Tag Archives: technology

Cloud computing: a blessing and a curse

Right after the DOT-COM bubble began to shrink, a new concept of computing called cloud computing gave hope to a dying breed. It boosted the profits of entirely Internet based companies like Dropbox Inc. and opened the market for new Internet based companies. The next big step for this technology is the “smart home” which also referred to as “connected home”.

Continue reading Cloud computing: a blessing and a curse

How to build a basic antenna

We use wireless devices to send and receive information without worrying about physical obstacles. In the old days, most consumer grade wireless devices such as mobile phones, routers and RC controllers came with large antennas. Today some manufactures decided to go with internal or built-in antennas. This is not always beneficial to the consumer. For example, if you have a weak signal in an area, it would be difficult to change the position of the antenna because; you do not know where is it in the casing and you may not be able to place the device in a position. The solution is to add a external antenna.

Antenna Theory

This is a very specialized area of engineering and physics. In fact, I do not think that I am qualified or educated enough to go into details on antenna theory. Likely, an experienced Engineer has posted all the details here. If you need extensive information on how antennas work, that is the best place to start.

For our purpose of building a home made antenna, we only need few details from basic physics. This is because I will introduce you to a basic antenna design.

Antenna Length

All radio equipments comes with details on specific frequencies in which the data is transmit. We can use that information to build a whip antenna (single wire). The length of the antenna itself (“the exposed wire”) depends on the frequency of the device. To calculate the length, we take the speed, c in which the wave propagate (travel) and divide that by the rated frequency of the particular device.

The formula for length (actually it is the wavelength) is, l = c/f and since most waves travels close to the speed of light in a vacuum, we can assume that c = 2.998 x 108m/s. Now we know two unknowns (frequency is taken from a published documentation of the device), we can calculate the required length. For example, if I were to build an external antenna to my Vera home automation controller with the f = 908 MHz, I would have to build an antenna that is about 33.02 cm in length. But generally we do not built at full wavelength. Instead, most antennas use either 1/2 or 1/4 of the wavelength. As long as the antenna length is within those multipliers, it will work fine.

Antenna length difference due to wavelength difference between 2.4 GHz vs 900 MHz
Antenna length difference due to wavelength difference between 2.4 GHz vs 900 MHz

If you hate calculations, search for a online calculator. Make sure you are using the right calculator because depend on the type of antenna, the information is varies.

Build it

Once you have calculated the required length, you may use a piece of coaxial cable (with the copper core) to build your antenna. Strip the outer cable (ground plane) to expose the inner core copper wire. The length of the exposed core must be the exact same length as what we calculated for our antenna length. Let’s say we want a 908 MHz antenna. Then the core wire should be exposed exactly 33.02 cm or close to that. The length of the rest of the cable will not effect your wireless signals. But longer the cable, higher the impedance hence may even weaken the signal.

There are several choices on how to connect the other end to the device’s circuit board. I recommend against soldering directly onto to the PCB. Instead, use a pigtail connector or a wire. Some PCBs come with removable antenna wires (“clip ons”). They are usually U.fl connectors. Yes you can buy them online (cheap) with all the connectors and wires attached. If your board does not have removable connectors, you can solder a wire between the board and the pigtail connector. By keeping the antenna wire itself separate from the PCB, you now have greater flexibility in future modification.

If you do have removable connections between the PCB and the antenna wire, then it is most likely a U.fl type connector. Read more about other types of connectors here.

If you are building a GSM (~ 900 MHz) antenna, order something like, SMA female straight to U.fl/IPX Pigtail cable. The other option is to take the PCB connector from an old router (regardless of wifi frequency) and use a RP-SMA connector type antenna. Note that RP-SMA is the type that comes in 99% of all WiFi routers with external antennas. However, most GSM based antennas such as ~ 900 MHz requires a SMA female connector.

Most consumer products with antennas do not come with a good ground plane connection. You can connect a wire between the antenna lead and any of the socket plates (Example of a socket plate is highlighted by B on the following image) for a good ground connection. Make sure you clean the socket plates before attaching the ground wire.

Internal view of D-Link LAN Switch.
Internal view of D-Link LAN Switch.

Special note: if you are an electronics enthusiast in Calgary, try MRO for supplies. I am not affiliated with them nor promote them. However, I was able to find most electronics parts such as ICs, resistors, transistors, antenna parts, etc over there.

