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(...) I was the one that mentioned that I couldn't find a way from the SW I have to turn the US sensor off. That said, I don't think it's time yet to worry about intractable problems: A hundred of us or so have been playing with this stuff for a (...) (19 years ago, 21-May-06, to lugnet.robotics)
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| | Re: Ultrasonic sensor interactions
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(...) Wow! That's a lot lower than I'd have expected - at that frequency there is a good risk of harmonics from normal sound interfering with it. (...) Right - 350 meters per second is pretty slow by computer standards. (...) (Not to mention things (...) (19 years ago, 21-May-06, to lugnet.robotics)
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| | Re: Ultrasonic sensor interactions
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(...) The device operates at 40kHz, the transmit and receive piezo devices are only resonant at that frequency. Even though the measurement period is short (time from transmit to time to receive) it is necessary to wait quite a while for the sound (...) (19 years ago, 21-May-06, to lugnet.robotics)
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| | Re: Ultrasonic sensor interactions
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(...) The 'Aloha' protocol was the predecessor of this. (...) Someone earlier told us that the thing runs all the time and can't even be shut off. That being the case, I think we're pretty much doomed. (...) Yes - but the relatively low frequency at (...) (19 years ago, 21-May-06, to lugnet.robotics)
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| | Re: Ultrasonic sensor interactions
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(...) How about a single computer that was Bluetooth accessable. The server could act as a "lockable" resource that a NXT could acquire prior to doing the US detection. Then the NXTs don't need to know about each other, just the main server (and it (...) (19 years ago, 21-May-06, to lugnet.robotics)
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| | Re: Ultrasonic sensor interactions
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The problem here is the management of a single shared resource, i.e. the air through which the ultrasonic signals travel. The lack of a Bluetooth broadcast mechanism makes the implementation of a conventional resource locking system difficult, but (...) (19 years ago, 21-May-06, to lugnet.robotics, FTX)
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| | Re: Ultrasonic sensor interactions
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(...) This is a great idea except for one very important item: there is no such thing as a broadcast message (ie: a message sent to everyone) using Bluetooth. So for any such system to work, each robot has to know about every other robot, and send (...) (19 years ago, 21-May-06, to lugnet.robotics)
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| | Re: Ultrasonic sensor interactions
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(...) The problem with that is that both NXT machines may be listening. Neither hears anything - so both decide to emit a ping - and they still interfere with each other. The nasty part is that even if you can detect that an interference happened, (...) (19 years ago, 20-May-06, to lugnet.robotics)
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| | Re: Ultrasonic sensor interactions
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(...) A better alternative would be to develop protocols in which the NXT controllers use their communications to tell each other what they are about to do. If you can sent a message that says "I'm about to do an ultrasound 'ping' - so you'd better (...) (19 years ago, 20-May-06, to lugnet.robotics)
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| | Re: Ultrasonic sensor interactions
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(...) Very feasible... IF you could turn the US sensor off. As near as I can determine, the US sensor, when connected, is never off: it is always emitting a series of "pings" (you can actually hear a "click" from the sensor if you are really close). (...) (19 years ago, 20-May-06, to lugnet.robotics)
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| | BrickFest Bulletin: Mindstorms/Technic Contests and Events, Space Contests, Castle Contest and..
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(URL) Mindstorms/Technic Events BrickFest 2006 is fast approaching! This year, the Technic and Mindstorms Theme coordinators are pleased to announce 5 competitions. The competitions will be spread across the 3 days of BrickFest. The planned (...) (19 years ago, 20-May-06, to lugnet.events.brickfest, lugnet.events, lugnet.robotics, lugnet.robotics.events, lugnet.space, lugnet.castle, lugnet.general, lugnet.announce, lugnet.build.contests, FTX) !!
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| | Re: Ultrasonic sensor interactions
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Hi Tim, (...) it should be possible to use the ultrasonic sensor itself for that, there is a command to listen in on other sensors for that purpose. Jürgen (19 years ago, 20-May-06, to lugnet.robotics)
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| | Re: Ultrasonic sensor interactions
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(...) How feasible would it be to set up some sort of time-sharing communications over Bluetooth to allocate time slots when each of the robots in an area would be allowed to use their ultrasonic sensors? -Tim (19 years ago, 20-May-06, to lugnet.robotics)
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| | Re: Ultrasonic sensor interactions
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(...) In a word, multiple ultrasonic sensors can be a problem. This is a general problem and not specific to Lego ultrasonic sensors. Pulses emitted by "the other sensor" can arrive at just the wrong moment, creating a false range reading. Clever (...) (19 years ago, 19-May-06, to lugnet.robotics)
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| | Re: RCX Virus?
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(...) But (critically) not ALL of the stuff! (...) What I suggested was that your rechargable batteries are at the end of their lifespan. Buy a set of regular NON-RECHARGEABLE batteries and see if everything works OK then. If it does then toss out (...) (19 years ago, 19-May-06, to lugnet.robotics)
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| | Re: RCX Virus? - battery output and RCX performance
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(...) I think that NiMH should be up to the task at that power level (difference between NiMH and NiCd occur at much higher discharge rate). But maybe there is one or more dead cell that cant't hold its charge? Since NiMH provide 7.2V instead of 9V, (...) (19 years ago, 19-May-06, to lugnet.robotics)
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| | Re: RCX Virus? - battery output and RCX performance
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(...) The Lego geared motors can pull about 250 mA when stalled, and close to that when heavily loaded. So for three motors, that may be more current than your batteries can deliver. Rechargeable batteries, esp NiMH, don't deliver the same peak (...) (19 years ago, 19-May-06, to lugnet.robotics)
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| | Ultrasonic sensor interactions
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Can someone from the MDP comment on how multiple robots using the ultrasonic sensor interact. It is possible to use this sensor reliably when one or more other robots nearby are using theirs? -Tim (19 years ago, 19-May-06, to lugnet.robotics)
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| | Re: RCX Virus?
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ok, I finally got to trying some of the stuff you recommended. I recharged the batteries and tried downloading the firmware. It can run the whole program without the motors being plugged in. It can even run the program with all motors plugged in but (...) (19 years ago, 19-May-06, to lugnet.robotics)
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| | Re: Thoughts
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Hi Andrew, (...) there are actually 3 I/O lines on each sensor port: - 1 legacy sensor A/D with appropriate power supply on the same line. - 2 digital I/O lines, one of which can also be configured as analog in. The remaining lines are 2 GND pins (...) (19 years ago, 19-May-06, to lugnet.robotics)
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