A NOVEL SECURITY SYSTEM
USING A RENEWABLE ENERGY SOURCE
The events of 2001 changed the way we in America act with regard to safeguarding our assets. No longer do we leave our keys in the car, leave our doors unlocked, and allow strangers to roam our residential streets unchallenged.We have altered our level of complacency because we now know there is evil in the world,and it is seeking to destroy us. Surveillance and security are now necessary factors in the design and plan of almost everything we do or create. The need to provide protection against intrusion for our homes, workplaces, schools, and other areas of our lives is a consideration in everything we do. To respond to this need, we have developed this concept for a security device that provides such protection at minimal cost.
The security system is a prototypical, self-powering device that will potentially generate a significant alarm or signal when any integrated parameter is breached. This signal can beused as a first alert mechanism or incorporated into a wide area surveillance network.
We have harnessed an electrical property of ceramic materials called piezo electricity. This is anenergy scavenging or energy conversion capability that is becoming increasingly popular as a means of creating self powering electrical devices. Making thiscapability even more attractive is widespread use of piezoelectric ceramic elements in other commercial products has created an abundant supply of new materials with characteristics that are of significant interest to our applications. From our perspective, it is imperative to explore these materials as well as other components we have envisioned for our system.
1. How It Works
First demonstrated by Pierre Curie in 1880, the directpiezoelectric effect is the generation of an electrical voltage by applying pressure to specific crystalline materials such as quartz. This voltage is aresult of distorting the crystal structure and the subsequent changing in theelectrical charge distribution surrounding the atoms. In practice the direct piezoelectric effect can easily be used to convert mechanical energy to electrical energy.
One popular application of the direct piezoelectric effectis the creation of a spark for gas ignition in stoves and furnaces (Figure 1).When a button is pressed, a spring loaded actuator impacts a cylinder made ofPZT (lead zirconate titanate, an extremely high conversion efficiency ceramicpiezoelectric material). This action generates an instantaneous potential ofnearly 7,500 volts, sufficient to cause an electrical discharge across an airgap, much like that seen at the tip of a spark plug.
Figure 1:Piezoelectric Gas Igniter
The PZT element within the igniter has dimensions typic allyon the order of 7-10 mm in diameter and 12-15 mm in length, making it verycompact and easy to conceal.It also can be cycled 200-300,000 times without degradation and is chemically very stable making ita long lasting and trouble free device. In bulk quantities it is quite inexpensive, ranging from$0.10 to $0.25 per element.
PZT elements can be incorporated into mechanical structures that produce voltages suitable for other applications, such as powering transmitters or alarms.Aself-powered alarm would beidealfor security monitoring systems, with the primary advantage being no externalpower source or batteries are required.This means sensorinstallation would be simplified, routine maintenance would be reduced, andthere would be greater opportunity to locate sensors wherever desired.
Given these advantages, we propose incorporating piezoelectric actuators into a door or gate hinge. The purpose is to scavenge the mechanical energy of the swinging door and create a power generator that produces a useable voltage upon actuation (Figure 2). In our application, the voltage would be used to drive an alarm mechanism such as a light, a buzzer, or,ultimately, a radio frequency transmitter that can broadcast over a wirelessl arge area network or Wi-Fi.
The action is surprisingly simple:
1) A power generating cell comprised of asingle or multiple PZT (or equivalent) elements is positioned within, or in thevicinity of, a door hinge.
2) The door or hinge contains an actuatormechanism that contacts or releases from the power cell when the door is openedor closed.
3) This PZT cell is in turn connected to analarm element whose operating characteristics are matched to the cell’selectrical output.
4) When the door is moved, a voltage pulseis created, driving the alarm element and signaling intrusion. Alarms can bevisible, audible, date stamped, or wireless communications to a receiver in theproximity.
5) The alarm can be reset after intrusion bysecurity personnel, if needed.
Figure 2:Self-Powered Piezoelectric Door Hinge Alarm
Initial experiments indicate that sufficient current can be generated at a low voltage. This can provide enough power to light an LED or trigger a simple buzzer and is the first step in developing a battery free,external power free, and maintenance free sensing system. With additional effort, we could create ultra low-cost security devices that can be easily retrofitted to doors, windows, gates, ingress and egress areas, or just aboutanywhere. Above all, these devices may be used to monitor any security breaches.
We have also begun researchinto low-power RFID devices that could be integrated with the hinge to a Wi-Fidevice that does not require batteries or hard wiring. This additional researchcould eventually integrate into a full network.
Mr. Scott Grimshaw, Principal Investigator
Mr. Grimshaw has an extensive background in solid state electronic materials, piezoelectric sensors, semiconductors, and device manufacturing. Heh as been awarded eight patents on a variety of scientific applications.
He is the founder and current president of Tangidyne Corp, amanufacturer and designer of piezoelectric thin film sensors. Mr. Grimshaw wasalso founder and president of Cold Springs R&D, a quartz crystal sensorcompany.Past employment includesassignments with Xerox, General Electric, Standard Oil of Ohio, and LeyboldInficon.
Additional information may be found at www.scottgrimshaw.net or www.tangidyne.com.
Mr. Robert Salisbury, Principal Director
Mr. Salisbury has an extensive background with special security projects for the Air Force at SAC headquarters, Rome Laboratories, and the Defense Intelligence Agency. He has developed special intelligence data handling databases and performed risk assessment, penetration analysis, and disaster recovery planning for several government contracting companie sincluding IBM, Univac, Analytics, PRC, and others. Mr. Salisbury is familiar with and has worked with the rainbow series of guidelines sponsored by NSA.He is a member of ASIS.
United States Patent Number 7,122,944
United States Patent Number 7,218,215
Definitions of these patents and others may be found at www.scottgrimshaw.net.