Modification to extend wireless range

Consumer Electronics Design not always beneficial if it retards the primary functions of a device. The internal antennas are such a design concept that cause a lot of headaches for tech guys like me. The primary function of a antenna is to transmit a signal, capture a signal or both. Since most modern equipments are manufactured with plastic casings (as opposed to metal), a lot of manufactures have opted for internal antennas. The advantage; now nothing is sticking out, they can make the equipment more desirable to mainstream consumers by making “beautiful” equipments boxes. I am on the other hand one of those people who would buy a device for its’ practical functionality over looks.

The following modification was made on my VeraLite (Vera3 variant) to remove dead-zones in my Z-wave network. However, using the same principles and steps, you can also extend the range of your WiFi network. I will add bits of information specific to WiFi extension on this article.

Vera3 and VeraLite controllers

The door locks on Z-wave networks almost always accept only secure authenticated signals. In order to operate the locks you must send the signal either directly from your Z-wave controller (in this case VeraLite) to the locks or use repeaters (or modules with secure repeaters) that are capable of secure signal handling. I found it is extremely hard to find such repeaters in Canada.

So I went with the second option; direct communication between the locks and the controller. However, my controller is in a locked cabinet far away from the locks. This causes reliability issues because unlike Z-wave light switches, door locks cannot take unsecured signals repeated from nearby low security switches.

Modification to the controller

Warning: This modification will void your manufactures’ warranty. Beware of the static charges. Static electricity could burn out your circuit board. Either use a grounded anti-static wrist strap or use extreme caution. Remove all power supply units (batteries & DC power unit) before opening the case.

Parts, tools and technical information

  • Antenna must be able to handle frequency range of the device (for this mod, 908 MHz)
  • U.fl/IPEX to RP-SMA Pigtail with at least 5 cm; 10 cm is too much; find happy medium) of wire length between the connection points
  • GSM antenna extension cable (optional and longer the cable, more problems arises)
  • Small needle nose pliers
  • Small Phillips screwdriver and a large slotted screwdriver or a flat plastic or mental piece
  • Small electric drill or a utility knife

It is very easy to take apart VeraLite unit. Only two screws and few plastic clips that holds the plastic casing. One of my readers (“Jack”) pointed out that the screws will not come out from the casing. In that case do not try to pull it out. Once the screws are lose, you do not have to take them out of the holes in order to separate the green cover from the case. Use a flat head screw driver or a flat object to pull the cover apart. Be careful to not to break the clips that holding the two parts.

Inside you will find the internal antenna attached to side of the box with a connection wire going to the Printed Circuit Board (PCB). Click on the the image below for more detailed information.

VeraLite PCB: A = Internal antenna, B = Cutout made for ext. antenna. C = Antenna connector
Figure 1: VeraLite PCB: A = Internal antenna, B = Cutout made for ext. antenna. C = Antenna connector

Disconnect the internal antenna wire from point C (refer to above image) by gently twisting and pulling on the connector. Do not pull from the wire because it will break the wire from the connector. I recommend using a small needle nose pliers.

Make a hole through the casing, either on the back or on the side. Make sure it is large enough to pass the SMA (SubMiniature version A) male connector but not its’ neck. I used a box cutter to be safe, but you can also use an electric drill. If you are using a large construction grade drill, please be careful to not to break the box. I found the utility knife to be the best option.

Creating a circular cutout to pass the male SMA end
Figure 2: Creating a circular cutout to pass the male SMA end

Take the U.fl/IPEX to RP-SMA Pigtail (Figure 3) and connect the U.fl side to the board. Then pass the SMA side from inside to outside. Then connect the other end to the point C (Figure 1) on the board.

U.fl/IPEX to RP-SMA Pigtail
Figure 3: U.fl/IPEX to RP-SMA Pigtail

Internal and external view of the final product.
Figure 4: Internal and external view of the final product.

Put the box back together and your done! For the external antenna now you have the option of adding it directly to the device shown in Figure 3 or you can add a antenna cable before adding the antenna itself. This is what most people do when they want to secure their devices in a cabinet. You can keep the network controller inside while antenna outside for greater coverage.

It is quite possible to salvage antenna and U.fl/IPEX to RP-SMA Pigtail connection wire from old devices such as wireless routers and GSM devices. But unfortunately most WiFi routers are on 2.4 GHz band while Z-wave is in 900 MHz band. For example, this particular model is at 908 MHz frequency. If you cannot find a GSM device to get an antenna, please buy one (~ $8 – $12 CAD) to take the full advantage out of this modification. Connection wire from a WiFi router is suitable for Z-wave broadcast.

