Something like the one seen at HobbyKing or this Instructables.
3. A stepper tester similar to above.

EDIT:- You can continue to module 11, Input Devices