Like many buildings, the building we live in has a panel at the main entrance which allows guests to call their hosts. The guest initiates the call by looking up and dialing a apartment specific buzzer code, and the host can remotely unlock the front door by dialing 9 on their phone.
Occasionally, we’ve had the need for an extra set of keys when guests are visiting. Given the ubiquity of smart phones, I’ve thought: Wouldn’t it be great to build a web interface which would essentially pick up the phone and dial 9, permitting entrance to the building without a set of keys?
The easiest way to do this was to write an application that uses an analog modem, which can detect a ring, pick up the phone, and generate tones. Finding a suitable modem was the hardest part, given that there are so few applications for analog modems since the widespread use of broadband Internet in the late 1990s. Further complicating things was I was looking to use a Raspberry Pi – this meant I needed a modem with a USB interface that works with Linux. From my research, the TRENDnet TFM-561U modem seemed to be the best fit for this purpose – testing has since confirmed it works great.
I wrote the application itself in NodeJS. Using the administrative page (behind a firewall) the Host sets up a password, has the option of adding a note, and must set dates for when the password starts and stops working. Note that there’s no login – it’s hard enough to remember a password, let alone the corresponding login. The passwords are stored hashed (using bcrypt) – it’s assumed that there are very few logins setup, so when the guest logs in, the password they enter is compared against the hash of every password in the system.
The Internet facing, or guest page, is simply a passphrase box. When a guest enters a correct password, the system will wait for a “ring” (for up to 5 minutes by default). The guest can then dial the buzzer code. When the modem detects the ring from the main entrance, the application will instruct it to answer the phone, dial 9, and hang up. The building’s entry system will then unlock the door, permitting the guest to enter.
I’ve only tested with my primary PC (Ubuntu Linux / Intel x86)
Get the code! You can download from GitHub, or clone the repository https://github.com/raudette/lockandkey.git
Install Node and the required modules. In an Ubuntu Linux environment, this can be done as follows: sudo apt-get install nodejs sudo npm install express sqlite3 bcrypt-nodejs node-validator fs body-parser serialport
You may also want to look at the PM2 process manager for Node – it makes it really easy to automatically start Node applications on boot up, and a dynamic DNS service such as the one provided by dyn.com to access your
Review the lockandkeyconfig.json configuration file.
port: The port used by the public web interface (configure your router to expose this port to the Internet)
adminport: The port used by the administrative interface. This is used to configure accounts
unlocktimeout: Length of time, following a successful login, for which the system will pick up the phone and dial 9.
modemmanufacturerstring: The string used to identify the modem which should be used by the application. Use the Linux dmesg command after plugging in a USB modem to see the manufacture string associated with your device. Use Conexant for the TRENDnet TFM-561U.
You can start the program by running node lockandkey.js
With the default values, to setup accounts, you can access the administrative interface at: http://localhost:3001/
and the door opening interface at: http://localhost:3000/
I can see this particular project being useful to others – let me know if you have any suggestions. For example, let me know if there is interest in a Raspberry Pi SD card image, a simple phone Android/iPhone app to avoid book marking the website, improvements to security, mandatory HTTPS, or eliminating the need for a dynamic DNS service in a home environment.
Update – March 27, 2017
One of my friends needed a solution to provide his clients with access to a condo unit he is renting over Airbnb. He’s now using this solution, which is running on a Raspberry Pi.
About 15 years ago, a friend of mine informed me that Sensirion would send a sample of one of their temperature sensors to anyone who filled a form on their web page (I’m not sure if this is still the case). After the Sensirion sensor arrived in the mail, I wired it to my PC’s parallel printer port, wrote a little code, and built a simple web page that could display the room temperature.
Ever since then, building my own weather station has been on my hobby-project back log. I realize one can purchase all sorts of thermometers and weather stations off the shelf, but I thought it would be fun to build my own.
I decided I wanted a wireless station with a web front end, which would measure and log temperature, humidity, barometric pressure, and the soil moisture of my plants.
I decided this would be a good project to learn about development with the NodeJS runtime. I was pleased – not only was it easy to learn, but it was easy to do what I wanted.
