The Golden Records

In 1977 NASA launched the Voyager 1 and Voyager 2 space probes to study the outer solar system. Voyager 1 flew by Jupiter, Saturn, and Saturn’s largest moon, Titan. Voyager 2 flew by Jupiter, Saturn, Uranus, and Neptune. After 37 years the probes continue to send data back to Earth as they hurtle out of the solar system.

Each probe contains a gold-plated copper record encoded with images and audio from our planet. It’s fascinating to see the list of sounds that people thought were important enough to use as an interplanetary greeting. It’s like a greatest hits album for our entire planet: birds, the ocean, Chuck Berry, Mozart, a tractor.

The easiest way to listen is probably YouTube. There’s also and another option, but I find the YouTube playlist navigation to be easier.

More information here and here.

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Let’s learn about furnaces!

When we moved in to our new place our furnace wasn’t quite working. We didn’t notice it at first. It would turn on for a few minutes and sounded normal, but then it would turn off before reaching the temperature set on the thermostat. This is known as “short-cycling.”

Our furnace

Our furnace is a Gibson GL1RA 045N-08A. It’s a basic single-stage, non-condensing, natural gas, forced air furnace. The control board dictates the run sequence, which is something like this:

  1. Thermostat indicates that the heater should run.
  2. Draft inducer blower begins running to move air past the burners, through the heat exchanger, and out the exhaust flue.
  3. 30 seconds later the hot surface ignitor starts.
  4. 30 seconds to a minute later the gas valve opens and the burners ignite. The hot surface ignitor is depowered. Exhaust gases flow through the heat exchanger and out the exhaust pipe. The “burners,” by the way, are just pieces of metal that guide the gas and flame into the heat exchanger
  5. A short time later the main furnace blower turns on and begins moving air past the heat exchanger and into the house.

Due to the inherent danger of fire and explosive gas, modern furnaces include many safety sensors. If something is amiss the furnace errs on the side of caution and shuts itself off.

If the draft inducer blower isn’t able to move enough air (maybe a bird built a nest in the exhaust flue), a pressure switch detects this and shuts the furnace off. Because if hot gasses can’t exhaust properly the furnace could overheat. Or carbon monoxide could flow into the house.

The flame in a furnace is designed to follow a defined path: through the burner and straight into the heat exchanger. Flame rollout switches detect if a flame exists outside of this defined path and shut the furnace off.

Our issue #1: Flame sensor

The flame sensor is another important safety feature. As you can probably guess, it detects the presence of a flame. If there is no flame then the gas will be turned off within a few seconds.

Furnace flame sensor
This is what it looks like! Please excuse my scaly climber hand.

The flame sensor is nothing more than a small metal rod. It mounts through a sheet of metal via an insulating ceramic bracket. The non-flame end of the sensor connects to the furnace circuit board.

It’s pretty insane how flame sensors work. From what I’ve been able to learn, it sounds like the control board applies an AC current to the flame sensor and electrons flow from the sensor through the flame to ground at the base of the flame, thus creating a measurable current. It’s called “flame rectification,” if you want to read more about it. The current is only milliamps but it’s enough to be detectable.

To work correctly the flame sensor must be clean. Apparently these things can accumulate enough residue over time that they become unable to reliably conduct the small current from the flame. That wasn’t our problem. Sometimes the heat from the furnace can cause the ceramic mounting bracket to crack thus causing the flame sensor to touch ground and short circuit, which makes it unable to detect the flame. Our flame sensor was grounding out, but this wasn’t the reason.

No, our problem was more unique. Each port in the heat exchanger contains a metal rod called a “baffle” that is apparently supposed to improve heat dissipation. One of the baffles was sticking out of the heat exchanger and pushing against the flame sensor. I have no idea how something like this happens. The baffle was not being held in place by the metal retaining wire. Probably a careless error during a routine servicing.

Furnace heat exchanger baffles
The baffle in the middle is great—it’s not sticking out and the retaining clip is holding it in place properly. The baffle on the left is bad—it’s sticking out and the retaining clip isn’t doing a damn thing. The flame sensor would normally hang down just in front of the left baffle.

Our issue #2: Over-temperature limit switch

And the final as yet unmentioned safety sensor is the over-temperature limit switch. Furnaces are built to withstand specific maximum temperatures. The over-temperature limit switch is suspended in the air around the heat exchanger. If this air becomes too hot it might shorten the lifespan of the furnace. There are a number of possible causes:

  • Lack of airflow. Maybe the air filters are dirty or the homeowner closed all their vents or the blower motor is dead or dying.
  • Gas flow is too great. This is referred to as “over-firing.” It causes too much heat to be created.
  • A hole in the heat exchanger. This is bad as it means carbon monoxide is being expelled into the house.
  • And one final possibility: The temperature sensor is bad. This was the case for us. Replacing was fairly easy… just had to disassemble and reassemble a few chunks.

Cost to fix?

