Help with Vision230 and a new Digital Sensor

[gal]

Greetings,

I'm new to the forum and to Unitronics PLCs in general but wonder if you could help me:

I'm setting up a small controlled environment chamber for biological experiments - we are a bit "budget challenged" so had to go a bit DIY as much as we can (hence the "newbie" questions here ).

In order to control the setup we've sourced a new Vision230 with V200-18-E3XB and V200-19-ET1 modules.

We've got a sample of a "digital" Humidity/Temperature sensor from sensirion we'd like to use but don't know how to connect and configure the PLC to communicate with it.

The sensor is SHT11 - Digital Humidity Sensor (RH&T) which has a Serial Data interface described in it's Specification Sheet.

There are few Sample Code at their site - in the Download Center.

Is it even possible to directly connect the Vision230 and that sensor w/o additional interface? How (where do I connect it) ?

If it is - how do I setup/program the controller to get appropriate readings?

I do understand this might be a bit above a "beginner" level but I'm a fast learner and promise to do my "homework" if someone at least direct me to the right direction.

Regards (and happy Xmass) ,

Gal

[Joe Tauser]

Here's the datasheet on the sensor:

SHT11

The V230 allows you to access the serial ports from the program, but it's RS232. You'll have to convert this to the 5V TTL level the sensor is looking for. You can buy an assembled converter or integrate an IC into your circuit using something like the MAX232 chip. Here's one I found:

RS232 converter

As for the programming side, read all the Help and study the examples on the Protocol function block. You may be better off looking at a humidity sensor that has an analog output, since you already have an EX3B expansion module-

Humidity Transmitter

Good luck!

Joe T.

[gal]

Thank you so much Joe,

After more reading It does seem a bit over my head at the moment

However, I found out that the same source offer similar sensor modules based on PWM or SDM communication (can be converted to analog output with a simple LowPass filter):

SHT21S_SDM

SHT21P_PWM

These might be better and require less efforts from me to implement.

Which one you'd expect to be easier to set up?

Can the V230's HiSpeed input handle 120Hz PWM signal at say 10bit resolution?

Or better to convert to analog and saves the headache !?

Regards,

Gal

[nagaraj]

You are far better off using sensors with Analog Output. I just completed building a device using Temperature/RH transmitter using 4-20 mA analog output. Dwyer Instruments has a good catalog to choose from.

[Joe Tauser]

It looks like you can convert the PWM to 0-5V, which you can read with the -E3XB module. I looked through the data sheet, but they didn't give R and C values for your filter - you may be able to contact the manufacturer and have them send you a circuit. Time to start wiring stuff up and see what works.

Joe T.

[gal]

Thank you guys - very helpful indeed

It looks like you can convert the PWM to 0-5V, which you can read with the -E3XB module. I looked through the data sheet, but they didn't give R and C values for your filter - you may be able to contact the manufacturer and have them send you a circuit. Time to start wiring stuff up and see what works.

Joe T.

That does seem the preferred direction and the manufacturer is responsive as well.

I wonder if I can easily utilize the PWM signal directly before modifying the sensor for analog.

I'll try to update you after some experimentations...

Please feel free to share any tips or useful insights on that matter .

Regards,

Gal

[Joe Tauser]

You don't have to modify the sensor- the RC circuit gets connected directly to the PWM output. Here's an example:

PWM circuit

Just Google "convert PWM to analog voltage" and you'll find all kinds of good stuff.

Joe T.