Owning an Older Car

Written 2015-09-21

Tags:Automotive Toyota Maintenance 

I have a car. I've had it for about 8 years, and it's 14 years old.

The oldest maintenance record available to me is from around 45k miles. Now it's nearly to 150k. This car was never a great car, not as luxurious as a friend's 1980s diesel Mercedes currently being restored, nor a particularly efficient car - only 25 mpg on the highway if I'm careful. It was once the nicest car I've owned. It has since aged.

But, it was the car I needed at the time. Back then, nearly everything I owned fit inside it. Rugged enough to cover my local mountains, the Ozarks, we've travelled from Missouri; to Kansas; out through Denver, Colorado; up and down Pike's Peak; Manti-La Sal and Fishlake forests in Utah; twice to DEFCON in Las Vegas, Nevada; toured Los Angeles, California; driven the crusty salt-lakebed of Salton; crossed the Rockies in Arizona and New Mexico; seen the abandoned towns of dust bowl Texas and Oklahoma; before dodging tornadoes all the way home through Kansas. Toured hackerspaces in the Des Moines and Quad City, Iowa; Chicago, Illinois; and Madison, Wisconsin. This summer I helped a friend move to the middle of nowhere, Nebraska, for a new career. We've seen bear, turkey, white-tailed and mule deer, hawks, eagles, and falcons, and any number of things forgotten. We've spent an entire oil change on a single trip, narrowly escaped being cut off by a forest fire in Mark Twain National Forest, been camping more times than I can remember, and once been stuck up to the doors in mud on a back-country road.

So you can imagine my dismay upon learning it had developed a small oil leak. This weekend a friend stopped by to help and we used a little spray cleaner to remove the grime so we could better identify the leak, and tighten up the bolts holding the valve cover down. But, the next time I tried to start it, it wouldn't work. Opening up the hood, and cleaning the electrical connectors in the area we had hosed down got me on my way, but less than a mile later, the engine died, perhaps for the first and last time. Attempting to start only gave an oscillating choofing-chunking noise, along with a blinking check-engine light.

Times have changed. My belongings now include a small building, and I find my wanderlust has waned. Eventually, it will be time to select a newer, smaller car. Probably time soon to start looking and at least be aware of what's available. Hopefully, this one will last long enough for two improvements to make it to my next car - I want to to have an optional ability for self-driving, and I want the NHTSA to mandate and enforce a reasonable set of security standards for connected vehicles, as well as a general improvement in the quality and security of vehicular software.

Anyhow, today after work we popped the hood, cleaned the connectors one more time, and this time noticed what one of them ran to - it was a ground line connecting the frame to the intake manifold. The nut on the manifold, previously slightly loose but baked in place with grime, and now freed, had come loose. The vibration of the starting engine caused it to intermittently connect and disconnect. After tightening that up, and cleaning the battery contacts for good measure, the car is running just fine.

AntennaCraft Television Antenna Teardown

Written 2015-08-29

Tags:Teardown Television Amplifier Antenna Analog 

A Short Story

Several RadioShack stores were closing earlier this year. One store had paper tokens describing an antenna, on sale for about ten dollars, that could be purchased by taking the paper token to the cash register. After purchasing, the cashier would exchange the token for the antenna. Once the cashier returned from the back, I came to realize this antenna is massive, nearly two feet in diameter, and not something that would sit nicely behind my television. But, all sales are final at a store closing sale.


The antenna comes in a large, flat box. Inside you will find the antenna, a short run of 75 ohm coax, a DC wall adapter, and a power injector.

TV antenna on sale from RadioShack TV antenna on sale from RadioShack

Inside the Antenna

Twelve plastic-tapped screws hold the front and back of the antenna togther. Some of the screws also hold antenna elements together, which makes reassembly take a big of alignment. At this stage, removing the nut from the coax port is not required. The antenna elements almost appear to form a quad-helix, even though each elements is a bubble-lettered T.

