bananasiong
New Member
hi all, sorry for creating a new thread because nobody reply there: https://www.electro-tech-online.com/threads/which-relay-to-be-used-dc-or-ac.21096/
i'm going to do presentation with this circuit 2 weeks later. if anything goes wrong, correct me ok?
The 555 timer produces a 10kHz(approximately) squarewave output at pin 3 with the combination of R1, R2 and C1. The 'antenna' will produce electromagnetic field on and off in 10kHz.
the resonant frequency of the tank circuit is 10kHz. the 100K resistor creates a gain of a few hundred thousand which is so high that it probably amplifies its own noise and any noise that is around. It might even oscillate.
If a 0.1uF capacitor is added to ground at pin 3 then it won't oscillate. When the signal is received then the output of the receiver should alternate between 0V and Vcc at the frequency of the input. With a 5V supply then the output's min current of only 6mA should be able to saturate good with 5mA from a 1k load.
are these correct? i copied them from urs explaination. is there anything to be explained with this circuit?
edit:
1. what is the purpose of the 0.01uF capacitor from pin5 to GND of the 555?
2. why the 0.1uF capacitor from pin3 to GND at the LM393 can stop it to amplify other noise and its own noise and stop oscilating?
3. what's the different between a comparator and operational amplifier? can a comparator be an op-amp and vice versa?
thanks for helping..
i'm going to do presentation with this circuit 2 weeks later. if anything goes wrong, correct me ok?
The 555 timer produces a 10kHz(approximately) squarewave output at pin 3 with the combination of R1, R2 and C1. The 'antenna' will produce electromagnetic field on and off in 10kHz.
the resonant frequency of the tank circuit is 10kHz. the 100K resistor creates a gain of a few hundred thousand which is so high that it probably amplifies its own noise and any noise that is around. It might even oscillate.
If a 0.1uF capacitor is added to ground at pin 3 then it won't oscillate. When the signal is received then the output of the receiver should alternate between 0V and Vcc at the frequency of the input. With a 5V supply then the output's min current of only 6mA should be able to saturate good with 5mA from a 1k load.
are these correct? i copied them from urs explaination. is there anything to be explained with this circuit?
edit:
1. what is the purpose of the 0.01uF capacitor from pin5 to GND of the 555?
2. why the 0.1uF capacitor from pin3 to GND at the LM393 can stop it to amplify other noise and its own noise and stop oscilating?
3. what's the different between a comparator and operational amplifier? can a comparator be an op-amp and vice versa?
thanks for helping..