Ultrasonic Sensor Reading

JeffPLC · Feb 19, 2015

Hello everyone,

I have a pretty basic question which I can't seem to find any information for. I have an ultrasonic sensor connected to my analog input (IF16) which is hooked up to a 1756-L61 controller. I can't seem to find out where exactly to read the incoming data. I have all of the following steps figured out afterwards I believe but I just can't seem to find how to view the initial values.
I'm fairly new to PLCs and I'm sorry if this is a very basic question, but I'm having trouble even locating documents online to outline this process.
Could someone help me out? Or even point me in the right direction?

Thank you

sparkie · Feb 19, 2015

What type of PLC you are using is pretty important.

I know with Allen Bradley PLCs you can view the data table for the location of your sensor input (such as I:3/4) and that value will give you a binary word for the sensor input.

I don't know if this is for a level or not, but you would do something like, verify the container is empty, or at what you consider base level, then check the word for that input address, then set that as your max with SCP instruction.

Then get the value for a full container and set that as your max in the SCP instruction.

dginbuffalo · Feb 19, 2015

Look in the controller organizer and find out which module # your IF-16 card is. Once you know go into controller tags and and find the address and tunnel down into it. It's going to look something like this: Local:2:I.Ch0Data

JeffPLC · Feb 19, 2015

It's Rockwell Software.
I'm looking at the channels but there's still no relevant information. All I see changing is the rolling timestamp.
Also, curiously, the module doesn't show channels 8-15 but shows 0-7 no problem. Is there something obvious I'm missing? The module is corrct and even says there is a match.

Bering C Sparky · Feb 19, 2015

I believe that you can change the way the values are displayed from binary to decimal.
Click where it says binary next to the channel you want and change to decimal.

Also look again for channels 8-15 if they are not lumped in with the first 8 continue looking down or maybe even look to the next set that can be expanded on the tree.

dginbuffalo · Feb 19, 2015

JeffPLC said:
It's Rockwell Software.
I'm looking at the channels but there's still no relevant information. All I see changing is the rolling timestamp.
Also, curiously, the module doesn't show channels 8-15 but shows 0-7 no problem. Is there something obvious I'm missing? The module is corrct and even says there is a match.

It is because the module was originally set up as "differential" inputs vs. "single ended". it can do 8 differential or 16 single ended.

Have you configured the channel when you double click on the module itself? It must be set up for type and range.

JeffPLC · Feb 19, 2015

Well we've tried rewiring it to channel 0 to bypass any issues but now the reading is still stuck at 0 regardless. Every few seconds it switches to something like 3.4165e-4 which is close enough to call 0. The sensor seems to be working as the LEDs indicate so. I'm not quite sure how to configure the channel like you say but I hoped we'd at least get a reading to go off of first

dginbuffalo · Feb 19, 2015

You should be able to click on your module and go to the configuration tab as shown in the picture. Is this a loop powered device? Are you sure it's wired correctly? If it is not loop powered, the LED's could be on and still not wired correctly. Double check the manual and make sure you have wired properly for single ended of differential input.

PS- Can't get my picture to load but i will try again.

JeffPLC · Feb 19, 2015

It's a strange configuration but I believe it's hooked up correctly as once I hit a switch on the sensor, the data went from 0 to 1.1945 or so. I still can't get it to change but that means there's at least SOME connection in some way

dginbuffalo · Feb 19, 2015

OK- well since it doesn't work, I'd have to think something isn't right. I was able to attach the picture of the communication tab.

Can you provide even a penciled drawing of how you have it wired in?And also the a few pics of the module setup? Are your sure the sensor is on the right wires for mA or voltage or whatever your using? does the sensor require setup?

Also-I believe on one of the other tabs in the picture there may be a radio button that you have t toggle on to enable the channel your on. Not quite sure because I'm used to the 1769 Compact I/O modules.

JeffPLC · Feb 19, 2015

Yeah I've already configured it for mAmps, changed it to 4-20, and the switches on the sensor itself shows mAmp output. We've wired it according to the mAmp input for the PLC. Here's a pic of how it's wired.
It receives it's 24v signal from an external supply so we just have the signal and ground going into the PLC with the jumper wire connecting it so it's on channel 0.
Any ideas?

dginbuffalo · Feb 19, 2015

Wiring looks ok according to manual. Have you tried swapping the black and white wires for the hell of it?
Does the module status say "running"?
Have you had any other inputs on this card that were working?
Do you have a milliamp simulator?
what brand ultrasonic and model?

DLite · Feb 19, 2015

Your wiring is incorrect. You have it wired for a differential input..

you should be on terminals 1 (+) and 2, and a jumper between 1 and 9.

dginbuffalo · Feb 19, 2015

His module is configured for differential inputs so I was assuming that's what he needed. If there are other differential inputs they cannot be mixed and matched as far as I know.

JeffPLC · Feb 20, 2015

Looks like it's working now

After playing around with the configuration for a bit and resetting it, this morning I seem to get a different reading. Thanks for all your help! I appreciate it!
Now I'm just going to set the windows and make sure it operates with a display.

Ultrasonic Sensor Reading

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