Temp Sensor

I have a work related project that I am interested in using an Arduino to accomplish with. I have about seven cold storage coolers in a warehouse. I would like to put remote LCD temperature displays in an office about 200'-300' away. I need to put a bank of 7 displays closely watchin temperature and maybe humidity on the coolers. I dont think a wireless system will work and I am not against running multiple wires. Any help would be appreciated. I need to know if I can use one Arduino card to display all seven screens or multiples. I also am interested in a higher resolution display if possible. Thanks

Reilly

what is the temperature in the coolers? what precision do you want? what accuracy?

the DHT11 / DHT 22 are simple to use nice sensors that read both temperature and humidity.

One Arduino can do 7 sensors, but note thatevery sensor needs GND, 5V and a data line. As GND and 5V can be shared that means 9 lines in total.

I would place one Arduino near the coolers so the wire between sensors board is (relative) small and let that Arduino send its data to another Arduino over RS485 as this is more stable for long distances. The second Arduino receives the sensor data over RS485 and displays them on a screen and can sound an alarm if temp is above a certain limit and log the temperature on an SD card etc.

in short :

sensor --(local) --Arduino1----------------------------------(RS485)----------------------------------------------------Arduino2--LCD

Coolers are between 32* and 75*. I would like them to be fairly accurate almost like a back up to what currently controls the refridgeration equipment. Which Arduino would fit my purpose best? Another question is what sort of cable can I run between the sensors/Arduino and between both Arduinos and the LCD screen. This is for show but also a secondary monitoring system so what sort of screen does the Arduino support? Thanks again.

@robtillaart

I have a "crazy" idea here... What about using fiber optics ? If the Ardiuno Sensor is sending only, one fiber wire can be use, and the circuit of a fiber optic transmitting is simple. ( a transistor control led ) , If you need two way communication, well two fiber wire will be use. The receiver circuit is simple too.

The Display adiuno ( the receiver ) can be code in a way, it tell which sensors and display the data.

My crazy ... idea...

I like the idea of fiber, but its such a distance I would imagine it would be a pretty penny to get 300'+. What would be other options for signal wiring? Thanks

The fiber idea is great !! checking which frequencies work / which receiver to use.

Another option for wiring is Internet over powerlines, also not cheap but it works very well.

Maybe someone can invent RS232 over powerline?

@robtillaart

Thank.

@reilly8282

Here a link of DigiKey for the fibre optics prices. In my opinion, it not that bad… http://search.digikey.com/scripts/dksearch/dksus.dll. The type of cable is the 1000 um type micro-meter or 1 mm type. with plastic coating, the size is about 2 mm. As for the transmitter and receiver, check IF-D92 - transceiver and IF-E92A - transmitter. Here the site of Industrial fiberoptics → http://www.i-fiberoptics.com/ and here my tread about the use of fiber optics. http://arduino.cc/forum/index.php/topic,89595.0.html

The raison I prefer fiber optics is : - not affected by electrical noises

  • simple to impliments
  • simple interface circuit

One Arduino can do 7 sensors, but note thatevery sensor needs GND, 5V and a data line. As GND and 5V can be shared that means 9 lines in total.

As robtillaart mention, my question to you : How far the sensors will be ( the 7 sensors ). The farther the sensor and the Ardiuno, the worst the reading will be. It is recommend the sensor wire be as short as possible. You may have to build 7 sensor-Ardiuno, and 7 cable to the main Ardiuno for Display and data processing. Or one sensor connect to an amplifier circuit - booster ( 7 booster in total ) using a telephone wire ( 4 conductors ) to a main amplifier / adjuster circuit to compensate what in vs what out. The Ardiuno - sensor send data in a form of protocol ( ex: start1-data1-end1-start2-data2-end2-…the rest ) through the fiber optic - one long fiber optic, the receiving Ardiuno will process and display the data.

Anyway, just brainstorming here…

Here a picture of the connector and cable I am talking about.

This is a warehouse roughly 300' across and the coolers line the front of the building except for maybe a 30' office space. I don't mind placing the arduino centered between the seven coolers but that distance could vary more than 100'. I am thinking a arduino with temp sensor per cooler communicating to one main arduino then across a fiber to another arduino that connects to seven LCD displays. Does that make sense? Do the arduino's perform well in temps down in the mid 30F's-40F's? Thanks for all the replies

couldin't you use 1 nano per cooler and have them wired in series. i.e. arduino(1) on cooler one would send temperature to arduino(2). arduino(2) on cooler two would send temperature data of 1 and 2 to arduino(3), etc. then you wouldnt have to worry about the primary/master arduino getting rx from 7 boards. just one.

actually... i guess it'll be a bit harder to code for but they have digital temp sensors for long runs: https://www.adafruit.com/products/381 https://www.adafruit.com/products/642 would be a lot cheaper. you'd only need one or two arduinos (depending on if you're going to run the temp sensor to the main board, or to a slave board that will transmit to the master)

as for the high resolution display. you could use processing to make a gui and display it at whatever res your monitor is. (i think... im just breaking the surface of processing right now). however this would require a host computer. (maybe a raspberry pi?) or possibly an android tablet?

