Hi, I stand before the question of whether the two sensors can communicate with one to another.
I try to set one sensor to sending and another sensor set to receiving. But i can't capture any signal on the receiver.
Please can anybody tell me if this is feasible. Thanks a lot.
You didn't provide a link to that product!
If it's the distance measuring sensor that Google finds I guess that the onboard electronic does ensure that your "communication trick" does not work. The sensor will listen for an echo only during a short time after it has sent a signal. That's only guessing as I don't know exactly how that sensor works.
It depends on what you mean by "communicate."
If you trigger them both at the same time, then when unit A receives the signal from unit B, it will tell you the half distance to unit B (and vice versa).
Unfortunately, if unit A happens to receive a reflection from its own signal before the signal from unit B arrives, it will tell you the distance to the reflecting object, not unit B.
If you only need "one way" communication and don't need the sensors to be waterproof, then you can fix the reflection problem by using HC-SR04 sensors and removing the transmitter transducer from the "receiving" unit.
Hello,
link to the sensor: ultrasonic-sensor
And my use-case is: Use first sensor for send frequency to second sensor which is set up only for listening.
Second sensor be some-how (for now i dont know how) in water with battery (again i dont know which one) and will waint for signal after it receive signal will do some operation. First sensor will use for send some frequency signal to the first sensor. So first sensor will communicate to the second sensor. And the communication will be maybe realize with FSK.
So for now:
I have two this sensors, the first sensor produce some signal every 4 milisec and the second sensor only listen.
For inspiration i look at NewPing libraly to know how to set up sensors only for sending and only for listening.
But for now it doesnt work 
You are proposing to use that distance sensor in a completely non-standard way. Good luck with that.
In post #2 I told you the easy way to set up a sensor to be a "receiver" (trigger transmitter and receiver at the same time). But if they are underwater and not connected by wires, good luck with that.
Another way to make a remote receiver would be to poll the output of one of the amplifying op amps downstream of the receiving transducer. That can be done with the HC-SR04; I don't know if that could be done as easily, if at all, with your sensor, with its one transducer. To do that, you would need to understand the schematic and operation of your sensor. And you would need to have the skill to solder a connection to the proper location on the PCB. Polling the output of an op amp wouldn't give you any distance information (unless you knew when the transmitter sent its pulse), but it would let you know that the receiver had received a signal from somewhere (or noise). Good luck with that, too.
DaveEvans:
You are proposing to use that distance sensor in a completely non-standard way. Good luck with that.
Yes you are right 
, i want to use this sensors for sending and receiveing some frequency signal based on FSK.
I guess this sensors when received any signal (noise you said) send true to the input pin.
But i dont know if is there any synchronization during triger and echod signal :(.
Do you know any other possibility?
lukasSirh:
But i dont know if is there any synchronization during triger and echod signal :(.Do you know any other possibility?
Another possibility was described in my third paragraph in post #4.
i want to use this sensors for sending and receiveing some frequency signal based on FSK.
You could use the transmitter and receiver piezo elements, but for FSK signals, you will have to design and build all your own electronics.
Seems like a sort of OOK might work...
a. IF the device can be hacked to make a transmitter that can send the normal 8 pulses at any time (and not wait for an echo), and
b. IF it can be hacked to make a receiver (by the method mentioned in the 3rd para above in post #4).
After some initialization/synchronization transmission, to tell the receiver to get ready, then communication begins at regular intervals, where a train of pulses = 1 and silence = 0.
If slow OOK would ok, the hack mentioned in a. might not be necessary: would have to wait for the transmitter to time-out (from not receiving an echo...about 38 ms) before transmitting again. That would control the interval timing.
DaveEvans:
Seems like a sort of OOK might work...a. IF the device can be hacked to make a transmitter that can send the normal 8 pulses at any time (and not wait for an echo), and
b. IF it can be hacked to make a receiver (by the method mentioned in the 3rd para above in post #4).
So do you mean that the device must be "physicaly" hacket? As i wrote i used NewPing library for inspiration.
So i use some code from boolean NewPing::ping_trigger() for "transmitter".
And receivers input set up to listenig view digitalRead() arduino nativ method.
DaveEvans:
Another way to make a remote receiver would be to poll the output of one of the amplifying op amps downstream of the receiving transducer. That can be done with the HC-SR04; ....
But i need waterproof device. On the other hand its may be good proof of concept.
lukasSirh:
Second sensor be some-how (for now i dont know how) in water...
lukasSirh:
But i need waterproof device.
What do you mean by "in water"? Do you mean: (1) below water, as in "underwater" or (2) in water, as "in a boat and might get splashed or occasionally wet"?
DaveEvans:
What do you mean by "in water"? Do you mean: (1) below water, as in "underwater" or (2) in water, as "in a boat and might get splashed or occasionally wet"?
I mean in water as "underwater".
Does this sensor work (in the normal way, as a distance sensor) underwater?
For ultrasonic transmission to work in water, you must use a transducer designed for working in water.
They are quite expensive.
DaveEvans:
Does this sensor work (in the normal way, as a distance sensor) underwater?
I dont know now 
i just try it at my desk, but according documentation this sensor might work underwater and like waterproof distance sensor.
I try it at my desk at first because i need proof if those two sensors can communicate between each other.
lukasSirh:
...according documentation this sensor might work underwater...
I'm skeptical. Please provide a link.
Ups i can't found documentation, but in every ebay, aliexpress, etc... and there is mention about waterproof.
"Waterproof" does not necessarily mean "works when submerged."
This paper seems to suggest that the JSN-SR04T will work when submerged.
Load up the NewPing library and the simple example sketch. Get the sensor working reliably in air first. Then find a body of water (such as a swimming pool or small boat harbor) that is approximately (30 to 40 cm x speed of sound in water / speed of sound in air) deep. Submerge the business end of the sensor a few cm deep and point the sensor at the bottom. If testing in a swimming pool, keep the sensor a meter or two away from the walls; if in a harbor, keep the sensor away from boats, piling, etc. Measure the depth with a tape measure, too (attach a weight to the tip of the tape if needed). Please report the measured depth and the sensor readings here.
I agree, do the test and let us know if it works!
This paper seems to suggest that the JSN-SR04T will work when submerged.
"seems to suggest" is an interesting and appropriate choice of words.
I looked through that thesis and decided that very little of it can be believed.
Figure 4.2 shows extremely noisy and unconvincing depth information in one dimension along X, down to about 70 cm, and the so-called 3D reconstruction is obviously just the 2D data simply repeated along the Y axis.
A much more interesting project is the autonomous lake mapping boat Sea Renderer, which uses the professional Airmar DST800 underwater transducer (cost about $270).
Such a transducer is required for efficient sound energy transfer to water, which has acoustic impedance about 3500 times higher than air.
jremington:
"seems to suggest" is an interesting and appropriate choice of words.
Selected with care!