LITERATURE REVIEW
In order for me to get a broad knowledge on the project; I researched into similar sensor project that has being performed or has been finished. I explored into projects that were being designed or has been developed from several engineering associations, like Cypress (Chethan.ASarki, 2013), Computing, Information Systems, Development Informatics & Allied Research Journaland other government projects.
Proximity Sensing with CapSense was constructed by Chethan(Chethan.ASarki, 2013), using proximity-sensing technique based on CapSense involves measuring the change in the capacitance of a proximity sensor when a target object approaches the sensor. The target object can be a human finger, hand, or any conductive object. Proximity sensors based on CapSense can be constructed using a conductive (usually copper or indium tin oxide) pad or trace laid on a nonconductive material like PCB or glass. The intrinsic capacitance of the PCB trace or other connections to a capacitive sensor results in a sensor parasitic capacitance (CP).
Figure.1 Proximity Sensing
When a proximity sensor based on CapSense is excited by a voltage source, an electric field is created around the sensor. A small number of electric field lines couple to the nearby ground, while most of the electric field lines are projected into the nearby space.
Figure.2 Electric Field Lines Coupling to Finger
Proximity sensing application based on Capsense
Various applications developed based on CapSense include the following:
Face detection in mobile phones and tablets
Specific absorption rate (SAR) regulation in tablets and mobile phones
Gesture detection in a human-machine interface (HMI) (Chethan A.Sarki, 2013).
Face detection in mobile phones and tablets: Face detection is a feature in mobile phones that disables the phone’s touchscreen and dims the brightness of the display when a user answers a phone call, as Figure 3 shows. Face detection prevents false touches when the phone is placed on the ear and optimizes the device’s power consumption. Using proximity sensing based on CapSense in this application offers advantages over IR proximity sensing because it does not require cutouts in the overlay material, which reduces the
tooling cost and improves the aesthetics of the end product.
Figure.3 Face Detection in Mobile Phones (Chethan.ASarki, 2013)
SAR regulation in tablets and mobile phones: SAR is a measure of the rate at which energy is absorbed by the human body when exposed to an RF electromagnetic field. Regulatory bodies like the Federal Communications Commission (FCC) require devices to limit the absorption of RF energy by reducing the RF transmit power of the device when the device is in close proximity to the human body, as Figure 2 shows. Proximity sensors based on CapSense can be used to detect the proximity of the human body and reduce RF power.
Figure 4. SAR Regulation in Tablets (Chethan.ASarki, 2013)
Gesture detection: Gesture detection is the technique of interpreting human body movements and providing gesture-type information to the device. Gesture-based user interfaces provide an intuitive way for the user to interact with the system, improving the user experience. Gesture detection is used in applications such as laptops, tablets, and mobile phones for controlling the user interface.
Proximity sensors based on CapSense can be used in these applications to detect gestures without any physical contact between the user and the device. Figure 5 shows an example of an implementation of gesture detection in a laptop where proximity sensors placed near the trackpad are used for the pan movement of the onscreen map.
Figure.5 Gesture Detection Implementation in Laptops
Oladunmoye M. &Oluwatomi A.A.(2014), used similar approached in constructing sensor sliding doors using IC-55 timer soldered on Vero board along with other integrated circuits to design an automated sliding doors.
A study performed in 2007 found that real-time safety technologies implemented onconstruction jobsites are capable of providing alerts to construction workers and equipment operators in real-time when a hazardous proximity issue is present (Teizer et al. 2010). These technologies can create a safety barrier and provide workers with a 5 “second chance” if another safety best practice is disregarded (Teizer et al. 2008). Some of these technologies are also capable of recording safety data that currently not obtainable, such as “close calls” or “near misses.” This new information and warning system can present new data sources and potentially improve safety in construction.
In 2001, Ruff found several proximity warning systems including RADAR (Radio Detection and Ranging), sonar, Global Positioning System (GPS), radio transceiver tags, cameras, and combinations of the mentioned technologies. The study found each of the candidate technologies to have limitations such as availability of signal, size, weight, and feasibility in the construction environment (Ruff 2001).
A few similar studies also investigated candidate technologies to combat hazardous proximity issues on construction jobsites. Technologies excluded from the study were those still in the prototype stage and not yet commercially available (Teizer et al. 2007).