The weather station itself is built around the Arduino platform, which collects data from various sensors, and sends an update every 15 minutes using a wireless module, to my PC, equipped with a matching wireless module, connected by USB (it is not using Wi-Fi).
A) Soil Moisture Sensor
B) Battery Pack (I use 3xAA batteries)
C) DHT22 Temperature and Humidity Sensor
D) BMP180 Barometric Pressure Sensor
E) APC220 Wireless Module
F) Bare Bones Arduino (Atmel 328P Microcontroller)
On my home PC, I have a client application that listens for the broadcasts from the weather station. When a reading is received, it makes a web service call to upload the weather readings to a server I have hosted on Amazon EC2.
The biggest challenge I encountered was power consumption. My first revision consumed 60 mA, and drained 8 AA Alkaline batteries in a little over a day. I have since been able to reduce the average power consumption to about 1 mA, and have been running on 3 AA batteries for quite some time.
To achieve this, first, I incorporated the Narcoleptic sleep library for the Arduino, and sampled the temperature once every 15 minute, which saved about 12 mA. Turning off the the wireless module when not in use saved about 8 mA. The voltage regulator I was using to reduce my 12 V battery pack to 5V consumed 14 mA – simply moving to 3 AA batteries allowed me to eliminate it. The final savings came from moving the circuit from an Arduino Nano clone to a bare-bones Arduino, which eliminated the draw from the Nano’s LEDs, voltage regulator, and USB-to-serial converter.
From my website, I can then view the readings and compare my readings with those from Yahoo Weather.
I stumbled on an interesting article, Copyright quirk leaves James Bond up for grabs in Canada, in the Globe and Mail the other day. In Canada, copyright expires 50 years after an author’s death. Ian Fleming died in 1964, which means his James Bond series of novels have become a part of the public domain in Canada.
Copyright is granted to allow content creators to receive compensation for their work, providing an incentive to create original work. Many (myself included) would argue that 50 years of protection is ample – if I died tomorrow, my children, and their children, would directly benefit from any royalties collected from my work though my estate.
At some point, society receives a greater benefit from having the work enter the public domain, where anyone can read and re-print the text, and re-use the characters and story lines. I, for one, have enjoyed the BBC’s contemporary take on Sherlock Holmes, made possible by the characters in the public domain.
In Canada, one can now create their own modern take on the James Bond character and novels, without getting permission or paying royalties to the rights holders (note that this does not include the movies).
The Bond books themselves can now be redistributed freely in Canada. Project Gutenberg is an organization that digitizes and distributes public domain texts – the works of Mark Twain, Jane Austen, and Sir Arther Conan Doyle are all available. The Canadian branch of the site, Gutenberg.ca, has already taken advantage of our life+50 copyright and posted a copy of Ian Fleming’s Goldfinger.
A part of me wants to buy Fleming’s books, scan them, and post them on a Canadian web site while I still can – unfortunately, this site is hosted in the US, so you won’t see them here.
I found a design for a Diesel engine on Thingiverse by Nick Randall – I decided that his trucks and wheels would make an excellent base for my train, as he had a tested design with the right dimensions.
The Toronto Public Library has a 2 hour limit on 3D print jobs. To work within this limitation, I printed the design at low resolution over three sessions. The body was printed in two sessions, and glued together with Krazy Glue (cyanoacrylate). In one of the sessions, a different filament was used. The final toy was painted and assembled with screws.
I learned a few more things about 3D printing, design in general, and sharing online.
Parts printed with PLA material can be glued together with Krazy Glue
In this instance, there is a visible gap. The parts were printed with different filament, and as a result, the parts didn’t align exactly. The output from one of the print jobs warped. When laid flat, the middle was probably 2 to 3 mm above the surface
As would be expected, detail is lost when printing at low resolution
When designing a model for printing on 3D printers, the limitation of not being able to print in mid-air must be considered. Although printing with supports is a solution, it leaves a less-than-perfect surface. It would be interesting to learn how more experienced designers work around this issue. It would also be interesting to try a 3D printer capable of using a dissolvable support filament.
