Category Archives: Miscellaneous

Netflix on iPad/iPhone does not work when connected to a router running DD-WRT [Fix]

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I was pretty frustrated when I realized that for firing up my new iPad I needed to install iTunes to my desktop. On top of that, I needed to add a credit card number to download a free application from the App Store. I worked it around by generating a one-time number from citicards.

I decided to install Netflix and did not work, even tried resintalling and changing SSIDs. The only way to make it work was by using a backup SSID from the U-Verse router.

After researching I found out that the DNSMasq package from DD-WRT thinks that the connection from Netflix on the iPad looks like a DNS Rebinding attack.

There are a couple of workarounds:

  1. Use a different DNS server in the iPad/iPhone wireless configuration, like the one provided by OpenDNS: 208.67.222.222
  2. Add a startup rule to DD-WRT to stop DNS rebinding:
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killall dnsmasq
sed -i -e 's/^stop-dns-rebinding/#&/' /tmp/dnsmasq.conf
dnsmasq --conf-file=/tmp/dnsmasq.conf

I pursued the second workaround as it allowed me to keep the wireless connection “stock”. Netflix is now working properly on my iPad.

Stop DNS rebinding

Stop DNS rebinding

Solving the Garage Door Opener Safety Sensor Problem [DIY]

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What I expected to be a 15 minute fix became to be an almost 2 hour one. The main reason: the problem was not really related to the safety sensors, but a bad cable which I could not identify the first time. But it was worth changing them anyways as the original safety sensors were really worn out and not installed properly using any brackets at all. This was against code and was like it since I bought the house.

I proceeded to install the new safety sensors, and after ensuring that they were working properly. I installed the brackets 17 inches above the floor. Aligned the sensors and worked perfectly until I faced a new problem.

The garage door has thick horizontal wood bars which were wider than the distance provided by the brackets for installing the safety sensors. It was causing the door to open right when the first wood bar crossed the sensors. This was a big deal as it was not allowing the system to work properly. Seems  the reason why the previous owner never installed the brackets in first place.

What I ended up doing was reversing the sensors so they face backwards instead. That was the only way to make them work. This garage door opener system was installed 7 years after the house was built, so my guess is that the wrong model was chosen.

There is always a workaround. The system is working properly now.

Reversing the sensor so it does get blocked by the wood bar.
Screwing in the receiving safety sensor. Notice it is the correct location.
Screwing in the safety sensor. Notice it is the correct location.
Screwing in the safety sensor. Notice it is the correct location.
Checking distance after installation
Measuring distance from the floor to install the brackets
Brackets
Connecting cables
Cutting and pealing the cable
Provided hardware and scissors
New safety sensor
Connecting second pair of cables
Connecting cables
Main system safety sensor connectors. Here I tested the new sensors.
Cable problem – different angle
Cable problem

Garage door opener safety sensor problem [DIY]

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I had a problem today with my garage door opener. When I pressed the button to close it was not doing so and flashing the light bulbs instead.

The first thing I thought was something was blocking the safety sensors. Checked and nothing was blocking them. Next thing I though was that they were dirty. Cleaned them and nothing happened. Third thing I thought was that they were misaligned. I proceeded to realign them and even put them at a distance of 12 inches and nothing happened.

With those tests performed, I went ahead and researched on the web for possible issues.

I found this article explaining about the flashing LED & count for the led above the learning button:

Number of Flashes Problem Auto Reset Manual Reset
1 Photo-Cell totally misaligned or Photo-Cell wire open X
2 Photo-Cell wire shorted or the wire is reversed on the terminals X
3 Wall button (panel) wire is shorted in wall or attic X
4 Photo-Cell sensor sightly misaligned (dim or flashing LED on sensor) X
5 Possible RPM sensor failure or motor overheated, unplug opener to reset unit X
6 Motor circuit failure, replace main logic board X
Rapid Flashing This is not a problem but just an indicated that the opener is receiving a signal but it will not respond to an unauthorized code

Mine was flashing once, but one of the sensors was flashing intermittently. Every now and then it will be flashing 4 times too. So this test was inconsistent.

