potomac
1
I have some questions regarding RS232 sensors, which I have laid out in structured form below. If you could educate a total beginner, that would be greatly appreciated
1). To communicate the Arduino, I know that I'll need a RS232-to-TTL converter module. I found two below that seem to have good reviews. Are there any better options around? I would like to keep it as small as possible, with the one caveat that it have 2-4 holes on the corners so I can mount it with screws and metal standoffs.
The modules I found:
1). "RS232 Serial Port to TTL Converter Communication Module for Arduino - DX.com"
2). "RS232 Serial Port To TTL Converter Module for Arduino #04902615 - MiniintheBox.com"
2). Those two modules I listed above have different numbers of pinouts, and different abbreviations for pinouts. Excluding VCC and GND, one has 2 additional pinouts and one of them has 4. See picture attachment called "Pinouts" below. Is there a set of pinouts you'd want in general?
3). For reference, the datasheet for the oxygen sensors I want to attach to my Arduino Pro Mini is here. Does this inform which pins I need on a converter module? I don't see any data relevant to answering this question.
http://www.presens.de/fileadmin/user_upload/products/Transmitters/EOM-O2-mini/160615_TR-EOM-O2-mini-16-01_w.pdf
4). I know that the Pro Mini has one UART. Could I attach 3 of the oxygen sensors above with SoftwareSerial? How reliable has it gotten over the years? I've read that previous versions were dicey in terms of data quality. And also that are limitations to data speed.
I found this resource but it hasn't been updated in awhile: SoftwareSerial Library, DO NOT USE. NewSoftSerial works much better.
Does this inform which pins I need on a converter module?
It says RS232 and the pin out for that is standard. However that is not a data sheet is is simply a sales brochure. You need the data sheet to see how to talk to the sensor and what exactly the sensor sends back to you.
Could I attach 3 of the oxygen sensors above with SoftwareSerial?
You could but you can only look for one serial signal at a time. This is no problem if you have to send a request for data to the sensor and it then answers you. But if it sends data all the time you will miss some readings. Again you need a data sheet for the sensor.
Are there any better options around?
Well if it were me I would just make one using one of the many converter chips like a MAX232. It looks like you don't need that 9 Pin DIN connector and you would be better off using just wires for the connections.
potomac
3
Thanks Mike
I will contact them for a real data sheet
Understood that with Software Serial the Arduino can't receive all the data at once.
How far apart would the different sensor data points be staggered? Are the speeds comparable to IC2? 4800 baud rate?
Grumpy_Mike:
It says RS232 and the pin out for that is standard. However that is not a data sheet is is simply a sales brochure. You need the data sheet to see how to talk to the sensor and what exactly the sensor sends back to you.
You could but you can only look for one serial signal at a time. This is no problem if you have to send a request for data to the sensor and it then answers you. But if it sends data all the time you will miss some readings. Again you need a data sheet for the sensor.
Out of interest, do you have any idea of the price of those oxygen sensors, cannot see any mention of their price, by quote only, so it suggests they are very expensive ...?
Also no details of their data protocol /datasheet which suggest they are not a typical consumer supplier.
Wonder what you are trying to measure and if there is a simpler solution to you project ..?
Are the speeds comparable to IC2?
It depends on the baud rate. I2C operates at about 10K bytes per second, that is the equivalent to 100K baud.
How far apart would the different sensor data points be staggered?
It depends on if you command them to read or they spew out the readings continuously. However, I would have thought that the reaction rate of the sensor is going to be in the order of seconds not milliseconds which is the likely stagger time between different sensors.
ricky101:
by quote only, so it suggests they are very expensive ...?
I agree, I would be very surprised if they are less than $300 a pop.
potomac
6
To ricky and mike: yep, they cost some serious coin. Several hundred dollars. I'm not aware of any cheaper options that operate in a similar manner. They are finely tuned sensors that look at the concentration of O2 in liquids with fiber optic sensors that never touch the liquid. I'm sure there are commodity O2 sensors on Digikey but they will have to come in contact with the liquid.
It depends on if you command them to read or they spew out the readings continuously. However, I would have thought that the reaction rate of the sensor is going to be in the order of seconds not milliseconds which is the likely stagger time between different sensors.
To Mike: The data gathering timeline might look something like this. Possible with software serial? Every thirty seconds, trigger a barrage of 3 very quick staggered readings?
