We are a 2nd year team and are trying to improve our programming by learning how to use sensors, etc. We would like to try to use the maxbotix sensor that was included in the KOP last year, but we aren’t sure where to start. Did anyone use it last year? If so, how was it wired? How was it connected to the Rio?
We also have a General purpose Rockwell ultrasonic sensor model 873M that we would like to use, but again, we are unsure of the wiring and connections to the Rio.
What other sensors (other than ultrasonic) would you recommend that we learn? Any help would be appreciated.
For basic operation on either sensor, if you power the sensor it will continually output an analog voltage proportional to the distance to the target. You can then read that using an AI (analog in) ports on the roboRIO.
I don’t see a pin out diagram for the Allen-Bradley sensor (on mobile), but Ive used the Maxbotix ones before and they’re very simple to set up. Wire +5V from the AI port to + on the sensor, GND to GND, and AN on the sensor to signal on the roboRIO port. Then reference the sensor as an analog input.
If you want to get your robot to specific location(s) during autonomous, encoders on the wheels and/or one of the navigation IMUs would be appropriate; we just purchased some Pigeon IMUs this week so we can figure them out.
If you’re interested in knowing the location, orientation and other states of your manipulators, encoders (including absolute encoders) and various potentiometers and limit switches would do you well.
If you’re interested in locating game pieces and field elements, range finders (e.g. the ultrasonic) and cameras/vision processing and possibly limit switches are indicated. On range finders, note that if you are interested in short ranges (less than a couple of feet), you can usually find an infrared sensor that will do the job for a lot less than ultrasonic. We’ve always had good performance from Sharp IR sensors at a great price, whether binary (present/absent) or analog (output voltage is a function of range to target).
There are a number of web sites with sensors, including McMaster, DigiKey, Mouser, SparkFun and AdaFruit, but I find that when I know what I want to do but don’t know the best way to do it, browsing for sensors on RobotShop.com provides inspiration.
We did get the sensor through first choice, but I am having trouble following your other post. Our wires are white, black, brown, blue. The white wire is the teach wire, the brown is the 10v, the black is the analog output, and blue is 0v DC (so I assume ground).
How did you wire the 5k resistors? Did you use them to connect 2 wires from the sensor together?
Brown goes to 12V 500ma on the VRM
White needs to be accessible for programming (I attached it to a shielded spade terminal so it won’t short on anything but is still accessible)
Black goes to one end of the first resistor
Blue goes to ground on the VRM, ground on the signal cable to the roboRIO, and one end of the second resistor.
The white (signal) wire in the cable going to the roboRIO is connected to the other side of both resistors.
You might want to or be able to omit some of the ground connections, but I connected all of them for the best signal quality (correct me if I’m wrong).
The manual explains it in detail, but you use it to set the sensing range. You put an object where you want the sensor to output 0V or where you want it to output 10V, then connect the programming wire to 12V or 0V.
It really doesn’t matter at all. The sensor can output up to 200mA. You just need enough load to overcome noise issues. Really anything between like 25Ω and 100kΩ would work, as long as both resistors are the same. I’d say do between 5k and 1k to get at least 1mA flowing out from the sensor.
I looked through the robot rules for last season, but didn’t see anything regarding sensors. Are any sensors OK to use? Are there specific potentiometers that have to be used or is any potentiometer ok?
Sensors and their connections are considered custom circuits and must follow the rules accordingly. They also need to follow the price rules, and any other rules that apply to all robot parts. Other than that, there are no limits or restrictions on what sensors you can and cannot use.
