Would like to use an Arduino to read the temperature and humidity inside a grain bin. The sensor will probably need to be located approximately 100ft away from where I want to stand to read the data. What is my best option in completing this task? Every temp/humidity sensor I find has a cable length of 1 Meter.
You could go wireless. The parts to do so would probably be cheaper than 100 feet of wire. A Nano with, say a HC-12 transceiver on each end for instance.
I understand 1M would not even go 1/2 way through the grain bin. You can splice cable onto them to make longer. If these are critical parameters you might want to consider commercial units designed for your application. Your local farm store would be able to help. If these are generally for your edification The arduino will work because you can still validate the readings until you are comfortable with them. Do you even have power near the grain bin? If not can you run a 4 conductor low voltage wire from a place where you can get power, if so it will not be to difficult. My preference would be CAN but RF would work as well. Either way you will need an Arduino on one end sending data and another on the other to receive and display it. Now if you want to add another unit say a sylo you only need to add one unit with CAN, just splice the four wires.
For good reason, although 1m is a bit harsh. Long lengths can incur noise and signal loss are much better avoided. See above. You can get DS18B20 sensors with 5m cable. The problems associated are reflected in the price.
Inside grain bins are maybe a hazardous area in that the grain dust is explosive .
You need to check that out before going any further . Intrinsically safe equipment maybe needed .
Grain bins are also one of the most dangerous environments to enter .
RS485. There are sensors that come with that interface.
Grains bins are very dangerous. which is why I would like to create a temp sensor/humidity sensor. That way I don't have to climb in them all the time. And yes grain dust is explosive, but as long as the Arduino is outside the bin it would be fine.
I think you need to look up “ intrinsic safety “ . Just because the Arduino is outside is not sufficient to make things safe . You need to know what you are doing - safety barriers , zoning etc are a few things to look up .
As you think putting the Arduino outside is sufficient you should NOT do this project
Quote:
“ Risk of explosion:
Temperature monitoring therefore plays an important role in this type of storage. ATEX approval is required for the temperature sensors used. Due to the dusts present in grain silos, they are considered potentially explosive areas.”
The industry standard for grain bin temperature and humidity monitoring is one wire sensors. They can run on parasitic power and can have buses with a couple hundred sensors spread out over several hundred feet. If you are trying to monitor the temperature in grain bins to prevent spoiling I would recommend several sensors spread out along a cable that is hung down the center of the bin.
The standard temperature sensor would be a da18b20 if you also want humidity you need a Ds28ea00 with its 2 io connected to a sht15 humidity sensor. Basically each sensor has 2 bytes of user programmable memory that can be used to assign a cable I’d and a sensor number. So basically you write a sketch that reads any unread sensors and then you parse the data into an array. To get humidity you basically bit bang a clock and data signal over the two io using Matt Reiner’s library.
Safety wise really isn’t a concern. These cables deal with very little current and you would have to do something stupid to catch them on fire. Plus you should build some sort of protective sheath that covers your delicate sensors to protect them from damage.
Check out the combine forum, their is lots of talk on diy grain bin monitoring solutions and a question posed their will garner more useful replies. I will attach some links below. If you have any further questions feel free to ask.
From a lecky that once worked in coal mines, a statement like that shows very little knowledge on potentionally explosive environments.
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I have worked on a farm my whole life and I am not saying that it isn’t a dangerous environment, I am saying that the cables aren’t a source of danger. Even commercial cables are sometimes just sealed with heat shrink tubing. Nobody has blown up a grain bin because of faulty temperature cables.
Industrial 4-20mA sensors. Distance don't make a problem.
You really need to understand the dangers in what you are saying , you clearly don’t understand the concepts of intrinsic safety and limiting both voltage and current into a hazardous area , even if there is an electrical fault . These requirements have legal standing .
The consequences of an “ event” by your interventions could well bankrupt you for life or put you in prison , especially now you’ve been told on this forum , so you know !
I am not that afraid of blowing anything up because it isn’t really a problem. With one wire sensors the current is limited by the output pin on the arduino. I am not the first to place sensors or electronics into grain bins. If you properly protect the sensors you will not have a safety problem. Tons of farmers have built diy electronics for grain bins and stuff like this hasn’t been a problem.
If the Arduino power supply failed , or someone put a wire in the wrong place during maintenance you might get mains voltage on a pin , what then ?
It’s the same as saying I’ve never killed anyone by exceeding the speed limit. Maybe not , but if you did the consequences are high.
Standards relating to electrical installations are meant to be followed .
I’m “out” .
You could also argue what if a bearing on the center unload fails and sparks? Or if any piece of spinning metal in the bin sparks? Hell, look at a grain dryer. Grain bins aren't a safe environment and an Arduino is the least of your worries. But a homemade temperature cable isn't going to be a whole lot less safe than the light-duty commercial cables available.
I could also argue that if you are doing maintenance in your house and you connect a wire wrong you could kill yourself or burn down your house.
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