Tuesday, May 31, 2011

Altoids Audio splitter hack

I needed a quick 2-to-1 1/4" Stereo Jack box for the Church's sound board. This should do the trick!

 The switch either shorts both Jack's Left and Right Channels together or just selects the Right from one jack and the Left from the other jack. I wasn't sure if shorting the channels together would effect the audio quality due to extra loading, so I put the switch in so I could play around with it.
In a nice minty fresh shielded Altoids Box :)

Saturday, May 28, 2011

Tweets keep me Current

My company recently hired an EE intern to work with me and help fix all my mistakes this summer :)  He is very bright and extremely motivated to learn knew things. One of our conversations made me start thinking about all the things I do to try and keep myself learning new things. 

I work at a company that has a relatively small Electrical Engineering group, so I have had to rely on reading publications and allow myself to be taken out to dinner by an occasional vendor to stay current with the latest electronic component offerings.

Trade Mags are a great way to keep up on the technology:
EETimes is more of a current events type mag.
EDN & Electronic Design are a bit more application orientated in there articles.
Embedded Systems Design (ESD) is more software/firmware focused.
Circuit Cellar is a great mag for seeing electronics from a hobbiest perspective, but many of the designs are totally capably of being mainstream products with a bit of refinement.
Design News is a more of a well rounded engineering mag that is more product focused.

There are lots of other more field specific mags, but these are the embedded mags I read religiously.

For the last 9 years of my career I thought these were the major sources of EE knowledge apart from co-workers, textbooks and trade shows. At the Embedded Systems Conference in Chicago last year I did something I never thought I'd do.... I created a Twitter account. They were having a Twitter based scavenger hunt and I was in the mood to collect some nice prizes/swag, so I created an account so I could participate.

A few months later I really started using the Twitter account as a way to monitor companies and individuals who were Tweeting/blogging about electronics. I found a whole new world of people and organizations that were using social media to educate engineers.

I found:
The EEVblog where Dave Jones rants about everything from poor multimeter design to acoustic panels in his recording room study.
The Amp Hour weekly podcast/radio show discussing the embedded electronics industry.

Adafruit, Design Spark, SparkFun , and Element14 who sell parts and/or kits, but also have a ton of content on there sites from blogs to tutorial videos, to just plan rants about embedded stuff.

I've also been able to follow some awesome engineers like Jeri Ellsworth, Chris Gammell, Clive (Max) Maxfield, Dave Jones, Jeremy Blum  and many more who tweet very regularly and discuss topics most Embedded EE's love.

Even though my personal Tweets are minimal it is great following other conversations and getting linked to blogs and videos about projects that stir my imagination and get me excited about being an Engineer.... I just learned about what an Arduino was and have one in the mail to me... fun projects to come, keep Tweeting!

Saturday, May 21, 2011

Neon Blinky Lights

When ever I descibe what I do for a living to people that aren't very technical, I just say "I make lights blink"... which isn't that far off from the truth.....

Last week I dug out an old Analogic AN3100 Precision Voltage Source out of the scrap pile at work.  I love tearing apart old test equipment; especially stuff that was last calibrated the year I was born :)

The display had a couple neon bulbs that were burnt out, but everything else looked in good order.
A little searching on ebay, a week and $2.50 bucks later I had 10 brand new neon bulbs. I replaced the bulbs and this piece of test equipment is as good as new. This will come in handy with some of the home-brew ADC projects I am working on.

Since I had some extra neon bulbs left over I started playing.... I remember back to my first Electricity Class I had in High School. We made the worlds simplest Blinky Light. I strung together a couple bench PSUs so I could get +85VDC, grabbed a 220K Ohm resistor and a 1uF 250V cap. and made a blinky neon bulb RC circuit.
 The neon and the cap are in parallel and the resistor charges up the cap until the voltage hits the neon's voltage; the neon turns on and discharges the cap and the cycle starts all over.

A blinky light and I didn't even need a 555 timer.

I can't wait to show my two little girls when they get home.... Blinky lights are fun, and I am easily impressed, hopefully they will be too!

Saturday, May 7, 2011

Fruit Batteries

Just some good old Fruit Batteries to help stimulate my young brother in-laws imagination. I learned some things too... like the voltage generated is based on the two metals used and not the "acid" inbetween.

Wednesday, May 4, 2011

House Cleaning.....

