Arduino UNO - Smoker design, radio communication, temperature reading

Hello.
I am asking my colleagues for help in choosing a radio system or proposing an alternative solution for a backyard smokehouse.
The project consists in reading the temperature inside the smoking chamber, which is 20 / 30m away from the single-family house. In the future, I also want to control the smoke stream with a stepper motor. I would like to make the project as two modules (2x arduino) in two versions:
a) at home: Arduino UNO + LCD + TRANSCEIVER RFM73 / S (communication)
in the smoker: Arduino (UNO or nano) + DS18b20 (temperature sensor) + RFM73 / S + (or motor control, smoke outlet)
b) all the same, only communication takes place on the 30m cable between the Arduino.

In the case of radio communication, the signal will have to overcome two thick walls, unless some external antennas are used, then the antennas would be in their field of view.

Please give me some suggestions.

2.4GHz modules with PCB path antennas have a small range and the signal is unlikely to pass through the walls. For example, nrf24L01 + for PLN 5 does not even want to connect to one good wall, and with the visibility of the antennas 20-30m it is a good result. Transmitter power set to max, speed 250k / 1Mbps. 2Mbps is even worse, which is understandable.

Better idea about 433 and even better 866MHz, with Chinese 433 transmitter and receiver modules (or 315, but this is the band reserved by NATO) are very cheap, at the expense of having to write radio broadcast support. They are "stupid" and the receiver collects everything from the ether between 250 and 500MHz. The range through the walls is much better. Tested in old buildings, brick, from the basement to the second floor, connection stable. With one-way communication it is enough, the cost of a few zlotys plus the time wasted on writing the transmission protocol.

433/866 transceivers take care of the transmissions themselves, but are more expensive (PLN 20 / unit).
In both cases, you should connect even through the walls, which will save you installing antennas, so it's worth it.

To what extent does the temperature change in this smokehouse?
How exactly does it need to be measured?

niveasoft wrote:

If you write in Arduino, VirtualWire library handles it. Look on Google. The complete tutorial and explanation of the functionality are included.

Have a nice day

Thank you, and I used someone else's thread
This library has better code than mine because it encodes 4/6 bits and has a longer preamble, so I'll start using it.
I have not analyzed the code yet, as is the case of transmission sampling synchronization, i.e. whether the level or the slope is read. I only checked that it works stably at 2000bps.

In my code, I used a preamble to catch synchronization for the whole frame, but due to the instability of the period in mini-modules 433 (despite the stable input signal), it was able to travel in time with a longer frame. Maybe 4/6 prevent it. The same on the cable worked perfectly, of course, the radio receiver, however, has an unequal delay in the output from the transmitted signal. At low speeds it doesn't matter, above 1000bps it does.
By the way, if someone was curious, the Chinese modules work up to about 9kHz on the input, so what the author of the library gave is true. 8000-9000bps is realistic for short distances and 5000bps is stable for longer distances.

It's a fairy tale for pennies, and 433MHz can be easily amplified with an integrated hybrid UHF amplifier up to 15W for less than PLN 100, with a single 12V power supply Only the regulations do not allow you to speed up ...

TvWidget wrote:

To what extent does the temperature change in this smokehouse?
How exactly does it need to be measured?

Until there is no control, the temperature in the smokehouse should remain at a certain constant level, depending on smoking, from 20-90 degrees C. Unfortunately, sometimes when the wood substrate is too much you can see the flames, so the temperature is much above 125 degrees Celsius, which is beyond the capabilities of the DS temperature sensor. I want to put two such sensors in the smoking chamber and average the result.

And did anyone send the signal to the arduino via a cable (e.g. twisted pair) at a distance of 30m? Are there big losses?

hose2222 wrote:

And did anyone send the signal to the arduino via a cable (e.g. twisted pair) at a distance of 30m? Are there big losses?

I would not risk directly from the system legs, because even if the signal levels are sufficient with slow-changing signals (steepness of the slopes, oscillations), remember that the twisted pair behaves like an antenna when it is not sent a differential signal (and this is the idea of twisted pair). In addition, atmospheric discharges are likely to be used by the microcontroller ports.

The easiest way is to use translation circuits to RS323 levels (e.g. MAX323), and even better to RS485, and you can achieve much longer distances.

jackobi7 wrote:

hose2222 wrote:

And did anyone send the signal to the arduino via a cable (e.g. twisted pair) at a distance of 30m? Are there big losses?

I would not risk directly from the system legs, because even if the signal levels are sufficient with slow-changing signals (steepness of the slopes, oscillations), remember that the twisted pair behaves like an antenna when it is not sent a differential signal (and this is the idea of twisted pair). In addition, atmospheric discharges probably affect the ports of the microcontroller.

The easiest way is to use translation circuits to RS323 levels (e.g. MAX323), and even better to RS485, and you can achieve much longer distances.

I have a MAXIM MAX232CPE chip at home. Can I use it and it will run on 30m?

Quote:

I have a MAXIM MAX232CPE chip at home. Can I use it and it will run on 30m?

It should work at low transmission speeds, just don't forget you need two of these, at both ends

jackobi7 wrote:

Quote:

I have a MAXIM MAX232CPE chip at home. Can I use it and it will run on 30m?

It should work at low transmission speeds, just don't forget you need two of these, at both ends

Heh, yes I have two ;)

What is the best cable? UTP twisted pair, telephone?

Quote:

What is the best cable? UTP twisted pair, telephone?

Both should be equally good. Remember that you will not use the advantages of a twisted pair in this case, because it is not a differential transmission.
Shielding sooner might help, but if you are satisfied with speeds of 1200bps or 9600bps, then any cable should be good enough at 30m.
It's best to do a test, take a section of the cable, connect two MAX232s with it, put a pare kHz square signal on the input and watch what is output on the other end. I just don't know if you have tools for this (oscilloscope or logical analyzer - even a cheap Saleae for PLN 30 will be too much, and you can make a generator for 555).

Hello, if you want, I can send you a sketch of the receiver and transmitter on RF to PW, it seems to me that after small modifications it will be good for you