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ryanleung
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Posts posted by ryanleung
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Maybe the phototransistor is being saturated by visible light. Is the range better when it is dark?
Yes
And I have a some question to ask you. My oscillator can not adjust the frequency to 38kHz. I use 220nF capacitor and 180uH inductor and I can not decrease the frequency anymore. -
How can i increase the transmit distance?
now, it can work 6-8 inch only -
The circuit can sucessfully received the signal. If I want to add the Automatic Gain Control(AGC) to the receiver, how can I do????
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The red circle voltage measured is not 5.9V, it is 9V same as the VCC
Is it no current though the IR LEDs?
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Ok, I will try it.
thanks -
how about the distance, the signal is very weak
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hello audioguru~~
I have are few question about my project.
1. I constructed your receiver already. And I amplified the signal using opamp, then it was connected to the audio amplifier. But the sound is very weak. I try to adjust the volume but the sound is also weak. I don't know how to increase the signal. And the maximum distance only have about 5cm that is very short.
2. I constructed the envelope detector (R=40ohm, C=0.1uf) and connected to your receiver output but the envelope detector output have not output signal.
thanks -
The resistor is 40ohm and the capacitor is 0.1uF. The frequency is 38kHz.
Is it right?
f=1/(2*pi*R*C) -
should I amplify the signal again?(tansmitter and receiver)
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Your IR receiver probably has a strong output at 38kHz now but you can't hear a frequency so high. Therefore the receiver needs to feed an AM detector diode and filter to recover the modulation.
The transmitter circuit has two very important resistors that need adjustment. See my sketch.
You are using Amplitude Modulation. Noise is fluctuations in amplitude that the circuit is designed to receive. You should be using FM instead, for low noise.
two resistors?
the AM detector means the envelope detector? -
Hello audioguru,
I constructed your transmitter and the receiver circuits already.
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hello audioguru.
My AM transmitter output signal is 9.2Vp-p. And I changed the R1, R2, C and R3 to 2.7kohm, 10kohm, 0.01uF and 1Mohm.
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I think the base of the oscillator should be modulated then it can connect to a common-emitter LED driver transistor.
An oscilloscope will show you what the transmitter is doing.
sorry, I don't know your mean. can you draw a circuit to me, thanks!!! -
umum......
How can I modify it now?
Thanks -
oh....sorry.....
I have some question about my transmitter.
I constructed the receiver already and I used the remote control to test the receiver. The receiver can receive the signal. If I used my transmitter to transmit the AM signal, the receiver can receive the signal but the signal is small. how can i modify the transmitter? the input signal only have about 1Vp-p, should i amplify the signal first?
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ok
thank you~~~ -
how to check the opamp which can satisfy the 38kHz operation?
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I used two IR LEDs already.
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1. can I change the value to R1 =100kohm ,R2=2.2kohm,R3=1Mohm and C=0.01uF???
2. can i use the TL072?
3. should I construct the band pass filter to filter the fluorescent light and the noise? -
I connected the pin4 to ground already and the signal was amplified. The problem occur at receiver or transmitter? Or the output power of the transmitter insufficient?
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R1 = 470ohm; C1 = 0.1uF; R2 = 1kohm; R3 = 10kohm; IC = LM324
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but my project requirement must use AM to transmit the audio signal. How can i amplify the power and increase the distance???
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Sorry, this circuit is old version. I changed the frequency to the 38kHz already. But the distance between the transmitter and the receiver is very short. How can i increase the distance? increase the power? I don't know how to increase it.
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I would like to use this circuit to transmit the audio signal.
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