Is the roboRIO DIO Compatable with the AB Line Sensor?

[oscarfonseca · Accepted solution]

@MarkBalla,

After checking with our R&D team, I can confirm you that the maximum allowable input voltage is 5.25V. Anything higher could potentially cause damage to the roboRIO.

Maximum Allowed Voltage in the roboRIO's DIO

Thanks,

[MakShiftRobotics]

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@mjshafer93 wrote:

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The power and ground of the sensor would go to the VRM I assume as it can output 12 V. Would the data out (Either dark or light) pass through the Sparkfun board and then into the DIO of the Rio?

How would the digital out be connected to the logic level converter? Is it as simple as connecting the sensor out to the 'HV' pin and then connect the 'LV' pin to the rio?

Thanks

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Hi,

You can get the 12V from either the VRM or the PDP, I would probably do the VRM since it will be going though a 10K resistor (so pulling less than 1 mA) and you want this to be along with the last things to fail in the case of brown out (as opposed to hooking it to the PDP where it will be among the first).

Yes, the signal from the sensor would "pass" through the level converter. Hook the sensor up to an HV and the desired signal pin on the DIO port of the roboRIO to the corresponding LV pin. (you can get the 5V and ground for that side from the DIO pins or the VRM).

I'm attaching a diagram in case I'm not explaining very well.

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Hi,

Thanks so much for getting back to me! I understand how to wire up the sensor now and I appreciate it! If we plan to use 3 line sensors on our robot could we in theory just use one of these boards because it has 4 channels?

To get the sensor working properly with the Rio do we need any other resistors or custom circuitry? I have seen some teams applying resistors of different values linked to each other before connecting it to the DIO Rio pin. I assumed it was as simple as connecting the LV channel of the board to the input pin of the DIO port. I figured it would be similar to setting up something such as a limit switch where the Rio is looking for just on or off from the sensor port.

Using the 5v output and ground pins of the DIO port to power the board is a great idea, thanks!

[mjshafer93]

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@MakShiftRobotics wrote:

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Hi,

Thanks so much for getting back to me! I understand how to wire up the sensor now and I appreciate it! If we plan to use 3 line sensors on our robot could we in theory just use one of these boards because it has 4 channels?

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Yep - exactly why this is great for such an application.

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@MakShiftRobotics wrote:

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To get the sensor working properly with the Rio do we need any other resistors or custom circuitry? I have seen some teams applying resistors of different values linked to each other before connecting it to the DIO Rio pin. I assumed it was as simple as connecting the LV channel of the board to the input pin of the DIO port. I figured it would be similar to setting up something such as a limit switch where the Rio is looking for just on or off from the sensor port.

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There are a couple of reasons to consider adding resistors when using custom circuits.

One is if the current drawn will be too high for the DIO pin/port (for example, if I were to take the the DIO signal to an LED to ground, that would basically be a short, adding a 330 Ω resistor knocks the current down to 5/330 or roughly 15mA). For using the stepper circuit, you can see how much current will get pulled from your pin if you go to that demo (MultiSim Live link) and look at the current on the probe (where the DIO pin connects in - on the left). As long as it is reasonably low (techinically, lower than the spec for max current pull, which is 15mA if I'm reading the spec sheet correctly), then you won't need a resistor for this.

What the teams that discussed this on CD are landing on is using to resistors in series as a voltage divider (https://learn.sparkfun.com/tutorials/voltage-dividers/all). This a way of using the voltage drop across two resistor to only grab a 5v signal out of the 12v signal.

Yes, the RIO in this case is looking for an on/off case (so reading it as a DI should work perfectly well).