Motor Testing Platform

The first thing I did was figure out how to use my programmer with the Atmega 8 Microcontroller.  I'm using a SainSmart USB Programmer. The pinout of the Atmega 8 µC can be found here, the pinout of the programmer can be found here.  I used a multimeter to test the continuity of the programmer's cable to match up the pins properly.  I built the circuit shown below on a breadboard.  The LED array on the right is connected to 5 output pins.  When the circuit is connected to a PC via USB the programmer will provide 5V to the circuit, so there is no need for a separate power source.



I used AVRDUDE on Ubuntu to program the µC. While it is available on Windows, it must be run from the command line and the user must find and install the appropriate driver. No driver was necessary while running Ubuntu, so I used the opportunity to become more familiar with the OS.  Note that if you are running a virtual machine version of Linux, make sure the VM has access to USB devices, otherwise avrdude will complain about not being able to find the programmer.

Due to Ubuntu permission settings that I do not understand, I had to prefix all of the following commands with "sudo".  This allows avrdude to run with administrator rights.

The first step is to test if avrdude is able to connect to the µC.  Plug in the USB cable and type "avrdude" into the command line to see a list of options.  Next, determine the type of your programmer.  Typing "avrdude -c asdf" will display a list of programmers.  The Sainsmart programmer is a "usbasp" programmer.  Next, specify the type of microcontroller you are using. Typing "avrdude -p asdf" will display the list of microcontrollers avrdude supports.

Typing "avrdude -c usbasp -p m8" will display the following if avrdude is able to connect to the µC.  If you get an error, check the connections between the programmer and the µC.  Otherwise we are ready to load the program.


The Atmega8 supports C, so if you know what a for loop is you're ready to start writing and running code.  The code for this project can be seen below.  This code sets the B pins to input mode and C pins to output mode.  When Pin B1 is high, the controller counts from 0-15 in a loop and displays the binary number on the LEDs connected to the C pins.

For now, the only difference between beginner C programs and µC programs are the inputs and outputs. You're probably used to using printf or cout to display output and scanf or cin to take input.  Here, our inputs and outputs are high/low states of pins being watched or set.  For example, the line of code to turn on an LED connected to PB0 is "PINB = 0x01".  Note that this will set B 1-5 to low.  AVR C supports logic expressions.  To toggle the state of PB0, type "PINB ^= 0x01" (^= is the XOR function).



Once your code is complete, it needs to be compiled into code that the µC can actually run.  From a command line, navigate to the directory containing your code and run the following commands.  I'm unfamiliar with what each one does, but the end result is a .hex file that can be uploaded to the µC.





We're now ready to load the code onto the µC.  Use the following command:

sudo avrdude -c USBasp -p atmega8 -U flash:w:hello.hex:i

You should see the following in the command window:



The µC will begin executing the code immediately!

I'm an Electrical and Computer Engineering student at University of Illinois - Chicago.  I've joined the Engineering Design Team, where we design robots to compete against teams from other schools.  This video shows one of our robots at the Jerry Sanders Design Competition at UIUC in January 2013.  EDT fields a number of robots for different competition, some robots controlled via RC while others act autonomously.

As a new member of the team, I was given the option of choosing from a number of side projects that will support EDT during design and competition.  Some of the projects were to design a lift for running tests on one of the autonomous robots, a trailer which provided shelter and power for field tests, and custom built boxes for a new set of breadboards the team recently purchased.  I decided to work on a fourth project, a DC motor testing station.

EDT uses a number of different brushless DC motors for its robots.  While these motors are specified to output certain ranges of RPM and torque at different levels of current and voltage, the team needs to know exactly how each motor will perform so there are no surprises in the middle of a competition.  The station will provide a mount and enclosure for the motor being tested, automatically run the test, and then output the data to a USB stick or possibly to a connected PC running custom software to interpret the data.

I chose this project because it will require a large range of engineering knowledge, from electrical and mechanical design to hardware and software programming.  My previous design experience is limited to class work and arcade controller design, so this will be a great opportunity to expand my skill set in a short period of time.

This blog will detail my progress.  Since my background so far is in electrical engineering, I've begun at the input side of the motor, measuring the voltage across and current through the motor.  I'm doing this with an Atmega8 Microcontroller and the majority of my initial posts will be on this subject.