Velocity Variable Headlight

Graduation

Tyler — Sun, 21 May 2006 19:03:06 +0000

For Jonathan, Matt, and I, Saturday was our graduation. We are finally done with it all. Evan and Erik both have one more semester, but Evan had the opportunity to join us at the Spring graduation yesterday and walk along with the three of us.

As for our plans…

Jonathan is going to graduate school at UCLA.

Matt is still working out the details with a few job offers.

I will be moving up to Everett, Washington, to go work for Boeing.

We all wish Evan and Erik a good last semester and look forward to hearing their career and/or future education plans.

Second Place!

Tyler — Thu, 11 May 2006 05:17:54 +0000

Somehow it was either our mechanical engineering fortitude and skills or the tight bicycle clothing I wore that got us second place. The classmates voted for all of the projects (you obviously couldn't vote for yourself). Some people complained that our project was too simple, but my answer to them is: "it worked and worked well." No prize money for second place though. Darn.

Roll Credits

hackinjat — Sat, 06 May 2006 19:39:02 +0000

Congrats guys! I posted additional photos from the open house on my flickr account. I also uploaded a video of our project in action.

“If else” will be the downfall of humanity…

Matthew Rosenbrock — Thu, 04 May 2006 18:44:17 +0000

Set the scene: Late Wednesday evening. The entire project must be functional by the following afternoon. But the velocity calculations continue to be erratic. WHY?

Enter Matt.

Matt: Hey, should this "if else" statement just be an "if"?

Jon: Uh…yeah.

Matt: That would be dumb if that solved the whole problem.

Jon: Yeah. Let's try running it.

Running code.

Jon: It seems fine now.

Matt: Son of a B!t&#!

And so ended the war between code and coder.

Stepper motor in a nutshell

hackinjat — Tue, 02 May 2006 05:24:36 +0000

I thought I’d say a few words about how the stepper motor that we have is set up, and how its going to work. Basically, the motor moves 1 “step” (7.5 degrees) each time it receives a specific sequence of pulses on its 6 wires. The great thing about stepper motors is that you dont need feedback to control it; if you know its starting position and how many steps it’s taken, you know its current position.

So, we wrote code to generate the correct sequence for us, using the digital outputs on the board to generate the pulse sequence needed to move 1 step. After the chip calculates the velocity, it determines what the correct focus ring position should be for that position. Because we record the number of steps we command the motor to take, we always know the focus ring’s current position. Using this information, the code moves the stepper the appropriate number of steps to move the focus ring to the desired position, then samples the velocity again and repeats the process.

Now, how does the sequence of voltages from the DSP power the motor you ask? Each of the digital outputs is attached to a transistor. I’m sure you recall that current can flow from the source to the drain of a transistor only when a voltage is applied to the gate. This is used in our design by attaching the source of a transistor to a 5V external power supply, the drain to a motor wire, and the gate to the digital output from the DSP. Thus, when the DSP generates a high signal, it activates the transistor gate, allowing current to flow from the external source to the motor wire. Four of these transistors are used to control 4 wires from the stepper motor coils. The other 2 stepper motor wires attach to the common ground of the coils. With the appropriate sequence, the motor coils are energized such that the permanent magnet rotor inside the motor spins to the next magnetic equilibrium point, i.e. 1 step.

You can see all this on the updated electrical diagram I’ve attached below.

Updated Electrical and Code Flow Chart, hooray!

hackinjat — Sun, 23 Apr 2006 05:37:25 +0000

Now that we have both components of the stepper motor driver, I updated the electrical diagram using the spec sheets for the new IC's. Basically, the driver moves the motor one step for each pulse it receives. It can take pulse signals in the kHz range, meaning that the stepper could (theoretically) move at a couple thousand rpms. Should work for what we need it for. We also need a zenner diode, but these are fairly common so I think we can just find one in the shop.

Also uploaded is the program flow chart describing the workings of the code, before any stepper motor nonsense is added.

Website Changes

Tyler — Wed, 19 Apr 2006 09:59:36 +0000

Take a look around, you'll see some additions and changes.

Initial Wiring Diagram

Tyler — Tue, 18 Apr 2006 18:42:38 +0000

Here is the wiring diagram for the DSP and ICs needed to power and control the device.

Status Check for the Class and Project (As E-mailed by Evan)

Tyler — Tue, 18 Apr 2006 18:38:32 +0000

So today [Monday] was a great day and here's a list of our accomplishments so far Things Done:
Our sensors works
The servo motor works and responds to frequency
The flashlight has been cut and modified w/holes for mounting
The stepper motor is mounted
The parts have all been beadblasted and look sexy, can you say Cal?
The axle has been cut and modified
Everything fits so far
The website looks great
and the other 102 groups are jealous and scrambling

however we're still not done.

We still need to:
Finish the code for the stepper motor and be able to run everything simultaneously
Wire in the electronics nicely
Design and fab the mounting for the power and dsp
Choose and obtain our power supply
Prepare slides and practice the oral presentation
Finish technical report (compile cads, bom, specs and calcs, catalogs and appendix)
Prepare the bike (clean it, blue and gold?, Cal somehow in the frame)
Design and make posterboard ( this should look pro and tie into proof of principle concept)
Complete website( WIP)
Turn in receipts

We are about 2/3 done, but fortunately this last 1/3 is mostly the fluff. Friday is a big day to get the project working and during the week would be a good opportunity to jump in on the fluff stuff. Keep working hard guys and i think we can win this thing, if not we can be damn proud of a very complete engineering project.

Mechanical Fabrication Almost Done!

Tyler — Tue, 18 Apr 2006 18:36:16 +0000

As of yesterday all of the parts to the mechanical design have been fabricated and assembled. All that remains is to lathe out an aluminum sleeve coupler for the stepper motor and gear. As soon as I get the photos from one of the group members, you can see the finished project (minus the wiring and coding of course – that's what we have left to do).