Antenna length difference due to wavelength difference between 2.4 GHz vs 900 MHz
Antenna length difference due to wavelength difference between 2.4 GHz vs 900 MHz

If you would like to know more about how antennas work, try this site.

Modify WiFi Routers

Yes, you can modify your b/g/n/ac WiFi routers with built-in antenna(s) by following the same instructions. The only difference is now you can use any old 2.4 GHz or 5 GHz (not very popular) antennas for your project.

Modules associations

There are few different companies that manufacture modules for home automation. Even with products from same company, it can be difficult to find all in one solutions to consumers’ need. Through manipulating the behaviors of the modules through the controller, we can accomplish almost anything.

Let’s look at a situation where solution is not obvious. In my home, I have a separated garage with a conventional door opener and lights. To automate the door, I added a Z-wave inline module. It works great, but it often interferes with the built-in light of the opener. So I removed the light fixture from it. Now every time I come home the garage is dark because the other set of lights requires me to turn on separately. Solution is to combine two modules; the door open/close sensor and the light switch module.

I wrote down what I would like to have and what equipment I have to solve the problem. What I wrote is; Sensor is Armed –> Sensor is Connected/Disconnected –> Turn ON lights –> Wait 10 min –> Turn OFF lights. Then, being a good computer scientist I created a flow chart.

Flowchart: Garage Door Sensor associating with Light Switch
Flowchart: Garage Door Sensor associating with Light Switch
Now, I installed the Z-wave 2-way switch module by replacing the old switches. Then I used the association in Vera controller to make a relationship between the sensor and the light switch.

Here is an example video of an association (not the same one describe above).

You can resolve problems similar to this using associations in many other situations. Here are few example of typical problems that can be fixed using association method.

  • Turn on lights (switch module) when the motion senator (sensor module) is tripped if the time period is night.
  • Turn off the TV (plug-in module) if the motion sensor (sensor module) have not been tripped for over X hours in the entertainment room.
  • Turn on the sprinklers (plug-in module OR sprinkler controller module) if the light sensor (sensor module) detects low lights and it is at night.
  • If the light level (luminance sensor) is below 90 lux then turn on lights.
  • If the humidity level (humidity sensor) is below 40% turn on the humidifier and send an email.
  • If you install a multisensor, Boolean logic possibilities can be significantly increased.
  • …and many many more!

The key to a successful association type automation is proper planing and right equipment.

Improvised home automation

The ideal solutions for home automation devices are usually plug-and-play units or modules. They often require just powering the unit and adding to your main controller. I came across unique situation in which a Z-wave, x10 or Insteon modules does not exists, but a solution can be made by combining automation modules with types of electronic/electric units. It is technically an improvising what you can get on the market. However, it does not necessarily means the final outcome of these projects are lower in quality compared to plug-and-play solutions.

Electric shock alertPlease note that some modifications may result in voiding the manufactures’ warranty. Some project involves working with ~ 110/240 volts alternating current (AC). Even with the power cut offed, there is always a risk of electric shock.

Garage Door

Currently there are no manufactures or distributors in Canada that sells openers with automation as a built-in function. I have used a inline relay module between the traditional opener switch and power. If you are unfamiliar with what is an inline relay, check these items: Fortrezz MIMOLite Zwave Input Output Module and Evolve ZWave Inline Relay Module-LFM-20.

These relays acts as a human input to any device that has a ON/OFF type switch(es). Some of these may not work for devices that require continuous ON such as an electric heater. Make sure you read the manufacture’s datasheets before purchasing.

Door Opener

Yes, you can buy a automated door locks from companies like Kwikset, Schlage and Yale. But it will only allow you to either lock or unlock your door. What if you want to open the door remotely? To do that you need a motorized door opener. You can buy a door opener unit for either swing door or slide door type. They comes with an electric motor, mounting equipment, a switch and a remote. What lacks is any form of automation controlling unit (Z-wave, x10 or Insteon).

When you are purchasing a electric door opener, make sure it also has a push-button connection. You will replace this push-button with your inline module.

Again, we can use an inline module like MIMOLITE between the motorized door openers such as Skylink Otodor Automatic Swing Door Opener and its power supply. Then by adding the the module to network, you can open and close the doors with your computer or phone.

Security Cameras

There are several companies that produce high quality cheap security cameras. For indoor use, almost all of the reputed companies make great products that are simply plug-and-play modules. I also like the fact they are often independent standalone units. In other wards they can operate without a central controllers like Z-wave controllers.