$160 for an HVAC guy to not quite fix the flame sensor problem, $30ish for a replacement flame sensor that I didn’t need, $20 for the replacement temperature switch, $6 for a roll of gas pipe teflon tape, and the biggest cost of all: About 50 hours of my time researching how furnaces work, watching many many YouTube videos about furnaces, finding and visiting a furnace parts store in SF, calling the HVAC guy, meeting him and discussing the problem, and of course writing this blog post.

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I got a new bike!

Nothing special, just a cheap bike for commuting to and from the train station. I got one of the cheapest ones I could find that I’d be happy with: a Retrospec Mantra. Black frame, red wheels, pink seat and handlebar grips. 57 cm. 26 lbs.

Retrospec Mantra

It’s a single speed with a flip flop hub, so it can be ridden as either fixed gear or freewheel. I tried riding fixed gear for a week and I didn’t like it. I like being able to coast so I can easily position my pedals where I want them at stop lights or when maneuvering. So I switched it to freewheel.

It’s been ok so far. No complaints. I mildly wish I had a few gears to make it easier to start pedaling again after stopping at stop lights and stop signs, but it’s not important enough to change so long as my commute remains flat.

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My old bike was stolen :-(

My 2003 Fuji Silhouette was stolen in mid-October. This is the bike I’d ridden 11,000 miles on. Across North Carolina. From San Jose to Los Angeles. This one:

Day 2 - Between Santa Cruz and Carmel

The Story

I had biked to the Sunnyvale Caltrain station around 7:50am. I locked the bike to the bike rack with a cable lock similar to this one. I hopped on the train to San Francisco for work. I returned around 7:20pm and the bike was gone. I’d been doing this for about a month. I had applied to rent a bike locker from Caltrain but I hadn’t received a key yet (they’re slow—it took them a month). I knew u-locks were preferred, but I was hoping my existing cable lock would suffice until I had a bike locker.

I was extremely annoyed. The bike was 11 years old, was in desperate need of a tune-up, and worth maybe only $50, but it is mine. I hate crime and I had criminals. It is not ok to take something that belongs to someone else. I wasted a lot of my time filing a police report, listing the bike as stolen on various web sites, looking for it on craigslist and eBay, researching a new bike, researching bike locks, researching bike lights, assembling a bike, attaching fenders and lights, and generally being angry.


If you’re thinking about buying a second-hand bike, always check the bike’s serial number against online stolen bike databases. These two seem popular: and

You can find the serial number stamped into the metal on the bottom bracket (where the pedals attach). Which brings me to my other point…

Bike manufacturers: Please make sure your serial numbers are easy to read! From what I’ve seen they’re generally a pain in the ass to decipher. Poorly etched. Small. Ambiguous O or 0. It’s doesn’t have to be this way! More clear serial numbers can reduce incorrect transcription and improve bike recovery. I’d be happy if serial numbers were embossed in a huge font across the top tube. Unattractive, you say? Functional, I say. And functional is attractive.

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San Diego Zoo and Safari Park

Earlier this year Emily and I flew to San Diego for Gabe and Korianne’s baby shower in Dana Point. We stayed in downtown San Diego. It was fun! I like San Diego.

While we were there we visited both the San Diego Zoo and the San Diego Zoo Safari Park. The zoo is located in Balboa Park, which is a large park in the heart of the city. The safari park is a 40 minute drive away, in Escondito. We went on a Caravan Safari, which was expensive but I liked it and thought it was worth it.

We also stopped by Point Loma before leaving.

You can see all our pictures on Flickr. A few of my favorites are below.


Emily and me feeding a Giraffe

Old Point Loma Lighthouse

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Sennheiser HD 280 Pro vs Audio-Technica ATH-M50 headphones

I’d been using Sennheiser HD 280 Pro headphones since November 2007. They’re great and I’ve been happy with them. They’re popular headphones—I believe they’re one of the standard headphone choices at both Facebook and Google. Last month the plastic headband on mine broke in half and they were no longer wearable. I figured I’d try something new.

Based on Amazon reviews I purchased a pair of Audio-Technica ATH-M50 headphones. I’ve used them for a week now and I prefer them to the HD 280 headphones. They’re both great and you really can’t go wrong with either choice, but I like everything about the ATH-M50 headphones just a bit more.

The biggest reason I prefer the ATH-M50 headphones is that the sound feels warmer. Low range sounds are fuller and more pleasant. Imagine someone playing an upright bass a few feet away. That’s a very full sound that’s difficult to recreate with headphones. I think the ATH-M50 headphones do a better job without the bass being excessive or overpowering.

Wearing any headphones for a long period of time eventually makes my eardrums tired. I’m able to wear the ATH-M50 headphones for longer before that happens.

They both block out a similar level of ambient noise. I feel like the ATH-M50 headphones attenuate mid and high range environmental noise more, which means background conversations are harder to hear which I appreciate because it allows me to stay focused because voices are distracting.

