V21B Mide Technology Corporation, V21B Datasheet - Page 15

• Manufacturer Part Number: V21B
• Description: PIEZOELECTRIC ENERGY HARVESTER
• Manufacturer: Mide Technology Corporation
• Series: Volture™r

Specifications of V21B

• Sensor Type: Acceleration
• Sensing Range: 80Hz ~ 205Hz
• Output Type: Analog
• Operating Temperature: -40°C ~ 90°C
• Features: Piezoelectric Vibration Energy Harvesting, Hermetically Sealed
• Package / Case: Cantilever Piezo Film (Wafer)
• Mounting Type: Through Hole
• Termination: PC Pins
• Lead Free Status / RoHS Status: Lead free by exemption / RoHS compliant by exemption

APPLICATIONS INFORMATION -
Goals
Simple “One-Shot” Application
A simple usage scenario is an embedded sensor with
data storage/transmission capability, which takes one
set of measurements each time it is powered up
(relying on the loss and subsequent re-application of
power to start the next measurement). In this case, the
measurement frequency is variable and depends on the
vibration amplitude. To operate the sensor directly from
the boost circuit requires:
For such one-shot sensors, it is recommended to
create a large load (e.g. drive an LED or GPIO pin tied
to ground) after completing the task in order to ensure
the power output cycles in high-vibration conditions.
A typical microcontroller sensor application’s load
profile will be “bursty”, complicating the task of
estimating the required value of CP
load can be approximated in terms of a resistive load,
the following equations can be used to estimate the
required capacitance, available runtime, energy per
discharge or power stored.
Allow intermittently operating circuits to be
powered from extremely weak vibration sources,
or moderate vibration sources at frequencies sig-
nificantly different from the energy harvester's res-
onant frequency (Figure 3)
Physically disconnect the load during periods of
insufficient voltage to avoid "over-the-hump" prob-
lems of cold circuit start-up from harvested power
Maximize chances of success where vibration
source's characteristics (amplitude and frequency
content) cannot be known in advance.
Estimation (or measurement of) the run-time and
power consumption of your application within its
voltage limits
Sizing the CP
allowing some headroom
out
according to worst-case usage,
out
. However, if the
REVISION N0. 001
SWITCHED CAPACITOR BOOST CIRCUIT
REVISION DATE: 06-03-2010
In the equations above, T
time in seconds, T
the equivalent load resistance in ohms, V
starting output voltage (2.4), V is the final output
voltage (1.8V or the minimum operating voltage of the
sensor, whichever is greater), and C is the capacitance
in Farads. Likewise, the output voltage can be modeled
as a simple RC time constant, V = V
Continuously-Powered Application with
Input-Dependent Triggering
Sometimes it may be advantageous to incorporate
vibration-powered
triggering into a continuously-running circuit. For
example, a sensor may require low-level continuous
power to maintain a realtime clock, but measurement
tasks are only needed when a piece of machinery is
known to be operating. Alternately, it may be desired to
dynamically adjust the measurement rate based on the
incoming power to maintain a given power budget. In
Equation 1: Capacitance needed for
Equation 4: Average Power (Watts)
Equation 3: Energy per discharge
Equation 2: Runtime for a given
(Joules or watt-seconds)
W
c
T
C
a given runtime (F)
capacitance (sec.)
d
is the charge time in seconds, R is
P
battery
1
2
T
1
R C ln
C V
d
T
d
c
R ln
is the runtime or discharge
W
1
0
2
T
d
maintenance
V
V
V
V
V
o
o
2
0
e
-T/RC
.
0
and/or
is the
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