It is a sad day.... I am officially retiring my 68HC11 Axiom evb that I bought back in college. It was my first micro eval board I ever played with. Good bye Buffalo monitor.........

I was also digging through my old projects and found this cool LED Blinker dealio I built. It is a 555 timer driving a PLD that is sequencing a row of LEDs... I had fun my graduate year in college :)

The Technology of Behavior Modification

Several years ago a local non-profit organization contacted me about helping them with a service they were providing the community. This non-profit takes donated vehicles, fixes them up and sells them a hair above cost to individuals that have "less-than-perfect" credit. This non-profit provides all the financing to the individuals and when the monthly bill is due they would also take that opportunity to teach the vehicle owners basic car maintenance.

When this program first started out they were struggling to keep it afloat. You see many of the individuals with "less-than-perfect" credit got that way because they had a hard time prioritizing their bills and this non-profit was having an 18% default rate on the financing they were providing. Since they could not afford to repo these vehicles, the non-profit started using "payment protection" devices. These devices are Starter Interrupt Devices that behave like an alarm clock except they count down to 0... like a bomb. Instead of blowing up when they hit 0 they disengage a relay that is connecting the ignition key to the vehicles starter; thus preventing the vehicle from starting again once it is shut off.

This sounds very 1984 "Big Brother-ish", but these devices help the individuals make paying the monthly car payment a higher priority. Once these devices were installed this non-profit went from the 18% default rate down to less than 2%. This non-profit's program is now one of the few similar programs in the state that is completely self sufficient and relies on no state or federal funding.

Where I came in was the non-profit was not happy with the Payteck device they were currently using. It was too expensive, complicated to use, and relied on a keypad in the vehicle to update the new payment due date. This keypad was constantly breaking due to pop spills and other abuse.

I designed a device that was low cost (less than $50) and is pretty simple to use. It has a dual seven-segment LED display to show how many days are left before the payment is due, a DB9 serial port connection, and a cable that attaches to the relay that controls the key ignition. The device also comes with a keychain dongle that plugs into the DB9 connector. This dongle when plugged in allows the individuals 1 more additional "911 emergency start" even if the payment was past due. The non-profit could then "recharge" the EEPROM based dongle to add additional emergency starts; they use this as a means of collecting late fees. The dongle is also used by the non-profit to reprogram the new due date into the devices.

The design was based off of a Silicon Labs C8051F300 8-bit micro and a (now obsolete) Maxim MAX6902 Real-Time-Clock. The circuitry is pretty straight forward: a LM317 regulates the vehcile's voltage down to 3.5V, the MAX6902 keeps track of the time, date, and alarm date in its CR2032 coincell backed RAM,  a RS232 port connects the device to a PC, and a buffered SPI bus connects the micro to the EEPROM dongle.

The 2-sided 2-layer PCB was laid out using Cadsoft's EagleCAD.

The C code to control the device was written using Silicon Labs IDE and an open source compiler, SDCC.  It took a bit of work converting the original code I started writing in Keil to SDCC, but the price tag was right. SDCC's code is about 2x as big as the Keil code, but 8KB flash was enough to get the job done.

I also wrote a Windows app with Visual Studio 2005 to program the devices time, date, alarm date, and program the Key Chain EEPROM dongles via a com port.

Overall the non-profit was happy with how these devices turned out and bought 27 of them from me. I was also very pleased with how well these devices worked. On the next revision I'd like to get rid of the RS232 port and replace it with a USB device port. Replacing the custom EEProm dongles with SD Cards or USB flash drives would be nice as well.

There are quite a few companies that manufacture these Starter Interrupt Devices and they span simple devices like mine all the way up to GPS & Mobile Phone enabled units that can be reprogrammed wirelessly. The letigation is interesting to read about as well. Many of the companies have been brought to court for "endangering" the driver when the device disables the starter. Based on what I've read the Starter Interrupt manufacturers have always won the court cases, becasue these devices don't shut off the vehicle, they just prevent it from starting. Also everyone of these devices including mine have an "Emergency 911" way of starting the vehicle a limited number of times in case of emergency even if the payment date has passed.

Anyway this is interesting "Behavior Modification" technology and even though it is a bit "Big Brother-ish" it does enable people with "less-than-perfect" credit (i.e. scores less than 400) to finance a vehicle.