Dear,
i'm a newbie in arduino field and i have to use arduino uno in my graduation project which is how to prove doppler effect using trx. i searched for a trx until i found nRF24L01 which is a half duplex trx so i have to use 2 trx with 2 arduino uno boards. i knew that nRF24L01 is used GFSK modulation tech. which can help me to prove my idea. i think to send a continuous periodic signal generated from the uno to be received by the other trx connected to the other uno. i want to know is it possible to do that and if anyone can help me in the code please tell me.
this program is a periodic signal program written by me :
//4 sec per complete cycle (duty cycle 50%)
int PIN = 13;
void setup()
{
pinMode(PIN, OUTPUT);
}
void loop()
{
int state = 0;
while(1) {
if(state == 0)
{
digitalWrite(PIN, LOW);
state = 1;
}
else
{
digitalWrite(PIN, HIGH);
state = 0;
}
delay(2000);
}
}
is it right? if it is , is it possible to transmit continuously to compress if the moving object moves forward and expand if the object moves backward to prove the doppler effect.
BR.
I guess that 'trx' means transceiver. I don't understand what your idea is or how you plan to use a pair of nRF24L01 to prove it, or what problem you're asking us to help you solve in order to achieve that. Is the code you posted relevant, and if so - how?
Perhaps if you explained what help you're asking for, somebody might be able to provide it.
I have no idea how you would measure doppler shift in a 2.4GHz signal. I reckon you would need equipment that is a few orders of magnitude more sophisticated and more expensive than an Arduino.
As I understand it doppler shift affects the underlying wireless signal, not the data carried by that signal.
Those 2.4Ghz transceivers transmit and receive digital data as far as the users are considered. Users have no access to the actual wireless signal. The motion of one transceiver relative to the other won't be detectable in the data that is received - it will work, or it won't.
Does your project have to use a wireless signal or could it use an audio (or low ultrasonic) signal where the wavelengths are long enough to be measurable by an Arduino.
my project is how to measure distance using rf module and by applying doppler effect tech. and i found that if i use two nRF24L01 consider it a half duplex transceiver i can detect the direction but if i use four of nRF24L01 i can detect the distance. do u understand what i want to do ? can any one help me?
MOSFET92:
my project is how to measure distance using rf module
You've lost me there. How do you propose to measure distance / speed using the RF24 transceivers?
MOSFET92:
do u understand what i want to do ?
No, not a clue. I have no idea what you're trying to do, I have no idea how the Arduino features in your solution and I have no idea what help you're asking for to implement that. If you want any practical advice you need to provide a much clearer question, because so far it isn't making any sense at all.
Doppler effect is a method that used FSK modulation tech. that give a compression signal if the moving object moves forward to the source of the signal and give an expansion signal if the object moves backward from the source.
for the first phase of my project i want to only detect the direction of the object by send a train of pulses using nRF24L01 to detect the direction.
for the second phase of the project i want to do the same and when i combine the first and the second phase i can at that moment determine the distance.
each phase contain 2 of nRF24L01 because the trx is a half duplex transmit and then receive not at the same time so i use 2 of trx in each phase.
if i increase the number of phases, i can detect the accurate distance for the moving object in an area.
the 2 trx in each phase is located next to each other and i want to send pulses by the tx and wait the reflected signal from the object to be received by the rx.
finally, i want to know if i can send a train of continuous pulses using nRF24L01? and if the whole idea that i explained in this replay can be done ?
do u get my point nw?
MOSFET92:
if the whole idea that i explained in this replay can be done ?
Frankly no, what you're describing sounds completely impractical. I don't see any feasible way to use the nRF24L01 module to detect and quantify frequency shifts, and the whole basis of your approach seems to be unworkable.
Is a technique available for direction finding using a commutated antenna array which effectively traverses a circular path in the plane so that it alternately approaches and recedes from the transmitter. The resulting frequency variation is detected by an ordinary FM receiver as a frequency corresponding to the rotational speed and whose phase indicates the direction from which the signal arrives.
Given an antenna array of say, a meter in diameter, the effective velocity producing the Doppler shift is in the order of a kilometre per second and as the process involve an alternating shift, frequency accuracy is in itself, not a concern.
GFSK aside, I am not aware of any suggestion that the nRF24L01 is designed to quantitatively decode FM, let alone measure the base frequency precisely, so I cannot see how this would be of any use in whatever unexplained application is proposed here.
my project is how to measure distance using rf module and by applying doppler effect tech. and i found that if i use two nRF24L01 consider it a half duplex transceiver i can detect the direction but if i use four of nRF24L01 i can detect the distance. do u understand what i want to do ? can any one help me?
Looks like the nRF24L01+ can do "on device" frequency deviation measurements and much more. Get in touch with technical support at Nordic to see if what you describe by using multiple devices is possible.
"Note: The tests described in this document are intended for performance testing in the development stages of a product. Some of these tests can also be used during production testing while others are too complex and take too much time to be feasible for use in a production line."
MOSFET92:
Doppler effect is a method that used FSK modulation tech.
I haven't seen any reference to FSK in the Wikipedia article about Doppler shift and I have a sneaking suspicion that this is one occasion when Wikipedia is correct.
There may well be some technique that uses FSK and doppler shift to measure stuff, but calling that technique "doppler effect" is not correct. And, having said that, you have not described how your proposed system is intended to work. And without a description of how it is to work, it is hard to give useful advice.
I maintain my original suspicion that an Arduino and 2.4GHz transceiver are not suitable.
When you understand and can describe what you want to do (and if you still think an Arduino may be suitable) come back and tell us. I have no doubt that if it is practical there will be interested people here.