I'm trying to develop a on/off controller. The idea is to keep the temperature in element B equal to the temperature in element A, so I would need to connect two sensors and a heater. I would also need to record the temperature in each element. The algorithm would be as simple as:
if tempA-tempB>0:
on;
else:
off;
The distance between the sensor and the controller can be up to 50 feet and the heater would have a power of around 2000W.
What type of sensors should I use? How can I turn on a off a heater with that power using Arduino?
I would use a relay to control the heater and perhaps a mosfet to control the relay. I myself have always like ds1820 temp sensors but they may not be suitable for your application.
What exactly are you measuring? Gas or water? Did you consider the everything except how to turn the heater on and the sensors such as power supply?
what is your temperature range ? if your kiln is running at 1,000 deg C ?
most of the sensors we use will melt, you would need to use a thermocouple.
if you want to keep the ice makers about the same temp, a thermocouple would not offer any resolution and many sensors would not respond at all.
the majority of temperature sensors would short out if you submerged them in the two fish tanks.......
what sort of DC power source are you using for your heater ? batteries ?
is it a 5 volt heater ? or maybe a 3-phase 480 volt device ?
what is the worst case if there is a faulure of either full on or full off ?
you would have to provide a separate safety device to prevent such a failure.
as for the ARDUINO end.
a NANO at each end with the appropriate sensors and a simple 4 wire cable with a RS485 module on each end and you can have reliable communication.
how are you controlling the blast furnace now ? or is it a coffee maker ? soda cooler ? chances are that whatever you are currently using, there is a way to control that device.
if you can tolerate loss of signal, use wireless
if you cannot tolerate any loss of signal, use wire.
the 50 foot distance presents a problem with sensor wires going to one device.
that is why I would start with two and have them talk.
the controller (Arduino with relay) should be near the controlled device.
the remote unit would be the sensor only device.
I came to Australia from Chile on a Working Holiday Visa and got my first engineering internship at a Pre-Cast Concrete company. I need to impress my boss to get sponsored and stay in this great country, so I would really appreciate your help.
I'm trying to build a device that reads temperatures from A and B and activates a heater if B is lower than A. As of now these are the components I would be using:
Would it work fine if one of the thermocouples is wired through a 15m long cable? (to my understanging the MAX6675 takes care of the noise generated at such length)
Where can I find how to connect each device to the Arduino board?
Study up on thermocouples. unless you measure the voltage generated by splicing in copper wire to extend the distance and take that into account when calculating the temperature, you will have problems. Try to get thermocouples with shielded wire for the entire length you need.
Yes, all that is possible.
Start simple - the thermocouples will need a buffer to get their levels up a meaningful level for the Arduino ADC to convert them, or better yet the buffer will contain the analog buffering and the ADC in one chip.
LCD screen, SD card, relay, are all pretty standard stuff.
Which thermocouple are you using?
To extend a thermocouple, you need to use thermocouple extension wire. This is made of the same dissimilar metals as the thermocouple itself.
I found that the MAX6675 suffered badly from radio interference in one application. To the point of getting negative kelvin temperatures. It was not possible to just ignore the low values because I was trying to measure something which is very cold. Eventually I replaced it with MAX31865 and platinum RTD sensors using a 4-wire configuration.
But concrete cures around room temperature. You don't need thermocouples for that. The only reason for using old-style thermocouples or RTD's is if your temperature range exceeds that available on a nice modern sensor like the DS18B20. They are so much easier to use. There's no worry about using the right kind of wire and any interference is detectable by examining the checksum in the digital communication. They are also cheap, if you need disposable sensors that will be buried in concrete forever.
For the heater, how big is it? The basic little relay modules that you get off ebay are great for switching a 12v lamp or motor. They aren't safe to use on mains power.
If you haven't discovered Core Electronics yet, I've bought things from them in the past and I was very happy with the range of products they have which suit this kind of Arduino project.