@reilly8282

Well, here a picture of the block diagram of your proposal. I include some of my ideas in it. Like you said, a sensor / Ardiuno —> data through fiber, arriving to a 7 fiber receiver board with a de-multiplex ( 1 to 7 ) and an Arduino and re-send data with the 7 sensor data, going through fiber to a receiver, arduino or PC to display the data.

If every cooler has its own arduino, why not add a transmitter to do things wirelessly? I know you mention that you think it won't work but for what reason?

the sensor inside the cooler, the arduino outside with its own RF unit sending to the arduino that gathers and displays the data, possibly even with some warning (light, horn) when needed.

Do the arduino's perform well in temps down in the mid 30F's-40F's? Thanks for all the replies

It is possible...but I not sure.

It don't have to be an Ardiuno UNO board or Nano. It can be a simple stand alone ATMEGA328P, with the support compoments ( xtal, caps, reset circuit ), temp sensor connect to a analog pin, and the RX connect to a fiber transmitter circuit and including a 5 V regulator. With a nice seal box, and power can from a wall wart or unregulated PSU ( transformer, retifier, filter cap )

At that temperature you will have condensation - this is generally a no-no for any electronics so you will have to take precautions (a sealed or nearly sealed box ? - the heat generated by the electronics will help prevent 100% humidity inside the box... Also finding a cheap relative humidity sensor that works reliably at freezing point may be tricky perhaps? Might be a little specialised. Keep the temp sensor away from heat-generating electronics of course - perhaps a separate sealed probe.

@MarkT

I do agree with you. The Ardiuno ( with chip / regulator ) in a box may cause problems inside a cold environment. Maybe the solution is place the box outside the cooler, drill a hole, place the sensor wires and seal the hole with a sealer product ( glue or weather sealer ). The Arduino box with the fiber optic and power cable ( for the DC power of the Arduino Box ).

As for the sensor, I made a seal temp sensor using the LM334AZ and seal it into an aluminium tube.

Here the picture.

I didnt think the wifi would transmit very well through some of the metal seperator walls inside the building, its hard to get cell phone signal in some areas in here. The arduinos would be some distance apart and wasnt sure how strong the signal could be. Im just trying to lay this all out before I buy some of this equipment with company money. If I purchase things and they dont function properly it wouldnt look great on my credibility in the future. So I am listening to all the ideas, please keep them coming. Thanks.

@reilly8282

Can you drill a small hole for a sensor wire to go through inside the cooler ? If yes. You almost in the game...

Absolutely I can drill anything I need.

I forgot to mention... build a test unit system... A sensor + arduino + serial link with the PC using Serial.print() to check the sensor/arduino unit. If work. Build 7 of them with the sensor using my idea for the sensor. Metal is a good heat/cold conductor.

And experiment with a prototype if possible to test the system before the full instalation.

PS: I have a good idea of what type of wharehouse is it. I saw one of them when I was a truck driver with a reefer delivering cold products / meats.

Here the datasheet of the LM334Z. I did use it as a temp sensor. It need external circuit to work properly. I check the datasheet, on page 4, bottom left graph show a LINEAR graph Vout vs Temp in Celsius. The device has a 10 mV / Kelvin as a temp sensor. So by looking at the datasheet, you can figure out a circuit to output a voltage from 0 to 5 V for the analog pin depending of the voltage out / temperature of the LM334Z. And lower temperature is -50 Celsius. Just fine for an industrial cooler system. The accuracy of the sensor is 10 mV / Kelvin.

Here the site - datasheet : http://www.datasheetcatalog.org/datasheet2/9/0ozy8z2j6us7g86aiswt8djlc73y.pdf

Edit : Opps…Not the LM334 for operating around -40 C. It is the LM134 can operated at -40 C. I miss that part in the datasheet.

Techone: I forgot to mention... build a test unit system... A sensor + arduino + serial link with the PC using Serial.print() to check the sensor/arduino unit. If work. Build 7 of them with the sensor using my idea for the sensor. Metal is a good heat/cold conductor.

And experiment with a prototype if possible to test the system before the full instalation.

PS: I have a good idea of what type of wharehouse is it. I saw one of them when I was a truck driver with a reefer delivering cold products / meats.

curious as to why you would suggest an arduino for each sensor? if he's going to need to wire everything anyways; wouldn't it be easier and cheaper to just deal with one board with a bunch of digital temp sensors instead of multiple boards and serial communication between all of them?