Hello guys!

I want to trasmit state of three signals through RF (10m distance) - power, fault1, fault2 indicated by leds. Transmitter - powered from 12VDC, receiver - led for each signal indication, battery powered let's say CR2032, or AAA battery or some small li-po.

My initial thought was to use those chinese simple 4ch modules running on 433mhz (SCT2260), but they introduce delay on the incoming signal, hundreds of ms. What is more, the power signal is transmitted almost all the time, so no other signal could be transmitted at the same time. However, I could opt out of using the power signal and live with the delays, but I started looking for a better solution.

My second thought was using microcontroller, some simple STM32 or ATMEGA with the nrf24l01 module. Would this allow for pairing the modules with some single button if I needed to use a couple of them in closer distance? Would this allow for transmitting multiple signals and reduce delay? I'm not sure if microcontroller is needed with this simple application for just transmitting three signals.

Any other solutions? I'm open for your suggestions.
Thank you!

 

NRF24 module is well working in 200-300 m distance but with duck-neck antenna up to 1 km, have high data rate, have small price of 0.99 $, small antenna at 2400 MHz but rather high energy consumption, factually transmitting 1 ms long "telegram" of telemetry data once a minute the battery gives 1 year of shift. LORA at 867 MHz have max distance up to 3 km with good antenna, what is 4x larger than NRF, much slower data speed, price is about 30x higher (at 20-30 $) and battery may serve up to 3 years at identical use. Both have absolute noise resistant, both use a multichannel async transmission of packets, having parity control, multiple repeating if needed, and stepwise power adaptation to environment noises.
Examples:
NRF024: https://www.ebay.com/itm/125666531891?itmmeta=01HQ32Y0B684BVRE48JVZHFZ30&hash=item1d424f1a33:g:Lp8AAOSwtihjnAjv&itmprp=enc:AQAIAAAA4Dza0qZZWcj8whYMTp+RCoOY7+JG6tJzejOcaD1RuyqLSZyJ+6uyv5/lvKFSUAs8kEP8NtVDRzGitf0zgD+9k/GTL1vhVibZBZQxrTO2n4uCiC0eGKFAtWxUWZlq9PnvSlQKcd8S2rK5ciw9RtpaFYCXeXCCecVx9Hrh/zrmGmnNzAtm5fjk00bRAGAT1+99ABAglz/ps4dIDpeG3W3fR98LI7VKGe+477bCcRCyB0BzRug0M9IpcBlaKNRjFpQ/0UE5OWljJ64dTRMNew08+xSo2g4eNl+71fSr5Mk0Lbmu|tkp:Bk9SR9SF-OK4Yw

LORA 868 MHz: https://www.ebay.com/itm/183931693105?itmmeta=01HQ32Z6HXQSBEQF89M0F8X55E&hash=item2ad32ee831:g:hggAAOSwwrFdZPgG&itmprp=enc:AQAIAAAA4IsS5WDOQ4FPhw/2E9y3cmAzZPJ0sLjt6eb1JhLuROyDXhcDRm6pOImA8O9LQxvr15mt5Cu2h31E2UJkdFSSKm9eCG7xpUirb8z7HggOX4r9AEQD81N7Tol63jn20V6m3OBP0vkIHvfvGZZlfsPy7nrEkPY9abxw7hwKcz7WGD25+J/30/bDOcimr7GB90V0vqdD+ID+5g28Yii/YrKRH2yCLQtEzz/9zbt7uPvI5SJjwm5bLk4AYEt23hd8g9Nov6CtoG+dFYZlzRymlCLurcWk8jnfSjFPU9VXbB9erHEz|tkp:Bk9SR4bp_OK4Yw

LORA 433 MHz: https://www.ebay.com/itm/204545007915?itmmeta=01HQ32Z6HXK0VWC228FV6W6K3N&hash=item2f9fd5212b:g:dwUAAOSwPRZlWAcH&itmprp=enc:AQAIAAAAwAnZ--vEdGr5Sr02JUd7A3a6ORaTESm592H2Jd62gOIzS4kR6dgANuxEtBBRMPDLznsjnnj28EhgkK9aw1BNkqhSLuuldbbxKTSlRkst1TOS6yyyeVzK7wGiN2oDFWT9MdiDtqUUlQ94n8m3DRzDD0VB81vShDJrf7els+i/ZNlw7F/BXX/9u03vt5ESveoLeH9HadZrUaf9JUvLSiE2Okc/yAGgQY5GinG2mQk5EebibG13egnJSW2XOEXqbmGmLg==|tkp:Bk9SR4bp_OK4Yw

Atmega module is inavoidable for as one, as another. You cannot squeeze without.

 

What is more, the power signal is transmitted almost all the time, so no other signal could be transmitted at the same time. However, I could opt out of using the power signal and live with the delays, but I started looking for a better solution.

Depending on where you are located you might not be able to use 433MHz for what you are planning to do because it would be illegal. In the US, the FCC regulations limit the length of transmissions and the total air time per hour. It is quite a small allowance.

Not only would your always on power signal be a problem, but constant status updates would also be a problem. Because 433MHz is an ISM (Industrial, Scientific, Medical) license-free band by international treaty, most countries will have similar limits, or a different band with those limits.

The nRF2401L is a good choice because it operates in the 2.4GHz band where constant transmission is not a problem. It also supports up to six data pipes which are virtual connections so you could easily run the power on signal continuously while still transmitting status changes as required.

If you do choose the nRF2401L, be aware that the antenna is critical, it must be resonant of the modules will just not work properly, Also, don’t buy the cheap ones, they are much more prone to radio problems.

Get an nRF2401L+PA+LNA version. These have a Power Amplifier (PA) so you can transmit up to the full legal limit is needed, and a Low Noise Amplifier (LNA) that will greatly improve reception, reducing the power you need.

Always use the lowest effective transmit power! Remember, you are on a shared band and can easily add to the interference that reduces effective data rates for others. Lower power also means less energy use.