Devices Studio

Ever had a doh! moment?, that is the moment when the door slams behind and you slap your forehead realising you left the house without taking the keys.This device is the response to that “thoughtless act”, that daily ritual everybody performs to remember not to forget. The target audience is everyone of us but specially aims to assist those with short term memory issues.Through my previous research, I identified that most of the techniques employed by people to remember the important items they need to take with them, consisted basically in grouping items together and placing them in a meaningful place. With this in mind I decided to design a system that would create virtual groups of items and link them to the place associated with the action of leaving the house: the door knob.

 

Tags, the concept as a product

The system is designed to be modular and expandable. The only fixed parts are the reader/antenna and the knob device.

Since the items have to be tagged there’s an opportunity for both overcome the unsexy operation of sticking an RFID tag into your daily use objects and a business potential, creating wrapping objects containing the tags to be acquired separately from the starter kit.The wrapping has also the mission to associate a color with each object, in this way the system “suggests” and not explicitly tells the user which kind of item she might be forgetting. This information is displayed in the knob device, by means of color lights, an additional tangible feedback is provided by vibration.Currently the wrapping objects are designed for the most common items:

• Keys -> The good old keyring.
• Phone -> A silicone phone case.
• Waller/Purse -> A credit card/id size plastic card.
• Documents -> A plastic bookmark with a clip to attach to paper objects, such as reports, books, diaries, passports…

There’s a special kind of wrapping object, this is a detachable oval-shaped box that can be attached to very important items that are not of daily use. This special tag will beep when missing, revealing its location.

 

Interaction

Ergonomics
The main interaction with the device is by touching the knob. The principal idea behind the concept is enhancing the act of opening the door, hence the design of the knob device is critical to ensure seamless interaction and minimum corruption of the original action.

Prior to decide on the shape of the device, 3 prototypes were built in foam, the last one -chosen for being the best balance in between aesthetics and ergonomics- went through a process of refining to optimize the room available for the circuitry and minimize the impact in user’s hand posture when turning the knob.

 

 

 

 

 

The scanning hardware requires a pretty big antenna, approximately 25x25cm, this big device has to be wall powered and sit close to the door to be able to scan the user as she goes. The antenna itself has been modified to accomodate most of the electronics and relieve the other devices, the peg allows to regulate the orientation of the antenna or to hang it from the wall.

 

Color codes and tangible feedback

Each kind of item has a color code associated:

• Keys – Yellow
• Documents – Red
• Phone – Magenta
• Wallet/Purse – Green
• Special detachable – Blue

When one object is missing the knob will blink twice its color in an interval of one second, to ensure the user doesn’t miss the first feedback.
When more than one object is missing, the knob will cycle the colors of all the missing objects in a one second interval.
The vibrating motor will provide tangible feedback simultaneously with the light’s blink.

In the same way there are two color codes for special events.

• Plain White, the knob device lites in white once it no object is missing, this positive feedback is necessary to inform the user of the proper operation of the system, the soft white light is both non-disturbing and visual appealing. No vibration in this case.
• Fast Red – “Alarm” – the user is leaving the house without carrying any object. The light will blink three times in red in intervals of half a second. So will do the vibration.

Grouping Items
People don’t take always the same items with them, on the same way, more than one person can be living in the same household. The solution to address both multi-situation and multi-user is by “grouping” the items.

By pressing the button on top of the host device once, the status lamp will switch from green to blue for ten seconds, during this period of time all the unknown tags in front of the host device will be included in the system’s inventory.

Items are added to groups using a “reference item”, i.e. if user wants to include her purse in the keys’ group, she will have to “show” both keys and purse at the same time to the system.

When no “reference item” is used the system will create a new group for the item.
When an item is registered into the system, the status light will blink briefly in the color code matching the registered item. At the same time a beep will be heard indicating a successful operation.

After ten seconds a beeping tone will indicate that the system is exiting the registering mode and the light will go back to green.

Removing items
By keeping pressed the host system’s button for longer than three seconds the system will enter in removing mode. The status light will turn red for three seconds and during that period of time all the items in the system’s range will be deleted from the inventory.

When an item is removed from the system, the status light will blink briefly in the color code matching the registered item. At the same time a beep will be heard indicating a successful operation.

The Nitty-gritty

The system consists on two main parts: scanning and tagging.

The scanning device
The scanning device is fixed and must be placed in the proximity of the door, it has two parts:

The host device
In passive mode the system is continuously scanning for known items on its proximity, creating a list of missing items and storing it for a period of 30 seconds, this time is estimated to start scanning the user while she is walking to the door. Adding a proximity sensor will avoid this.

When the host device is enabled will send the list of forgotten items to the knob device for displaying. The list will have only one element with the special codes “0” for “all is good” and “-1” for “Alarm”

The knob device
Acts as a switch and as a display, it consists of a standalone XBee radio chip that communicates with the microcontroller in the host device.
On the upper inner part of the device’s loop there’s a metal pad that makes contact with the metal at the door’s knob. This metal strap is connected to a NPN transistor’s base by a resistor and the transistor’s collector to power with another resistor, this is the simplest kind of touch switch known, when the user touches the knob and increase in the resistance will open the base and let the power flow through the transistor, sending an “enable” signal to the host device.

The RGB LED on the top part of the device will display the color code corresponding to the data received from the host device, the vibrating motor will vibrate accordingly to the light’s blink.

The buzzing tag
This special tag has a standalone XBee radio chip that will receive a signal from the hot device when it’s declared forgotten. This signal will make a buzzer piezo beep constantly until the tag is found and its stop button is pushed.

Doh in action

Enough of talking

 

Circuit diagrams

Host

Knob

Buzzer

Component List

• 2 Arduino Duemilanove (My UNO died and I had to connect two in I2C due to the lack of serial ports)
• 1 Lilypad (not really necessary, it’s only used to generate a square wave for the piezo buzzer to beep)
• 3 XBee radios, 2 standalone, 1 in shield
• 2 RGB LEDs
• 2 piezo speakers
• 1 vibrating motor
• 2 voltage regulators 3.3V
• 2 NPN bipolar transistors
• 1 UHF RFID reader, ISO 8000 6c EPC Gen2, reading range ~6m, (AUD170)
• 1 UHF antenna (AUD120)
• 5 UHF RFID tags,  EPC Gen2 (900 Mhz)
• Knob device laser printed in perspex
• Detachable tag 3D printed with MakerBot