Need advice on choosing RF module for sensor interfacing

[UroBoros]

I have to interface some proximity sensors and other sensors to my main Microcontroller CU unit. I am willing to place small MCU in each sensor location so that any type of sensor can be interfaced. But my confusion is regarding the type of RF modules suitable. My environment is very noisy and dusty. enclosures can be arranged, no problem. The distance I need is not very high maximum 50 meters and mostly can be considered as in open space. means in two big trucks with earth drilling machinery parked together. So vibration noise dust and all are there. But not too much distance. Reliability and cost seems the main issues here. I have searched different types the new LoRa seems to be costly and used for long distances.
So could you please suggest some RF modules which will be suitable for my purpose , so that I can narrow down the options and buy samples and start testing?

Thanks

 

[esp1]

hi U,
Check out the HC12 transceiver modules, they have a claimed range of 1000mtr line of sight, 100 channels available, using RS232 serial protocol for data, lost cost on eBay.
I use these modules with PIC's and Arduino PCB's
E

 

[betwixt]

esp1 - you should point out that only one of the 100 channels can be used at a time and only one is actually legal to use in most countries.

Brian.

- - - Updated - - -

esp1 - you should point out that only one of the 100 channels can be used at a time and only one is actually legal to use in most countries.

Brian.

 

[esp1]

hi Brian,
Would you please post a link to the site which shows/states the channel use limitations for the 433mHz band.?
All the information I have read says that channels 1 thru 69 are available for use by the UK hobbyist, when using the Hc12 modules, no reference to using only one channel.

Eric

 

[betwixt]

The spectrum allocation is somewhere on Ofcom's web site, I don't have the URL to hand but beware, it runs to many pages and covers almost DC to light!

As far as I'm aware, the only frequency available for use without permission is 433.920MHz with acceptable sidebands of course. In practice, I have several modules here which are locked by resonator to 433.92 but the actual transmission frequencies are as far away as 434.20MHz. These are supplied from the UK manufacturer and are not 'B' grade or copies. They use 13.56MHz resonators and PLL multipliers inside TDK5100 ICs which are also used in most similar devices.

Brian.

[Edit]
The information is on page 19 of the document "IR 2030 - UK Interface Requirements 2030 Licence Exempt Short Range Devices" from Ofcom. You need to read it in conjunction with the EN 300 220 specifications to see what category of transmission it refers to. Note that the latest release of the document is June 2014, the rules were different in earlier editions.

 

[FvM]

434 MHz band usage in the ETSI domain (e.g. UK) is specified in ETSI EN 300 220-1, permitted frequency range is 433.050 MHz to 434.790 MHz. No chanelisation defined.

 

[UroBoros]

Thanks for the info. Any way I think in the worst case I can even manage with a single channel. Few sensors only and I can poll them i round robin fashion. So channel availability is not an issue. (Correct me if I am wrong).
btw I am going to use this in India. Any idea about where I can find the legal info for India?

HC12 modules work in the 433Mhz band. I have some microchip modules in stock (MRF24J40MA) which works in the 2.4 Ghz band. May I know what is the difference or criteria in selecting the band for which we are going to choose the transceiver?
Microchip modules are more costly. But any advantages over this?

 

[betwixt]

There is little advantage in one frequency over the other as far as carrying data is concerned. The 433MHz frequency is shared with remote car locking devices, remote weather stations and even some heating and air con systems so it tends to be a crowded frequency. Even here in a very isolated location my receiver can pick up transmissions every few seconds.

If you need an antenna to improve range or eliminate interference, the one for 2.4GHz will be much smaller (about 20% of the size) so it may be more practical to install if one is needed. I haven't used the MRF24J40MA but similar devices from Nordic (nRF24L01 for example) have transaction management modes, they talk back and forth to confirm the data was received correctly and automatically resend if an error occurred.

Brian.

 

[UroBoros]

The HC12 I have not used, but I have tested MRF24J40MA. Not serious testing but it has got its own correcting mechanism and all. Its own PCB antenna and inside building very low range only. Not sure about it. my colleagues did it. Anyway I will test this HC12 also. HC12 seems half the prize only approximately, here in India. My data is small and I think if CRC fails I will have time to retry. My application needs not be very fast in data transmission.
Regarding the range which band should be better for range?
Any idea how much range **broken link removed** can expect indoor and outdoor practically?

 

[esp1]

hi UB,
This link will give you some useful information for the HC12.
https://www.allaboutcircuits.com/pr...enting-the-hc-12-wireless-transceiver-module/

E

 

[UroBoros]

Thanks for the details.
On a final analysis there is not much prize difference between Microchip 2.4 GHz unit and this one . The range I need to check both once again.
This page has got some more info about range of HT12

Thanks again