A model printed with PLA can be painted with Testor’s Enamel
The library is a great place to learn about 3D printing, and print small parts. It is less expensive than other places – a two hour print job costs about $6. For my next project, however, I would probably look at other alternatives without these limitations. I think the library has probably achieved a good compromise, making a technology available to anyone with interest to learn and a library card, but definitely not offering a service which would compete with commercial offerings.
When I thought about 3D printing, I though about the physical realization of an object. In reality, there are many things that must be considered when designing anything physical, and 3D printing is not the solution to all of them. This is evident even in the simplest of designs, such as this one, where metal screws are used to fasten parts and enable movement.
This model was designed to scale – this might be appropriate for a scale model, but the train looks very long relative to the other wooden trains on the track. Many of the features, such as the lights, windows, and doors, are very small. If I were to design another toy train, I would exaggerate features, and would not design to scale. George’s Trains, a local model rail hobby store, apparently stocks a wooden subway train that follows these principles and appears to be a much better toy.
Finally, it has been fun posting and sharing my designs on Thingiverse. Although I have accounts on other sites with social-network type features, this is the first time I’ve posted anything. It is fun to have an forum to share my work, and it’s great feeling to see that people have looked at my design and clicked “like” – recognition for someone having fun with basic skills, practising a hobby.
I haven’t worked in 3D at all before, and I was looking for a simple project.
As with the Brio/Duplo wagon, I was thinking about what was within my ability, and not commercially available. I decided I would try to build a custom tire valve stem cap with my daughters’ school logo (a polar bear).
Looking at freely available 3D modelling tools, I checked out Blender and OpenSCAD. OpenSCAD seemed to be simple for someone starting out with designs built out of basic shapes.
I converted the bitmap logo I had to a vector drawing using Inkscape‘s “Trace Bitmap” feature. Following an Instructables tutorial, I exported the bear’s outline and features to a DXF file, which can be imported into OpenSCAD. I encountered number of difficulties (it has been a while since I completed the design – I can’t remember which issues, specifically, I encountered). I tried again, with great results, using the Inkscape OpenSCAD export plug-in.
I merged the bear with a cap designed by Dan Ujvari, and printed it at the Toronto Public Library’s innovation lab. I used a black permanent marker to highlight the bear’s details after printing.
It was interesting to learn that even with a simple project as this one, there are limitations to 3D printing. It was almost impossible to remove the support material on the reverse side, as the bear is narrower than the cap. If I were to refine the design, I would make the bear the same width as the cap. I definitely have more to learn about successfully designing an object around the limitations of current 3D printers.
I have been excited about the potential for 3D printing for quite some time.
Shortly after our local library acquired a couple 3D printers, I took the mandatory course, where we were taught the two primary rules of printing at the library:
Rule #1) Don’t touch the heating element
Rule #2) Don’t print guns
Course completed, I started to think about applications. What can’t you just buy, what makes sense to print?
The idea of combining Duplo and Brio seemed like a great idea – I was thinking of an elaborate track with bridges over bridges, and Duplo seemed almost perfect for the job. What I really wanted was a piece with a wooden train (Brio) top, and Duplo bottom.
A quick search revealed that I wasn’t the first person to think about this, someone had already designed a Duplo/Brio bridge support system. Looking into this further, and loading these parts into 3D printing software revealed that each segment would take about 2 hours to print – the maximum time allowed on the library’s printer. Given that a simple bridge would require at least four segments, I looked for alternate ideas and stumbled across the Duplo/Brio wagon.
I downloaded the file, went to the library, and printed it out. 83 minutes later, my train was completed. I attached the wheels to the body with paper clips, and glued fridge magnets to the ends for the couplings. I was quite pleased with the end product (see photo). The library charged just under $5 for the printing time, which is about what a train car costs from a local toy store.
Taking this idea further, I thought I may try to design my own toy 3D printed TTC subway or street car for wooden train tracks. I have occasionally seen them available commercially, but they are generally hard to come by.
My personal brain dump, Opinions, Projects, Toronto