Photoeye's not working-Difference between RoboRIO and Digital Side Card?

[ozrien]

The VRM is not isolated. If you measure the voltage difference between the VRM ground and the Rio ground you should find it to be very close to zero .

Measure the light sensors input voltage to confirm its powered properly. Then measure the signal voltage to see why the readings from the Rio don't match your expectations. That might reveal what's going on.

[Lightfoot26]

You are not alone! We were testing our banners on the new control system and experienced the exact same thing! The similar Allen-Bradley sensors that came in the KOP in 2012 worked fine! I did find (and this is a weird observation that may or may not have anything to do with the problem) when I probed for continuity across the signal line at the roboRIO while it was plugged in, and the negative terminal the sensor was plugged into at the PDP, the sensor began functioning properly both on the meter and in code. Weird I know, but it was something I noticed.

[tr6scott]

Omar,

Is the power supply leg to the roboRio isolated ground?
Seeing there is another team having issues with Banner sensors, I am going to and wire the sensor power from the same source as the roboRio power and test on Tuesday.

I could also drop one of these sensors off to you for testing Monday on my way home from work.

Scott.

[Al Skierkiewicz]

Originally Posted by Lightfoot26

I did find when I probed for continuity across the signal line at the roboRIO while it was plugged in, and the negative terminal the sensor was plugged into at the PDP, the sensor began functioning properly both on the meter and in code. Weird I know, but it was something I noticed.

Seth,
Can you tell us which meter you were using and I am guessing you were in continuity mode and not resistance mode? It is possible that there is a component in series with the negative lead on one or more of the control components. Your meter might have reduced the impedance sufficiently to allow the sensor to turn on. Depending on the component and the series impedance, it is possible that the sensors are not receiving sufficient power supply to operate. As I remember, the Banner sensors require a specific power supply voltage.

[Alan Anderson]

We plan to use Banner sensors this year. I had expected to use the VRM's 12 volt supply to power them. Testing them on our robot-in-progress is now high on my to-do list for our next work session on Tuesday.

[Lightfoot26]

Originally Posted by Al Skierkiewicz

Seth,
Can you tell us which meter you were using and I am guessing you were in continuity mode and not resistance mode? It is possible that there is a component in series with the negative lead on one or more of the control components. Your meter might have reduced the impedance sufficiently to allow the sensor to turn on. Depending on the component and the series impedance, it is possible that the sensors are not receiving sufficient power supply to operate. As I remember, the Banner sensors require a specific power supply voltage.

Al, I guessed that some circuitry internal to the meter was affecting my results but I couldn't quite put my finger on it. I was in continuity mode and I believe it was on one of our Extech MN35's (I am away from the shop and can't confirm this, but I am fairly confident that's the meter we used). It was very odd, but the sensor functioned perfectly with the meter in place and operated as Scott described in the original post when the meter wasn't being used. If it helps, the working Allen-Bradley sensors are the 42EF-D1MNAK-A2 and the Banners we tested were the QS30LV.

[Al Skierkiewicz]

Seth,
That meter, as most modern meters, apply a current to the probes when in the "diode" mode and then measure the voltage drop directly. In a normal diode or transistor junction, the meter would read 0.7v. The specs say that the current in this meter is limited to 1 ma when in the diode mode.
I have to ask, was the "ON" indicator on the sensor illuminated and the output was not sensed by the roboRio? The RoboRio has a 40k pullup resistor to 3.3 volts which may not be enough to pas current through the Banner sensor.

[tr6scott]

Did some more extensive testing tonight during our meeting.

The Working AB Part number was
42CA-P2MNB-A2

Another non-functioning Banner sensor was QS30LV

We also found the following Banner Switches to also work.
T18SN6FF50

T30SN6FF400

I tested with the sensors connected to the both the 12v 2a power rail, and also wired direct to the same power leads as the roboRIO without any impact on working state.

Both non-working Banner part numbers status lights work as expected, and I tested multiple sensors of each type, Power indicator works, and sensor tripped worked, just would not fire the roborio input.

[crake]

Questions:

- What are the properties of the Banner sensor? What clues does the sensor datasheet give you?
- What is the pull up/down configuration of the roboRIO for that particular DIO line? Hint, pg 15 of the user manual - or look above
- What does this circuit look like when "on"? "off"?
- Will this work?
- If not, how can you change the circuit to make this work?

Extra bonus

- Why did hooking up a multimeter make this work?

[tr6scott]

I guess it is no longer accepted to ask "Any hardware guys can explain what is going on, or what power source I should be used to power the sensors so the RoboRIO can sense the ground state?"

If you are not going to explain what is happening, could you at least give some links on where I could go to find the answer?

I'm just trying to figure out if I have spend another $600 on sensors that work with the roboRIO, so we have a functioning bot is the near future.

From your post, you obviously believe there is some way to make these sensors work with the roborio, yet I am no closer to finding that answer.

[tr6scott]

Looks like the roborio has 40kOhms to 3.3v pull ups, while the DSC has 10kOhms to 5v pull up.

[tr6scott]

Sensor Cut Sheets, DS18 non-working, T18 working.

[FrankJ]

We have not got this far yet so I really have not tested anything. But. The RoboRIO is actually 3.3V (5V compatable) (If I understand what the NI guys said.)& the side car was 5V? Assuming you are not seeing the 0V state, maybe the Banner is not pulling the pin low enough?

Looking at the RoboRIO specification Low state is 0.0 V to 0.8 V. On state for the DS18 is <1.8 volts. So it working looks iffy. On state for the T18 is <1V The RoboRIO spec is on the NI web site.

Although looking at the NI 9403 (CRio DIO module) it has the same 0.8V max for V low Maybe it is more forgiving?

[Alan Anderson]

Originally Posted by tr6scott

Sensor Cut Sheets, DS18 non-working, T18 working.

The suspicious difference I see is the "ON-state saturation voltage".
DS18: < 1.6V @ 100 mA
T18: < 1V at 10 mA dc, < 1.5V at 100 mA dc

Perhaps the roboRIO input's logic 0 threshhold is too low for the DS18 to satisfy without assistance. When I get to the workshop on Wednesday I plan to do some experimentation.

[tr6scott]

Thanks Guys, the delivery on the AB ones are 2/16 from the factory...