WiFi Linux Wall Wart

Linux based wall mounted system for environmental research and interaction.

As most of our Gizmos, this one was suggested by one of our members. The idea was to have these Wall plugs through out the house and by means of gestures and sound commands to be able to control different appliances, security and other house-hold hardware. In this description we shall explain all main parts of the device and the reason for their existence.

Specifications

- Self contained internal power supply for using the wall plug, operational at 120v - 230v AC
- 2 x 3MP Cameras - OV3640 (Gumstix 27pin Flex Ribbon included)
- Digital Compass for orientation - HMC6352
- USB Port for Programming & Debugging
- Internal Speaker for Audio
- 2 x High End Microphone PreAmps for high Audio Sensitivity (2 internal microphones included)
- Bluetooth & WiFi antennas included
- 4 Diffused RGB LED's for various operation notifications
- Audio In 5mm Stereo Jack
- Audio Out 5mm Stereo Jack
- The device operates with the Gumstix Overo series of platforms (Overo Air Recommended)
- Dimensions: (L) 104.369mm x (W) 56.718mm x (H) 38.481mm

External Parts

Externally the device looks like the image below. We begun manufacturing the latest version of this Gizmo with a White enclosure as requested by the initiator of this idea.

As you can see all of the Antennas, microSD card slot, RGB LED's and other described above features are clearly visible. Additionally we included a small Red LED to indicate main power status of the device. The two cameras are located approximately at the center of the enclosure and are widely spread apart for Stereoscopic vision or other purposes. 

The Plug it self is a US Type wall plug with a Ground Pin. Adapters for other wall plugs can be easily found for other country specifications. The internal Transformer can convert 120v as well as 230v AC so there is no need for any additional hardware required to be able to start working with this Gizmo.

Internal Parts

Internally the device is assembled from 3 different PCB's which are connected to each other, making the device unique in it's operation. Below we shall describe each one of these parts and what is it's functionality.

Power Supply

The device is powered by 5v - 1000mAh DC power source which converts the 120v - 230v AC Wall Plug voltage to the above described value. It is a Switching power supply so there is no need to worry about it heating up and causing any damage to the device.

Main Motherboard

Above you can see the motherboard of the Gizmo. This board hosts all of the voltage regulators needed for different parts of the device. Also you will find present the 2 x 70pin headers for the Gumstix Overo board which is the main Processing unit of the entire device.

All of the Connectors for the Microphones, Speaker and Camera PCB are located on the Top side of the board for simple assembly and dis-assembly  since if you choose to purchase the Gizmo without the Gumstix Overo platform this feature will become very handy.

Clearly you can also see the 2 Stereo 5mm plugs for Audio In and Out. We included these plugs in case someone would want to use headphones or external microphones on this Gizmo and experiment with different configurations.

Camera Board

The Camera board hosts the 2 x 3MP cameras with all of the required voltage regulators as well as the 4 x RGB LED's for status indication. This board connects to the Motherboard through a 35pin FLEX ribbon and carries all of the camera, power and LED signals.

One thing to have in mind about the RGB LED's is that they are connected to the LCD data bus. Meaning that in order to be able to use them you will need to initiate the pins as GPIO's. Optionally you can just leave them as is and when there is LCD activity you shall see some pretty cool effects generated by the LED's.

Microphone Pre-Amps

One of the main features on this Gizmo are the two microphone Pre-Amps. For the Initial idea to work we needed to make the microphones as sensitive as possible so that a person who is 2 - 5 meters away from the device could still be heard and recorded through the on-board processor. 

Below are the specifications for the Pre-Amp (PGA2500):

- Fully differential Input-to-Output Architecture
- Digitally controlled Gain using Serial port interface

-- Gain Range: 10dB through 65dB, 1dB per step
-- Unity (0dB) gain setting via serial port or Dedicated control pin.

- Dynamic performance:

-- Equivalent Input Noise with Zs = 150 ohm and Gain = 30dB: -128dBu
-- Total Harmonic Distortion plus Noise (THD+N) with Gain = 30dB: 0.0004%

- Zero Crossing Detection minimizes audible artifacts when Gain switching
- Integrated DC Servo Minimizes Output Offset Voltage
- Common-Mode Servo Improves CMRR