I searched again and found this article that pointed out:

11. Door does not close, light on garage door opener flashing:

  • Check The Protector System. Both sensors must be aligned or aimed across the door opening without any beam obstruction. Remove any obstruction or align both sensors.
  • Check for spider webs and/or dirty lenses. Wipe clean.
  • Make sure both LED lights are solid on each sensor housing.
  • Check safety sensor wiring and connections to the power head unit. Repair as necessary.
  • Check for diagnostic flashing code “1”. Located at the power head unit.
  • Try replacing safety sensors. Retest.

I have opted for the last recourse. To replace the safety sensors and retest.

Fortunately amazon has them in stock and taking advantage of amazon prime I should receive them in 2 days.

Will post an update once replaced. Wish me good luck.

Liftmaster 41A5034 Garage Door Opener Safety Beam Kit

Liftmaster 41A5034 Garage Door Opener Safety Beam Kit

Maintaining Passwords. What do I do?

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It comes with no surprise to me that online database of passwords are being hacked. Last week Gawker Media got compromised and their password database stolen. Passwords were stored in an encrypted format but are still prone to dictionary attacks.

So how do I do it?

I use a different password for every account I create online. I combine uppercase, lowercase, numbers and non-alphabetical characters when possible.

How do I keep up with different passwords?

Well with so many passwords it is almost impossible for me to remember them. I use an excellent software: KeePass.

Do I create my own Passwords?

I do mostly. But lately I have let KeePass generate them for me.

How do I access my own password database from different places?

The easy way? Storing the password database on a USB thumb drive. Just make sure that the database has a strong password for accessing it.

The convenient way? Synchronizing to the cloud. I use DropBox for that matter. I can download from the website, or if feasible, install the DropBox and KeePass application on the local machine where I am working on.

KeePass Password Safe

KeePass Password Safe

What If I need to access the site using my SmartPhone?

No problem. I installed DropBox and KeePass for Android. Both Applications are available for pretty much all mobile platforms.

Is my smartphone saving passwords for websites?

Yes, for convenience, although it is a security concern.

What if my phone gets lost/stolen?

I installed Android Protector and the most sensitive applications require a PIN to access it. I have also installed Lookout for Android which allows me to backup sensitive data to the cloud, remote lock, remote locate and the best option, remote wipe.

Do I change my passwords?

Yes. Every 3 months at the most.

This is what I do for my passwords. How do you do it?

Business Requirements. What are those? [#TSQL2sday]

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This quick post is in reference to the T-SQL Tuesday for the Month of December of 2010, hosted by Steve Jones. The subject is “What issues have you had in interacting with the business to get your job done?”

T-SQL Tuesday, December of 2010

T-SQL Tuesday, December of 2010

Have you ever been in a situation where you were told to develop and deliver certain application because Business folks already sold it to a particular buyer, even with a preset delivery date? You are not alone. I have experienced similar ones without even knowing “What” we were supposed to deliver, less “How” to do it.

Business and Technology need to create a partnership, and communication needs to flow back and forth. This is where a very strong business analyst with technical knowledge comes into play. If business would like to have a portfolio of products of services they can sell, it needs to be communicated with the business analyst, who at the same time will ask questions to the technical team to get an idea of the feasibility and viability of the product. If there are technical questions then they can be asked to the business analyst or even directly to the business owners if required.

Technical teams cannot develop without having a solid business requirement, or a good understanding of what the business folks want. I agree that most of the times, especially with new products or services, complete business requirements are unfeasible, but the business analyst needs to write what business folks want conceptually in a technical form, pointing out relevance and priority.

Iterative development and deployment is a trend being followed by more companies nowadays. As releases get to production on a much quicker fashion it can give the opportunity to the business folks to analyze the original requirements/concepts and recommend changes. It can also build confidence with the technical team as results are being delivered in small releases but in a progressive fashion. This is key to continuously building a partnership.

My opinion is that technical teams need to understand what are they going to develop and for what purpose. Analyze and suggest the technology to be used and work with the project manager and/or business analyst in order to come up with a timeline. Interact with the business folks in order to clarify any doubts and prototype the solution before engaging into a full blown project. Approach short releases if viable and build confidence with the business team. Never be afraid to ask questions; if you do not know “what” needs to be developed rest assured that “how”, the way you will do it, is wrong.