Wille the LV-MaxSonar-EZ1 range finder interfere with other sonar range finders?

[Pickle3756]

I was wondering if the sonar range finder provided in this years KoP will return incorrect data if other range finders are in use on the field

[Sparks333]

In short, yes - it will also return poor values if used too close to the floor, or in a complex environment, such as a corner, when used at particular angles. The longer answer is that the LV-1 has a fairly narrow beam, and can be set to fire relatively infrequently, so if you average your results and throw out outliers, it can still be useful, since the sources of interference will be coming and going. If you use multiple rangers on one robot, however, look into chaining them so they fire sequentially - otherwise you do run the risk of interference. Hope this is useful information.

Sparks

[Al Skierkiewicz]

It is possible but there are ways around it. Several matched readings for instance. It is unlikely that teams will or should enable a range finder for an entire match. They should enable just when needed.

[Sparks333]

I hate to disagree with you Al, but the simplest use of the sensors is to hook it to power and read the analog output - I think this is likely how most teams will use them. In this case, the sensors will come up and begin running in free-ranging mode, firing off several times a second with no inputs required from the robot. Turning them on and off mid-match is also dicey at best, since they run a short calibration routine upon startup, which, if the sensor is blocked, renders subsequent readings useless. In short, I think most if not all teams who use this sensor will leave it running all the time.

Sparks

[Al Skierkiewicz]

Dane,
I was trying to be suggestive to use the ability of the sensor to turn ranging on and off as a GP method of interaction with this sensor. From the sheet...

RX – This pin is internally pulled high. The EZ1™ will continually
measure range and output if the RX pin is left unconnected or held
high. If held low the EZ1™ will stop ranging. Bring high 20uS or
more for range reading.

[Sparks333]

Al,

I'm not disagreeing with you - in fact, that technique you outlined is the method by which you chain multiple rangers together. I'm simply pointing out that it's relatively unlikely that folks will implement any sort of control when an open-loop control technique is available, and all it takes is one free-firing sensor to muck up the field for everyone in the immediate vicinity. So, everyone who sees this post, please sacrifice one more digital io pin for ranger control - tell your friends.

Sparks

[ScottW of MaxBo]

Hello, this is Tom Bonar from MaxBotix Inc. If you view http://www.facebook.com/notes/maxbot...77662868954588 numbers 1 and 2; you can see the answer to your question. Please feel free to ask questions on our wall or on the notes thread i linked. As questions come in from the teams we will be rewording and posting the answers to that thread as well as giving the team the direct answer they are looking for.

[Al Skierkiewicz]

Thanks Scott. We know from previous years that the diamond plate that covers the players station can produce significant reflections.

[shutchman]

Where do I legally ...per FRC rules... Get power for the maxbotix sonar sensor?
it's 2.5 - 5.5V.

[engunneer]

Originally Posted by shutchman

Where do I legally ...per FRC rules... Get power for the maxbotix sonar sensor?
it's 2.5 - 5.5V.

The DI/O connections provide 5V on the center (Red) wire.

[shutchman]

A bit more research... The sonar sensor gets wired to one of the analog channels on the NI 9201. Each channel has 3 terminals, 5V, Gnd, Analog IN. Follow the LV MaxSonar pin out connections for the connections to the sonar sensor. Thanks team 122 for this info.

[DominickC]

The EZ1 can also be wired to run in a DIO slot, which is what I've done with mine.

[shutchman]

Ok, thanks. Guess it depends on code you plan on using, analog channel or digital.

[rich2202]

We are using a 555 timer in astable mode to synchronize the ranging of multiple detectors (alternative solution to chaining). You can use DIO to the reset line of the 555 timer to control when the sonar ranges, or allow it to free range at the interval of the 555 timer. We have the 555 timer set to range a little slower than the default rate. Hopefully that will minimize interference with other bots.

We also found the voltage from the Analog board is noisy enough to affect the accuracy of the sensor. Used the capacitor/resistor circuit in the faq to stabilize the power.

One connector from the board to the sonar solves both problems.

How do you use the DIO with the sonar? seems like you would have to use the serial connection, and that is only good for 1 sensor.