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I really need your help!!!

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New Member
I'm working on my own project: automatic tap. When we put your hands in the sink, the tap automatically turns on and the water flows. One of my goals is that, sensor is as cheap as possible. So I decided to use IR sensor (the cheapest way!!!).

- The IR sensor comprises 2 modules: The transmitter and The receiver. When I designed the transmitter, I wanted to send our modulated signal to make the information signal immune from noise. The carrier signal frequency is 40 kHz and the significant signal frequency is 40 Hz. To modulate the signal, I used 2 IC NE555s, the first one produces a signal at frequency of 40 Hz and the second one produces a signal at frequency of 40 kHz (pin 3 of one is connected to pin 4 of the other).

But I'm in trouble. At the receiver, I want to use IC (3 pins) SFH-506. But I do not know how it work (When it receives the signal from the transmitter, What is the shape of signal at the output of SFH506? a pulse or a line? etc.).
One of my friends recommend me to use LM567, a tone decoder, The output of SFH is connected to the pin 3 of LM567. Exactly, I don't know why to connect like that. And also, I do not know how it work too (plz, do not laugh, I'm just a novice).

By the way, I've heard about solenoid valve. I have to use it to open the tape electrically to make the water flow. I have'nt seen it. Can some one give me some links to it. And explain to me how it work!

Can some one help me explain how SFH506 and LM567 work?
Can you introduce me some circuits that related to or useful to me and my project.

Thank you in advance!


New Member
When I was a student my "teacher" suggested this as a course project,
it is not just about electronic solutions it is about good design.... 8)

Things to consider.
What kind of sensor to use ? Break Beam, Reflective, Pyrolectric,Ultrasonic
How are you going to mount the sensor
Solenoid valves (found in automatic washing machines) have only two states of operation, fully open and closed.

Infra red reflective sensor circuit


New Member
You can get an IR ranging sensor in a complete package that has modulation and demodulation built into already. It will provide an output HIGH anytime an object is in front of it.


If you want to build your own circuit, change the output frequency to 38kHz and use this off-the-shelf IR sensor/demodulator. It will also provide an output HIGH anytime 38kHz light from the emitter reflects off an object (e.g. someone's hands) into the detector.


Once you establish the output from the sensor, connect as shown below. Use a MOSFET instead of the 2N2222 transistor if the solenoid draws more than 600mA.


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