Complete fiber optic systems are finding wide spread use in all types of applications figure 1 provide a very simple fiber optic telemetry system that can be used in a variety of telemetry application essentially the transmitter is an astable oscillator using the popular NE555 (IC1). The variable resistance LDR1 contract the rate of pulse applied to the LED. LDR1 can be any variable resistance transducer such as a strain gauge for pressure sensing, a thermister for temperature sensing, or a photoresistor for light sensing. It could also be a carbon microphone so as to transmit audio information. The transmitter is essentially a voltage/frequency (V/F) converter, and thus any of the IC V/F chips (such as the LM331) could be used in this application.
The receiver circuit shown in figure 1 used as MC 1458 (IC2) dual op-amp as a preamplifier (first op-amp) and as a comparator (second op-amp). Once the receiver paulses and cleaned up by the comparator, they are applied to the IC3 (NE555) used as a frequency-to-voltage converter. Adjustment of VR1 controls the threshold level of the comparator, while VR2 permits calibration of the output meter. The simplicity of this system makes it easily adapted to a variety of application.
PARTS LIST OF FIBER OPTIC TELEMETRY SYSTEM
|Resistor (all ¼-watt, ± 5% Carbon)|
|R1 = 1 KΩR2, R3 = 100 KΩR4 = 1 MΩ|
R5, R6, R8 = 5 KΩ
R7 = 10 KΩ
VR1, VR2 = 10 KΩ
|C1, C5 = 0.22 µFC2 – C4,C6 = 0.1 µF|
|IC1, IC3 = NE555IC2 = MC1458LED1,|
|LDR1M1 = 0-1mA ammeter Optic Cable|