rahulpsharma
Junior Member level 2
Dear Experts:
I am trying to copy and make a LVDT excitation Circuit from the following link:
https://www.mikesflightdeck.com/lvdts/lvdts.html
I need help in understanding and troubleshooting the last circuit schematic (Signal Source) in the above link...!!
The stated aim of the circuit is to generate 1kHz frequency at 2VAC at the emitter of 2N3906...
When I first soldered all components and turned ON the power supply, I got exactly 1.078kHz @ 1.95VAC at Pin 8 in the schematic.. However, at Pin 6 the freq remained 1.078 kHz but voltage dropped to 0.6VAC... And at the emitter of 2N3906, both freq and voltages were '0'...
Today, when I tried working on the circuit again, NOTHING is working... The results I observed yday are also gone... Freq and voltages at every pin described above is 0...!!! :-(
So now, I wish to gain some understanding of the ckt and logically proceed to troubleshoot it...
I've made a PCB of this ckt and soldered components so I am ruling out the possibility of any loose connections... Moreover, I've replaced the main IC TL084 but there has been no change...!!! Please help me understand this circuit:
I have the following questions now:
1) Which components of this ckt determines the frequency and AC Voltage Levels...
2) From the ckt, there appears to be no external signal applied to the Op AMP, then how does it generate freq and voltage at Pin 8...
3) What is the purpose of the final part of this ckt comprising of two transistors, three diodes and one section of TL084 (Pins 5,6 & 7)...
4) What will be the shape of the waveform when the ckt works: sine wave?
Some deviations that I have taken from the original circuit are as follows:
a) I didnt have a 7808 IC readily available so I have used 7809, instead...
b) Instead of Polar capacitors, I have used Ceramic ones
c) I could not find a 20 pF exact value so I am using 22pF
Thanks and regards
Rahul P Sharma
I am trying to copy and make a LVDT excitation Circuit from the following link:
https://www.mikesflightdeck.com/lvdts/lvdts.html
I need help in understanding and troubleshooting the last circuit schematic (Signal Source) in the above link...!!
The stated aim of the circuit is to generate 1kHz frequency at 2VAC at the emitter of 2N3906...
When I first soldered all components and turned ON the power supply, I got exactly 1.078kHz @ 1.95VAC at Pin 8 in the schematic.. However, at Pin 6 the freq remained 1.078 kHz but voltage dropped to 0.6VAC... And at the emitter of 2N3906, both freq and voltages were '0'...
Today, when I tried working on the circuit again, NOTHING is working... The results I observed yday are also gone... Freq and voltages at every pin described above is 0...!!! :-(
So now, I wish to gain some understanding of the ckt and logically proceed to troubleshoot it...
I've made a PCB of this ckt and soldered components so I am ruling out the possibility of any loose connections... Moreover, I've replaced the main IC TL084 but there has been no change...!!! Please help me understand this circuit:
I have the following questions now:
1) Which components of this ckt determines the frequency and AC Voltage Levels...
2) From the ckt, there appears to be no external signal applied to the Op AMP, then how does it generate freq and voltage at Pin 8...
3) What is the purpose of the final part of this ckt comprising of two transistors, three diodes and one section of TL084 (Pins 5,6 & 7)...
4) What will be the shape of the waveform when the ckt works: sine wave?
Some deviations that I have taken from the original circuit are as follows:
a) I didnt have a 7808 IC readily available so I have used 7809, instead...
b) Instead of Polar capacitors, I have used Ceramic ones
c) I could not find a 20 pF exact value so I am using 22pF
Thanks and regards
Rahul P Sharma