Quick python terminal

I like Python, it seems like it takes no time to make something that works.  Last night I found an example of a simple scrolling text box GUI done using Tkinter.  After an hour or so of modification it is a pretty usable terminal app. I posted the code here for everyone: http://www.mybitbox.com/mbbfiles/s1axter/pyterminal/

I am working on using this for a serial terminal. The idea is to have a program class that has a handle to an instance of this terminal, a serial port and a communication class.  If there is a local output function in the program class you can send text to the terminal rather than stdout.  Also, bind all keyboard inputs to a function in the program class and bingo, simple serial terminal.

More to come.

Formula Car Gear Circuit

My brother is senior at Virginia Tech and is a memeber of the VT Formula SAE team which designs and builds vehicles for national competitions.  This week he told me the driver was having a difficult time managing the car and knowing what gear they were in.  One of the team members suggested a shift monitor that could read an analog signal from the engine and display the current gear.

There is a poteniometer attached to the transmission that outputs voltages in different gears.  Since the transmission voltage ranges are not uniform between gears I used a ATMega8 microcontroller with onboard analog to digital converter to read the voltages and determine the proper range.  Here are the ranges (btw, there is no gear 1)

Gear 1 - Display 0 - 4.88v to 5.00v
Neutral - Display 0 - 4.40v to 4.88v
Gear 2 - Display 2 - 3.80v to 4.40v
Gear 3 - Display 3 - 2.00v to 3.80v
Gear 4 - Display 4 - 1.00v to 2.00v
Gear 5 - Display 5 - 0.26v to 1.00v
Gear 6 - Display 6 - 0.00v to 0.26v

The dash on the car has very limited space so I separated the 7-seg from the control circuit.  Seperating the 7-seg the control circuit can be in a box away from the driver and the small display mounted on the dash.

Here are a few photos of the setup http://www.mybitbox.com/gallery/gallery.php?g=vt_circuit

And also a demo video of how the system works http://www.youtube.com/watch?v=dHIJK_iaXzc

For those interewsted in the code, here is a link to a ZIP of everything.  This code compiles on linux using gcc-avr and can be downloaded to an ATMega8 using a Dragon AVR USB programmer on Ubuntu if you have avrdude installed.  Also, here is a schematic of the final circuit.

Simple Breadboard Regulator PCB

I recently sat down with my new favorite Linux PCB program Kicad and developed a simple PCB for a 5V breadboard regulator.  The idea main goal for this PCB is not to develop the ultimate breadboard power supply but to learn Kicad and how to get a PCB done professionally.  I’ve done a bunch of DIY PCBs in the past with “eh” results, thus, this time I am going to get a PCB made professionally from BatchPCB.  BatchPCB is a spin off from SparkFun Electronics and combines small prototype orders into full pallet runs.  There is a few weeks lead time but if you can wait it looks like the best option for DIYers.

I’ve learned a lot about PCB design in Kicad by looking at personal sites and tutorials and wanted to share my Kicad project with others.  Here is a ZIP file with all the project files.  I also use a custom library for the parts and footprints (much easier than using pre-made ones, which usually don’t work)

http://www.mybitbox.com/browser/files/s1axter/simple_bb_reg.zip
http://www.mybitbox.com/browser/files/s1axter/kicad_libs/