Vibration Energy Harvesting System - Energy Harvesting Autonomous Sensor Systems - page 135

by the equation: ( R 1 + 2 R 2) = 1 . 44 / ( f ∗ C 1). The components chosen are

R 1=1K , R 2=80K ,C1=1.0 F, C2 = 10 nF. Oscillator resistance (Rosc)

is fixed at 82 K because the RF transmitter is operating at 433 MHz. The

output of the JK flip-flop can be connected to a relay to turn the connected
electrical appliances on/off.
Referring to Figure 4.25 , it can be seen that an AND gate is added to D8
of the decoder. This means that if the transmitter sends a “high” on the cor-
responding data bit, it toggles this circuit. Thus, this circuit is considered to
be “tagged” with the first data bit and by the same logic, four more receivers
each tagged to the other four respective data bits can be built. By doing so, a
single transmitter will be able to control up to four different electronic devices.
In addition, this design saves the cost of having to buy one switch for every
appliance, especially when it comes to appliances that are usually grouped
together, such as a set of four lights in a single room. This will also eliminate
the hassle of having to find the individual switch for a particular appliance,
as well as having to allocate space for four switches.

4.2.5 Summary

In this impact-based energy harvesting research, a batteryless wireless con-
trol switch using a prestressed piezoelectric diaphragm material has been
proposed for applications in warehouses, commercial buildings, and so on,
to cut high wiring costs, including material, and labour expenses in laying
power and signal cables from control switches all the way to the electrical
appliances can be reduced tremendously. In addition, no maintenance cost
and effort are required for the wireless control switches. The self-powered
wireless control switch is also highly suitable for those appliances located in
remote locations that are too difficult or hazardous to access and also suitable
for applications where multiple electrical appliances have to be controlled si-
multaneously. Unlike the piezoelectric igniter system, the prestressed piezo-
electric diaphragm material is more applicable for low-force environment,
and its output voltage is relatively low. Since the electrical power throughput
of the piezoelectric material is less than the power requirement, an energy
storage and supply circuit has been implemented. By doing so, 0.83 mJ of
energy is first stored in the capacitor until the preset voltage level of 12 V, and
the stored energy is supplied to the RF transmitter load through a voltage
regulator of 64% efficiency. From the experimental test results obtained, the
harvested energy output from the voltage regulator of 0.53 mJ is sufficient to
power one successful wireless transmission for a distance of 20 m.