Lowering cost of using NRF24L01 radio module for communication between several Arduinos [closed]

Question

I have several Arduino Uno's if I am using several NRF24L01 modules to transmit a simple pulse (1 bit of information which can be high or low) between them-from one Arduino to the rest of them. Then I was considering, because the information is one bit of information only can I replace the other receiving NRF24L01 module's with something cheaper (and probably simpler) ?-may something based on like a simple tank LC circuit?-or it maybe another simple circuit instead of the LC one. The intuition for asking the question is because only 1 bit of information (which maybe represented by a string of 1's or another known string X if it makes the decoding simpler) is transmitted then the receiving circuit maybe simplified somehow -rather than use something like the full circuitry of a NRF24L01 module. Elaborating further on a possible scheme for decoding X may be done by just counting the "marks ratio"-as done "in a marks and spaces style scheme"-e.g. if there are known ratio of 1's, than compared to the usual ratio, then we can consider that to be a high signal received -the number of 1s sent is such that the binary information from the NRF24L01 protocol, that sends X, would not significantly affect the ratio of the 1s. however I don't know how accurate my intuition is here.

So in a nutshell, I want to know if there is a simple circuit that does what I want - an answer may include a custom Arduino sketch suggestion for the transmitter and/or receiver.

Answer 1

To receive a signal from an nRF24L01 you either need another nRF24L01 or to reimplement the nRF24L01 in discrete components. That's a big, complex circuit requiring precision components and PCB layout. At 2.4GHz, with GFSK modulation, you need amazing skills to create something that would work reliably - and the cost would be astronomical compared to the cost of an nRF24L01.

Your thought that you are "only sending 1 bit of data" is completely wrong. Yes, you may be providing only 1 bit of data to the library that controls your nRF24L01 - however the nRF24L01 then encapsulates that single bit into a fixed length packet including source and destination addresses, checksums, and even implements a reliable ACK/NACK system for packet retransmission. None of that can be thought of as a "single bit" once it gets out onto the airwaves - so the system that you came up with would have to be able to interpret and handle that entire packet and provide any requested ACK/NACK signals back to the transmitter.

If you want to receive with a simpler system then you need to also transmit with a simpler system. The simplest system is probably the 433MHz PAM systems you find on eBay. You pull the input pin HIGH on the transmitter and the output pin on the receiver goes HIGH. You pull the transmitter pin LOW and the receiver pin goes LOW. (Basically you turn the carrier on and off at one end, and the other end tells you if the carrier is on or off - Pulse Amplitude Modulation [also known as On Off Keying - OOK]).

Coupling that with UART signals it's possible to send actual data, but if all you need is HIGH/LOW signalling then you can drive it direct with any GPIO pin.

They are incredibly crude, and would never pass any kind of emissions testing, but they get the job done at a very low cost.

While it may be possible to create a crude 2.4GHz PAM transmitter and receiver, owing to the broadband spectrum harmonics you would have unless you managed to produce an absolutely pure sine-wave with zero harmonic distortion, the interference it would cause to other devices nearby (such as your WiFi connection) would cause untold problems. No doubt your neighbours would have something to say about that - and maybe FCC / OFCOM / whoever.

Answer 2

I have several Arduino Uno's if I am using several NRF24L01 modules to transmit a simple pulse (1 bit of information which can be high or low) between them-from one Arduino to the rest of them.

Let us assume that the broadcast has to reach all. None of the listeners are allowed to drop messages. How would this be achieved? Each listener would have to acknowledge the message.

Anyway reasoning about the application requirements and communication protocol may help determine if a "cheaper" solution is possible.

IMHO using NRF24L01+ is a cheap solution in this scenario.

Cheers!