In Canada, we run into one big problem; weather. Most wireless outdoor cameras are built to work between -20 to +40 degrees Celsius. In most parts of Canada (such as Calgary) we get temperatures as low as -40 oC during Winter months. You could buy a extreme weather cameras with a heated casing. But it will not only cost a lot for the unit, but also the subsequent costs for heating will add up over the years. Hence we must improvised with these cheap IP-Cameras if we want to use them outside.

Solution 1: Use indoor units

You can install a high grade indoor camera such as D-Link DCS-5222L close to a wide outside window (inside the house). Now by pointing the camera towards the outside, you can still surveils the outside without having a weather proof unit. The major drawdown is that the Infrared (IR) LEDs will bounce off the window at night causing distorted image. This can be overcome by turning off the IR mode and illuminating the outside area with a flood light.

Solution 2: Install on the other side

If you want to protect areas like your garage, you can install the camera inside instead of outside. In most situations this will provide adequate protection from weather. The darwdown is that if you have an enclosed area, you will not be able to see the outside. However, if someone breaks into the garage, that can be recorded.

Solution 3: Creating your own weather casing

This is really a improvised do-it-yourself project. You can create a metal or wooden box and add a HVAC pipe into the box from your house. So whenever the house is heated, the camera enclosure will also be heated. Please make sure that you are doing this according to the laws of your area. Some cities and countries would not allow you to use such methods due to safety reasons.

Last option is not really an improvise. You can just buy a Canadian outdoor weather reared camera. In December 2013, it will cost you around $300 to $2000 depend on the manufacture and the model.

When installing a wired outdoor camera (or anything else), make sure to use outdoor rated cables.

Plumbing

I would not buy a fully integrated taps or water controllers. This is because electric taps are often well-built. However, the electronics go into the automation can be unreliable. You do not want a leak after few years of use or unwanted turn on/offs. The solution is to buy an electric taps/water controllers with a push-button switch. Hence, the automation part will be added using a inline module that is independent of the water controller itself. Easy to install and easy to do maintenance work.

Electrical

I would not recommended improvising for anything to do with electrical. It not only pose a hazard to your health, but also could lead to criminal charges. But there are something you can do in your own home. Even the garage door and light switches automation involves electrical modifications.

Missing Common Wire

If you have a situation in which a Common Wire (“white wire) is not available in your house or the area in question, you have two options. One is to run a Common Wire from your main board to the location, and the second is to use a plug-in module. If you are not familiar with electrical work, I recommend the second option. You can connect lamps, electrical appliances, consumer electronics and many more to a plug-in module. Make sure you use the right module with proper rating. The module will plug-into the wall outlet and provide outlet with automation. The Evolve ZWave Plug-In modules are examples of such units.

LED dimmer causes flickering

This is a very common problem with LED dimmers and not the Z-wave module itself. Sometimes when the resistance, R on the circuit is extremely low and the current, I flow is also reduced through the dimmer, it will cause the LED lights to flicker. This happens when the dimmer at its lower illumination setting.

To resolve this we need to increase the resistance in the circuit. The best solution is to install at least five to eight LED light bulbs in a single circuit. You can try by adding one at a time until you no longer have this problem. If that is not viable solution, install a mixture of both LED and regular bulbs on the same circuit. However, I found by mixing manufactures of LED bulbs I was able to stop the flickering with just three LEDs.

Outdoor electrical modules

When working on an outdoor automation project, use outdoor approved electrical products. For example, GE ZWave Outdoor On/Off Module-45604 should be used when you are installing a sprinkler system. Do not try to save money by buying an indoor module to control an outdoor electrical products. There is a reason why outdoor units can be bit more expensive!

Please be aware that you may not be able to automate anything and everything. Use common sense and if you are not sure of something, do your research and/or ask an expert. Most manufactures and distributors also provide free support. Use them as a resource.

Advantages of Improvising

There are several advantages. I decided to list them so you can quickly glance through each one.

  • In-line modules can be from any manufactures and can be on any standard (Z-wave, x10, etc)
  • Most of the time, it is easy to install with improvised solutions (describe in the article)
  • If a unit/module fail, it is easy to replace as opposed to replacing an expensive and complicated unit
  • Parts can be easier to find (for example, an electric tap from Canadian Tire and a controller module from a Z-wave specialty store)
  • May be more reliable than having a single plug-and-play
  • Can be install on almost any house regardless of the age of the house or the electrical wiring/plumbing/door system
  • Provide much more expansion possibilities