hello, i just want to know if HC-05 can measure distance to other HC-05

If yes? how? can you provide me a reference or a way on how to do it?

All i know is RSSI can do it... but i dont know how to code and convert it.

I hope you can help me.

 

There are much easier ways to measure distance. Does it have to be bluetooth?

It can be done sure but it is not going to be easy. Bluethooth signal strength varies too much dues to environmental conditions. One of the things is the device itself. So to be able to measure accurately, you would need some other accurate method to measure the distance for calibration.

 

There are much easier ways to measure distance. Does it have to be bluetooth?

It can be done sure but it is not going to be easy. Bluethooth signal strength varies too much dues to environmental conditions. One of the things is the device itself. So to be able to measure accurately, you would need some other accurate method to measure the distance for calibration.

I want to use it in follow me, and i cant use GPS because Im gonna use it in indoor, also RF.

my last choice is ultrasonic but i want to try the Bluetooth because my cart has 2 option the follow and manual control. the manual control use Bluetooth.

I just want to less the materials Im gonna use

 

If you already have an existing device then the manufacturer would have used bluetooth in the automatic mode if it were feasible, wouldn't they have?

Those follow me carts are an accident waiting to happen. If I were a lawyer, I would specialize in trip and fall injuries from those. I would make a fortune.

 

I want to use it in follow me, and i cant use GPS because Im gonna use it in indoor, also RF.

my last choice is ultrasonic but i want to try the Bluetooth because my cart has 2 option the follow and manual control. the manual control use Bluetooth.

I just want to less the materials Im gonna use

I'm glad to see you staying with the project!.

Basically, I would say that the ultrasonic method has a much better chance of working than Bluetooth, but in the end, it is an empirical question.

Back up for a second and look at what you actually have to do to make a follow-me robot. A person wears a device that sends out a signal. The robot detects the signal, but, most importantly, has several detectors (let's say 3 of them mounted across the midline of the robot frame. By calculating which of the three receivers shows the greatest signal strength, you decide the direction of the person transmitting the signal and go in that direction.

So, you need a signal generator and multiple detectors and you need to detect signal strength at each of the detectors. You also need to make that determination quickly and accurately.

Yes, RSSI (Received Signal Strength Indicator), has been used for distance measurement. A typical case is with BLE beacons. But I don't know of any case where this has been used to accurately measure the kind of distances that you want in a follow-me robot. Look into what RSSI is and how it is calculated in a typical Bluetooth application.

You would need multiple BLE detectors and the person would be wearing a BLE beacon for example. With the right detectors, you certainly could get RSSI values from each of the detectors. It is doubtful that they would be accurate enough to accomplish what you want to do though - again, it is an empirical question.

As for off-the-shelf components, it becomes even more difficult. Locating where you are by BLE Beacon RSSI works in certain environments because the question is not really "where are you", but rather, "which beacon are you closest to" and the beacons are pretty far apart, so you don't need to have great accuracy.

As for HC-05, personally, I would not go that route at all. These device need to be connected, which is a whole other issue - even if you could get an RSSI.

Go back to your ultrasonic method.

An SR-04 ultrasonic module is a transmitter and a receiver. You trigger the transmitter and then start waiting for the receiver to detect the 40kHz wave, which it will do if the wave has bounced off an object. Because you know when the wave was initiated, you can calculate the distance traveled and the object's distance, pretty easily.

Consider an example of four SR04s - one is on the person to be followed and the other three are on the robot. The SR-04 on the person is used only as a transmitter (they are easy enough to trigger). The other three (on the robot) are used only as detectors, and they all start "listening" at the same time.. Spaced far enough apart, I think that they could possibly function together as a signal strength discriminator - especially if you programmed the robot to do a kind of a wiggle to hone in on a difference in signal strength - derived from the difference in detection time between the three receivers.

Go back and watch the video that I included in a previous response (and here below). That illustrates the method. You could start off with some stationary tests and the three detectors spaced very far apart as a test of concept, so to speak.

Finally, using RF is probably the best (but not off-the-shelf-Bluetooth or BLE), but you might have to do much more and know much more - on this point, there are others here who might well know about some off-the-shelf devices that could be adapted.

This is not so easy, but think of how cool it will be when you get it to work!