Environmental Engineering Reference
In-Depth Information
500 us/div
(500 us/div)
NORM:2 MS/s
CH1 = 1000 V
DC 1000:1
T
1
= Trace 1 = Max
5.440 kV
20 us/div
CH1 = 1000 V
Zoomed
1
FIGURE 4.5
A piezoelectric push-button igniter.
piezoelectric element. Hence, it is critical to ensure that the harvested energy
is sufficient to transmit a few packets of information through the RF trans-
mitter in a wireless manner.
Figure 4.6
shows the 12-bit data encoded by a
HT-12E encoder to be sent out by the RF wireless transmitter.
The encoder first generates a synchronization starting bit following an 8-bit
address [1000 0000] and 4-bit data [0101] sequence serially. The address
data
pins of the HT-12E encoder have been prefixed to the [1000 0000 0101] se-
quence to be sent to the transmitter. The key for low energy consumption lies
in the fact that in many applications, transmitters are idle most of the time.
Therefore, the proposed concept of piezoelectric push-button power gener-
ation fits snugly since transmission will only be required when the push
button is being depressed, like the case of typical wireless remote controllers.
In order to power the RF transmission operation, which takes approximately
tens of milliseconds for a complete 12-bit information transmission as shown
in
Figure 4.6
, the electrical energy has to be stored properly in order to en-
sure complete transmission operation even when the external power source
is temporarily unavailable. During this time, the transmission operation is
constantly consuming energy until the process is completed where only a
minimal amount of energy is needed by the transmitter circuit during the
standby mode.
/
Search WWH ::
Custom Search