RF 433mhz or 2.4Ghz collision

Using Arduino Networking, Protocols, and Devices
1

Hi

Im quite newbie in arduino/electronic and im experimenting with a project where I need to have few battery powered transmitter transmitting to one receiver.

Im investigating a bit more over 433mhz or 2.4ghz and I though you guys can help me to guess if is a good solution.

I have this requisites.

  1. the transmitter should transmit at least 2 times per second
  2. the transmitter and the receiver should work between 10cm to 1.5m)
  3. In the commented range distance, can be around 4-5 transmitters transmitting at the same time (2times per second)
  4. The only comunication that they should do is send an ID to identify their self, like: 000001, 000002 etc... up to 5-6 aprox)
  5. the transmitter are battery powered and small, (a button battery?) and have a long life like 6month or 1 year,

I have several questions about if is no conflict with at least 5 trannsmitter trying to comunicate with the receiver saying "hello im 0000001". also the battery life of these devices with a button battery is gonna be good transmitting 2 times per second (max 1.5m range)

Thanks guys,

2

What do I get if I guess correctly?

Paul

3

I only have experience with the nRF24L01+ 2.4GHz transceivers.

I assume all 5 of your devices are intended to communicate with each other. if not, just assign different channels to the different pairs and there won't be data collisions.

If they are all to operate on the same channel and if you define one of them as master it would be easy to arrange for communication with several others without risk of data collisions - and at a higher rate than 2 per second.

I suggest extending the second example in this Simple nRF24L01+ Tutorial to communicate with several slaves.

...R

4

Robin2:
I only have experience with the nRF24L01+ 2.4GHz transceivers.

I assume all 5 of your devices are intended to communicate with each other. if not, just assign different channels to the different pairs and there won't be data collisions.

If they are all to operate on the same channel and if you define one of them as master it would be easy to arrange for communication with several others without risk of data collisions - and at a higher rate than 2 per second.

I suggest extending the second example in this Simple nRF24L01+ Tutorial to communicate with several slaves.

...R

All the transmitter should be sending his UUID to the receiver, and the receiver should in 1.5sec be able to see all the transmitters that just enter in range.

Basically, you will carry over you 3,4, 5 maybe 6 transmitters, and my receiver will be at the wall. when you walking next to the receiver, in a normal 1.5sec aprox that you will be in range (1.5m max) the receiver have to be able to see "00001" "00002" and "000003" are in range. (ex)

5

jjosealonso:
All the transmitter should be sending his UUID to the receiver, and the receiver should in 1.5sec be able to see all the transmitters that just enter in range.

Basically, you will carry over you 3,4, 5 maybe 6 transmitters, and my receiver will be at the wall. when you walking next to the receiver, in a normal 1.5sec aprox that you will be in range (1.5m max) the receiver have to be able to see "00001" "00002" and "000003" are in range. (ex)

That is all very interesting but it does not seem to take any account of what I said in Reply #2 even though you quoted my reply.

And the range of an nRF24 is probably 30 metres or more, not 1.5m. I don't think there are any wireless devices that can only be detected when they are at 1.5m or closer.

Why would a person have more than on transmitter on him/her ?

Will the base unit know the IDs of all the transmitters?
Or, more importantly, will every transmitter know the address or ID of the base unit?

You really need to tell us what your project is all about and not just little bits of the tech solution that you are thinking of.

...R

6

Robin2:
That is all very interesting but it does not seem to take any account of what I said in Reply #2 even though you quoted my reply.

And the range of an nRF24 is probably 30 metres or more, not 1.5m. I don't think there are any wireless devices that can only be detected when they are at 1.5m or closer.

Why would a person have more than on transmitter on him/her ?

Will the base unit know the IDs of all the transmitters?
Or, more importantly, will every transmitter know the address or ID of the base unit?

You really need to tell us what your project is all about and not just little bits of the tech solution that you are thinking of.

...R

Oh sorry, I was not clear enought.

Basically im exploring few technologies for my project and now im exploring the RF.

The project is about put RF transmitters next to equipments, attached to it (battery powered) they in theory will be transmitting his UUID only, and when a person is leaving the place, the receiver in the wall should be able to see the UUIDs in range and see that actually is taking all the equipments (all the transmitter are present).

Thats why the feedback have to be when leaving the door, thats why I should limit the range to 1.5m aprox or be able to filter or measure it.

Also im exploring if is a way to do 4, 5 or maybe 6 transmitter comunicating constantly to the receiver sending his UUID and dont have any conflict or collision?

I heard that will be collisions, and I heard about channels, Im starting to think if would be possible and fast enough to loop over the channels (10 channels is fine) and check if is somebody there broadcasting his UUID?

It mean that the receiver should loop over the 10 channels and check if is a broadcasting there and have a result over the 10 channels in 1.5secons aprox that its the time that can take a person to leave through the door.

7

Before you spend any time worrying about data collisions or the ability to detect N devices in T seconds you need to find a wireless device that does not cause unwanted detections when it is at (say) 2 or 3 metres distance. I don't think such devices exist.

Are you trying to detect if someone is stealing equipment?

Maybe you could use the sort of scanner they have at the doors of big stores?

...R

8

Thanks you guys. Really I appreciate your knowledge and experience.

I think then beacons Bluetooth is my tech. They use battery and are small and they are broadcasting few times per second.

Only using the discovery mode and the TX and RSSI calibrated people is doing well indoor positioning.

My only problem is that the world of Bluetooth modules is a mess. I bought few modules and still noone offer the features of beacons detection. Only hm-10 and have the problem of maximum 6 devices. Not even the nearest.

Any idea about a BT master/central with this requisites?