View Full Version : Connecting Telaire 8001CO2 sensor to BS2 quesions... Anyone good with RS-232??

Brann Fenix
08-31-2006, 11:13 PM

I am working on a little side project for a friend of mine which requires a Telaire 8001 CO2 sensor. I have only really worked with a TTL LCD as far as interfacing via serial communication with the BS2, so this is new stuff for me. I just wanted to ask for some ideas and run some stuff by everyone before I ever power this sensor up and risk damage. Here is what I know:

a. The sensor using RS-232 and has an optional cable and PC software. This means I will need something on the lines of a MAX232 in order to connect to it.
b. The pin out for the sensor is as follows:

Pin 1 = Not Used
Pin 2 = Not Used
Pin 3 = Relay Normally Open
Pin 4 = Relay Common
Pin 5 = Relay Normally Closed
Pin 6 = 4-20mA Output
Pin 7 = Signal Ground
Pin 8 = 0-10v Output

c. The docs for the sensor are here http://www.gesensing.com/downloads/manuals/8000singlemanual.pdf

e. The sensor has an optional cable and software from Telaire for connecting to a PC the docs for that are here http://www.edinst.com/pdf/telaire/uip8000manual.pdf

f. I read in an old forum post about someone having a CO2 sensor that "put out a 0-10VDC signal that represents a 0-2000
ppm reading" and I noticed this device has a 0-10v Output... Could this sensor work like that?

Now, I am trying to avoid paying out $54+ for a 200kbyte Visual Basic app and what I think is a simple 2 wire to DB9 Cable made only for connecting to a PC which in the end I do not even need. I understand without paying for their cable and software I do not have much hope of figuring out how to configure the device via the RS232, since I assume they have command codes sort of like the LCD I used. I do not mind much since the default config at the factory will work for what is required. The first stage of my plan includes trying to connect the sensor via a homemade cable to my computer and reading the outputs via hyperterminal or something of the like. I would think that since they have PC software to read the outputs it must output something readable via the serial port which will give me a starting point for connecting it to the BS2.

With all that said I am off to do some heavy reading. If someone has worked with these sensors before any info would be a great help and if it comes down to it I guess I will just have to buy the software/cable kit and work off the info that gives me...


Power question:

The sensor requires 18-36V rms OR 18-42VDC 100mA Peak, 70mA avg @ 24VDC

Am I correctly thinking that this 13.5-30VDC/1000mA AC-to-DC Adapter from radioshack Model: 273-1668 | Catalog #: 273-1668 will do the job?

I am 99.9% the ratings on the AC to DC adapter mean the most it can output is 1000mA @ 30VDC which would mean the sensor at 30VDC would draw 80ish mA ? *ball park guess I did not do the math this second* If that thinking is correct it should work fine right?

Thanks in advance,

Post Edited (Brann Fenix) : 8/31/2006 4:25:34 PM GMT

Chris Savage
09-01-2006, 03:02 AM

·· The pinout (8 pins) of your sensor·are typical of that kind of sensor, but don't appear to have anything to do with RS-232 Serial communication.· The clues are in the second document, which seems to indicate there is an RJ-11 or similar jack that this special cable plugs into (I didn't see it in the other manual).· Anyway, you may need to use something like our BSLA (BASIC Stamp Logic Analyzer) to decode the data being sent.· You will need a driver such as the MAX232 if using standard I/O pins.· The BSLA would allow you to see what data is being sent back and forth and actually show the characters and ASCII values.· You can find more information about that feature in the AppNotes on the following page.


· As for the power supply, the one listed below should work just fine.· I hope this helps.· Take care.


Chris Savage
Parallax Tech Support
csavage@parallax.com (mailto:csavage@parallax.com)

Tony B
09-02-2006, 09:29 AM
I have installed approx 800 of these devices over the last 2 years. Getting data from this device is easy.

The reality of this device is that it simply reads the CO2, It doesn't need to "talk" to anything, it can simply provide an analog ( 0 - 10 vdc or 4-20 madc) output. As a bonus, it can also close a couple of relay contacts depending on the settings of the sensor.

Enough of that, simply put a 250 ohm resistor between the 4-20 mADC (pin 6) and signal ground pin (pin 7), and you have just made a linear 2 - 5 vdc signal to span 0 - 2000 ppm.

I have been powering my sensors with a 40va 24vac transformer -- grounded secondary. The 40va is overkill for the sensor alone, but I am also powering a bunch of other automation equipment too. All is working swell.

Every problem has a solution. Some don't even create more problems.