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

[tr6scott]

We have been using the Banner DS18VN6LP photoeyes for a few years now, and absolutely love them, the packaging, the polarized light, the multiple mounting options.

http://www.bannerengineering.com/en-...f/17406#wiring

The DSC and roboRio have pull up resistors, so when nothing is wired, all inputs read TRUE, high value. When you want to get a signal, you need to short the signal pin of the PWM to ground.

On the DSC, these sensors worked find when powered from the 12v PDP, and were NPN so would short the signal to the negative of the battery.

Yesterday we stripped two bots of controls and were testing the sensors pulled off to put back into stock for this year on the roboRio.

We were powering them from the VRM 12V 2A connectors, and all of these Banner sensors tested bad, they would not read changing states on the roboRIO.

We also had some Allen-Bradely units similar to the logomotion line following sensors, but in a different tubular packaging that worked fine.

I fine it really odd that all of the banner sensors tested bad, so I do not have faith in the test.

So now I am thinking maybe the VRM has some circuitry that may isolated the ground being shorted by the sensor?

I did not think to test sensors when powered from a PDP channel.

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?

[Jared]

I'll bet that the 12 volt supply on the VRM is isolated for some reason.

We've always powered our yellow banner sensors straight from the PDB with no regulator, and we've never had any issues. You may want to try this.

[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.