I also find the ATH-M50 headphones to be more comfortable. The ear cups feel more appropriately sized for my ears (bigger? smaller? more square? not sure). The clamping force doesn’t feel too tight. Maybe my head is big, but I felt like the HD 280 headphones clamped too tightly.

I also prefer the build quality of the Audio-Technica headband: the padding is sewn to the headband and not replaceable. It’s solid yet soft. Whereas the padding on the HD 280 headphones is removable, replaceable, and always felt a little flimsy to me. In fact, the padding on mine had been slowly tearing and twisting for years.

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My Headphone Preferences

I wear headphones a lot at work. Specifically for three or four hours a day, five days a week, for the past 8 years.

I prefer headphones rather than earbuds. I find earbuds to be uncomfortable for long periods of time. Headphones are easier to slip off and on, which is important because I want people to feel like they’re not bothering me when interrupting me to talk. Also earbuds get gross and slimy.

I prefer circumaural (“over-the-ear”) instead of supra-aural (“on-the-ear”). My ears get sore from supra-aural headphones pressing my ears against my head.

I prefer closed-back instead of open-back for two related reasons. Closed-back headphones don’t leak as much audio into my surroundings, which means I don’t bother my co-workers (I hope). It also means they block out a fair amount of ambient noise, which allows me to listen at a lower volume which allows me to worry less about hearing damage due to having speakers next to my head for many hours. They don’t block out as much ambient noise as well-fitting earbuds, but I’m ok with that.

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Europe 2013, Part 3: Spain


You can see all 90 pictures from Barcelona or the best 10 (mixed with the best pictures from elsewhere on our trip).

After watching stage 8 of the Tour de France, we drove back to Barcelona and picked up the keys from our Airbnb host. The place was OK. It would have been great, except the floor was filthy. No matter—we were located on Plaça Reial, close to La Rambla and close to a subway station.

La Sagrada Família I’ve always liked Barcelona. It’s a fun city. Easy to get around by foot, subway, or taxi. The Gaudí architecture is great. I recommend going in La Sagrada Família—I thought the inside was cooler than the outside. Casa Batlló and Park Güell are also neat, but not required if you find architecture and design boring.

We saw a fantastic flamenco show at Palau de la Música Catalana. We bought our tickets in California before we left and the only seating options were far back or front row. We opted for front row. It was a little awkward, but also a little totally friggen sweet. The dancers were intense, especially the women. Fierce, piercing, angry. The tickets were $100 each and absolutely worth it.

Our only notable meal was at Bodega La Palma. It was great and I recommend it. Creative and delicious food, a friendly and accommodating waiter, and a shitload of wine—we had a great nap after this.

A word of caution: Thieves and pickpockets run rampant in Barcelona. We saw a thief grab a mobile phone from a table and run down an alley. Don’t leave valuables sitting on your table in big cities!

Madrid and Toledo

You can see all 50 pictures from Madrid and Toledo or the best 9 (mixed with the best pictures from elsewhere on our trip). Also check out this photosphere of Plaza Mayor in Madrid.

From Barcelona we took high speed rail to Madrid. It’s 380 miles and would have taken 5.5 hours by car, but takes only 3 by train. Our speed topped out around 300 km/h. We bought the tickets minutes before boarding and they were pricey, €110 each. They would have been half that if we had purchased in advance.

The landscape between Barcelona and Madrid is less interesting than Italy, Japan, Slovenia, or really anywhere else—scattered farms, scrappy big grasses, desert shrubs, and rolling rocky sandy hills. A bit like California, actually.

We stayed at Hotel Moderno, which is in a great location. Immediately next to Plaza Del Sol and a few hundred yards from Plaza Mayor de Madrid. We dropped our bags in the room then grabbed lunch outside.

Emily at the Plaza de Oriente at the Royal Palace of Madrid

After lunch we walked half a mile to the Royal Palace of Madrid, which is totally sweet. It’s a large palace typical of 18th century Europe. Ornate and extravagant. I loved the expansive Plaza de la Armería Courtyard on the south side.

Royal Palace of Madrid

The next day we took a short train ride to Toledo. It’s a walled city on a hill partially surrounded by a river. The city has been known for making bladed steel weapons since 500 BC, and knives and swords are common in gift shops.

The Toledo Cathedral is awesome. So old! Intimidating, big, detailed, precise.


You can see all 55 pictures from Sevilla or the best 6 (mixed with the best pictures from elsewhere on our trip).

The last stop on our trip was Seville, in southern Spain close to the Mediterranean coast. We stayed at El Rey Moro Hotel Boutique and loved it. It’s in a part of town with narrow, winding, cobblestone streets. The building has a lot of character and the rooms are all unique.

Plaza de España, the Alcázar and Cathedral of Saint Mary of the See are all really cool. We had a few good meals along Calle Mateos Gago, near the cathedral.

Plaza de España

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