TV antenna on sale from RadioShack TV antenna on sale from RadioShack TV antenna on sale from RadioShack

RF Amplifier

To remove the RF amplifier, the coax port nut most first be removed. This single PCB is responsible for wideband amplification. Power is supplied through the coax by a DC wall brick and power injector, runs the amplifier which pushes the boosted RF down the cable, and then past the power injector towards the television. Additionally, the unpopulated 5-pin port appears to support unbalanced coax to unbalanced coax amplification, although this configuration feeds in the balanced antenna directly.

TV antenna on sale from RadioShack TV antenna on sale from RadioShack

BMA Analog Access Control Card

Written 2015-08-27

Tags:AccessControl RFID Card Analog 

Some place in town used to use these access cards. Eventually, some cards and readers made it from the people decomissioning the office to the hackerspace. When the hackerspace moved, it was being thrown out and ended up in my car. Two moves later, I suspect these cards are the only thing left, and on the way to being tossed out of the garage, I take them apart.

2015-08-27_09-13-09 2015-08-27_09-13-31 2015-08-27_09-13-48

These cards have four filters or capacitors connecting different coils of wire. There do not appear to be any digital components, so I suspect these badges either all act like a shared key, or else the combination of filters encodes a pattern of frequencies that is unique to the card.

Ethanol is Free

Written 2015-08-17

Tags:Nebraska Gasoline Ethanol 

This weekend, while traveling through Nebraska, I found an interesting anomaly. At a Caseys filling station, both E10($2.60/gallon) and standard($3.00/gallon) were available. E10 is a blend of 10% ethanol with 90% gasoline. While calculating the cost of ethanol(denoted e) by removing the cost of gasoline(denoted g) from E10, an interesting thing happens. We can model the costs like so:

  • g = 3.00
  • .10 * e + .90 * g = 2.60
Solving for e
  • .10 * e + 2.70 = 2.60
  • .10 * e = -.10
  • e = -1.00
This means that the ethanol in E10 must cost about $-1.00/gallon compared to standard gasoline.

Taking Apart the Honeywell Thermostat

Written 2015-04-27

Tags:KCPL Honeywell Atmel Atmega 

I have a thermostat

It was made by Honeywell, and it came with my house. It is also in daily service without a hot spare, so I have been waiting since last fall to do this teardown.

What is an energy optimizer?

My electricity provider offers a sweet deal where they give you a free programmable thermostat, in exchange for their gentle adjustment of your temperature during peak usage. This implies some sort of communication link between my house and their systems.

What is inside?

One assembled thermostat, front

Honeywell Thermostat Teardown

One assembled thermostat, back

Honeywell Thermostat Teardown

We can see three subsection of the device. In the center is the umbilical to the home. On the left is a small antenna. The rest of the PCB is covered by the frame.

What is under panel number one?

Honeywell Thermostat Teardown

Under a pair of plastic clips we find a small PCB fitted to the main PCB

What could it be?

Honeywell Thermostat Teardown

Interestingly, this appears to be the radio section of the device. We find

  • at least four crystals or oscillators
  • a seemingly unused 10 pin header, possibly for initial programming
  • ST M24256 EEPROM
  • LTWC455E six-element ceramic filter
  • CDBC C28 ceramic discriminator
  • 4 pin header going to the main PCB
  • USB mini connector although it is not routed for USB
  • ta31149 FSK detector
With the above parts list, this has got to be our radio.

Where does it go?

Honeywell Thermostat Teardown

Simple enough.

Seven more clips to go

Honeywell Thermostat Teardown

Five clips hold the front bezel on.

Last two clips unclipped

Honeywell Thermostat Teardown

Here is the full rear PCB

Anything under the LCD?

Honeywell Thermostat Teardown

No, not really, just a light-spreader.

Back of the LCD

Will it run without the radio?


Yes, yes it does.

What is next?

Next would definitely be tracing out the connectors on the radio PCB. Honeywell also makes a WiFi version of this unit, which I suspect is the same but with a different radio PCB. The four-pin connector appears to carry power and ground, leaving two signals for a data bus.