The other thing I'd like to know about this is: Where is this thing used? If it has to go out to building sites and get thrown in the back of a ute, then it needs some serious consideration on the box and vibration-proofing all connections inside the box.
MorganS:
To extend a thermocouple, you need to use thermocouple extension wire. This is made of the same dissimilar metals as the thermocouple itself.
I found that the MAX6675 suffered badly from radio interference in one application. To the point of getting negative kelvin temperatures. It was not possible to just ignore the low values because I was trying to measure something which is very cold. Eventually I replaced it with MAX31865 and platinum RTD sensors using a 4-wire configuration.
But concrete cures around room temperature. You don't need thermocouples for that. The only reason for using old-style thermocouples or RTD's is if your temperature range exceeds that available on a nice modern sensor like the DS18B20. They are so much easier to use. There's no worry about using the right kind of wire and any interference is detectable by examining the checksum in the digital communication. They are also cheap, if you need disposable sensors that will be buried in concrete forever.
For the heater, how big is it? The basic little relay modules that you get off ebay are great for switching a 12v lamp or motor. They aren't safe to use on mains power.
If you haven't discovered Core Electronics yet, I've bought things from them in the past and I was very happy with the range of products they have which suit this kind of Arduino project.
The other thing I'd like to know about this is: Where is this thing used? If it has to go out to building sites and get thrown in the back of a ute, then it needs some serious consideration on the box and vibration-proofing all connections inside the box.
JayMan:
I would use a relay to control the heater and perhaps a mosfet to control the relay. I myself have always like ds1820 temp sensors but they may not be suitable for your application.
What exactly are you measuring? Gas or water? Did you consider the everything except how to turn the heater on and the sensors such as power supply?
I'm measuring temperature in Steam Cured Concrete elements and in a heated cylinder sample of the same concrete.
I know a have to do some coding but I reckon it won't be too difficult for me. I'm considering the following components:
1500W is not large, but it's 240V, which must be treated with care.
Can you get a professional electrician to do the 240V wiring for you? Maybe there's an electrical engineer on staff too?
Look into how other Arduino enthusiasts have modified hot plates and toaster ovens for reflow soldering. The same safety principles they use can be applied to your project.
Room temperature to 70C definitely sounds like you should be using a digital sensor and not a thermocouple.
MorganS:
Look into how other Arduino enthusiasts have modified hot plates and toaster ovens for reflow soldering. The same safety principles they use can be applied to your project.
Actually I should have said...
Most of these kinds of projects posted online are really terribly unsafe. Once you've seen enough of them to identify which ones are unsafe, then you have enough knowledge to start designing your own.
Considder putting each thermocouple in a box for local measuring
connect them with an RS485 cable.
if you have aboard with a bunch of wires, it looks like a hobby board.
if you have a pair of enclosures that are connected with a wire, it looks more professional.
thermocouples measure the joint where the two dissimilar metals meet. that can be at the end where your copper and constine (T-type) junction is, or when you connect copper wire and create a new thermocouple junction.
to make a thermocouple, take two wires, one copper, one constine and twist them together. presto ! instant thermocouple.
The wire of up to 30ft long would be the beam-arduino thermocouple. The sample-arduino thermocouple and the arduino-heater wire would be about 6ft long.
Why would the wire length become a problem for my device? I haven't yet understood what should I use instead. Also, I don't care if the signal is +-1 degC off the true value.
Hi,
These devices;
and
Are built for industrial environments, with EM fields and power supply noise immunity.
The Arduino controllers and their modules and shields are not designed for this sort of use.
The modular construction of the Arduino system does not allow easy earth and power supply routing that is required to minimise industrial noise.
Wire length is a problem because the voltage produced by the thermocouple is in the microvolt range. Even small amounts of interference from nearby motors or transmitters can easily exceed this level. The longer the wire is, the more 'things' it gets near and the more efficient it is at picking up that noise.
