# Show distance between two NRF24L01

Hello,

I would like to show on LCD the distance (in meters) between receiver and emitter NRF24L01 or GWB T400 Can somebody help me with fonction, please.

Attach GPSs to the Arduinos, and use the NRF24L01s to exchange the GPS co-ordinates between the two devices and calculate the distance between them.

That will work outdoors.

Kayumba: I would like to show on LCD the distance (in meters) between receiver and emitter NRF24L01 or GWB T400 Can somebody help me with fonction, please.

This comes up regularly. It's just not possible without extra hardware such as a GPS or a tape measure.

...R

If you know the frequency, would it not be possible to estimate the distance by measuring how long time it takes for a message to be send back and forth between the two devices?

Danois90:
If you know the frequency, would it not be possible to estimate the distance by measuring how long time it takes for a message to be send back and forth between the two devices?

Letâ€™s assume that the 2 devices are 10 metres apart. How long will it take a message to be sent back and forth ? Could you measure that with an Arduino ?

Danois90: If you know the frequency, would it not be possible to estimate the distance by measuring how long time it takes for a message to be send back and forth between the two devices?

It takes 0.033uS for a radio wave to travel 10m, what method would you suggest of timing to that resolution with an Arduino ?

There are 2.4Ghz devices that will measure time of flight, but they have specialist internal hardware. The SX1280 LoRa device has such a capability, read about my adventures with it here;

https://github.com/LoRaTracker/SX1280_Testing

UKHeliBob: Let's assume that the 2 devices are 10 metres apart. How long will it take a message to be sent back and forth ? Could you measure that with an Arduino ?

You could count how many messages you can send back and forth in a timeable period and do the math from there.

EDIT: That won't work, it would be limited by the arduino's frequency anyhow.

Thanks to every one.

I would like to make a reproduction of "Mandalorian Yoda tracer". Thats blinks faster when the emitter is closer etc. If some one have idea how to make it better ?

Danois90: If you know the frequency, would it not be possible to estimate the distance by measuring how long time it takes for a message to be send back and forth between the two devices?

The velocity of a radio signal does not depend on its frequency.

Kayumba: I would like to make a reproduction of "Mandalorian Yoda tracer".

That sounds like something from a film. If so it is probably a special effect - some guy behind the curtain is turning a potentiometer to control the blink rate.

...R

david_2018: The velocity of a radio signal does not depend on its frequency.

True that is.. Speed of light, the electromagnetic radiation has..

A couple of ultrasound sensors (one transmitting, one receiving) could also be used, but this would neither be easy nor stable if things are moving around with obstacles in between.

A couple of ultrasound sensors (one transmitting, one receiving) could also be used,

Only if you can synchronise the time on both devices

UKHeliBob: Only if you can synchronise the time on both devices

Time is not necessary but you would need to announce the sound pulses through the radios.

If the NRF24L01 supports giving you an indication of the received signal strength, that could be used as a rough estimate of distance, but will be highly dependent on transmitted signal strength, antenna orientation, and obstructions in the signal path, etc.

david_2018: If the NRF24L01 supports giving you an indication of the received signal strength

It only returns two levels - high or low. Taken together with all the issues you mention it would be useless for determining distance.

...R

Hi,

Robin2: That sounds like something from a film. If so it is probably a special effect - some guy behind the curtain is turning a potentiometer to control the blink rate.

...R

Thanks for everybody.

If I can not get distance, maybe with one code we can make blinking led faster when the receiver are closer and make blink slower when its far. Or just some thing like to detect the right direction and it makes blink led faster. What do you think?

In order to detect whether the two systems are moving closer or farther away you need to know how far apart they are. Do you see a problem ?