Column: Circuit drill
Annunciator circuit performance at decaying power supply voltages
By Dr. Sulaiman Algharbi Alsayed, Managing Director, Smart PCB Solutions
crucial for safety purposes, as they alert operators to avoid accidents or improper procedures. Annunciator circuits are found in security, fire, machine malfunction and medical alarm systems. The circuit shown in Figure 1
A
represents a typical annunciator circuit, widely used due to its simplicity and ease of construction. It is designed to activate an audible alarm through a speaker or buzzer, shown as R5 in the figure. Figure 2 shows the
nnunciator circuits produce audible signals when faults or unusual activities occur in a system or a process. They are
waveform generated by the circuit. It is important to ensure the reliability
and functionality of these circuits under all possible circumstances, including when power supply voltage begins to decay. This experiment should show us the
limitations of the annunciator circuit when the power supply voltage drops below the standard 5V.
The experiment We used the circuit shown in Figure 1 for the experiment, and applied a range of voltages to it, with the peak-to-peak output current passing through the speaker, R5. All the monitored current peak-to-peak values were plotted against each applied voltage, which was varied
from 0Vdc to 15Vdc in 1Vdc steps; see Figure 3. All electronic components were kept fixed throughout this experiment. Figure 3 shows that the circuit is very
stable at the higher end of the power supply range, specifically between 5Vdc and 15Vdc. However, when the voltage decreases, the situation changes: Below 7Vdc, the circuit's output starts to decline significantly. At 4Vdc, the circuit stops functioning, with no output observed. This finding is important when
building circuits, to ensure the power supply is higher than 5Vdc, otherwise this circuit won’t be reliable and its proper functioning will be compromised.
Figure 1: A popular annunciator circuit
10 February 2024
www.electronicsworld.co.uk
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44
