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b. Current sensing
c. Battery control
These functionalities are not built into the Watchdog board however it does have the
necessary ports enable them to be carried out.
4.4.3.1 Radio transmitter and amplifier
The radio transmitter is needed to send an SOS signal in the case of emergencies. This
signal will be emitted by the FM-RTFQ1 module which is sold by RD Solutions
Company. This is a fully designed and embedded radio emitter that does not require
external components and works in the 868MHz frequency range. We can see the radio
transmitter in the Fig. 55 with the identification IC3.
Fig. 55 Radio transmitter with the corresponding radio amplifier
The radio amplifier is required in order to increase the signal from the radio
transmitter. In this module, there are many more components than in the previous
ones. The radio amplifier consists of the following components: IC4, C6, R6, C7, ANT1,
L1, C8 and C9. The main core of this module is the IC4. This is a wideband medium
power amplifier that will increase the power signal from the radio transmitter. This
Silicon Monolithic Microwave Integrated Circuit (MMIC) is sold by the Semiconductor
division of PHILIPS.
In Fig.55 we can see the components position and its corresponding values. This
position and value is recommended by the specification sheet given by PHILIPS
Semiconductor with this device. In the Watchdog PCB, the corresponding ports that
link the radio transmitter and radio amplifier will be the PA5 and PA6. The PA5 is the
power port that will give +5V and +6V to power up the amplifier and the transmitter.
PA5 port is the radio control port, this is one of the pins is that will turn on or off the
radio device and the other one is used to send the rescue signal to be emitted.
4.4.3.2 Current sensing
The current sensing port, Fig. 56 , has the task of receiving the proportional voltage in
accordance with the current that in real time is being consumed by the main battery.
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