I’m thinking of a design that would use an ultrasonic range finder/ proximity sensor to determine where the spider leg is during autonomus scoring…
But I have no idea if they are legal this year? I think 71 & 1 used the vex model last year to sense weather there was a ball at a sertain part in their robot last year…
They are legal, provided they fit all criteria in the flow chart.
As long as they follow the flow chart, they’d be fine.
On a side note, you may want to look at possibly using IR range sensors as an alternative to the ultrasonics if they have characterstics you don’t like. That looks like the route we’re going, since we don’t like the wide field of view of the ultrasonics.
Yes, the VEX units are legal in FRC. They are excellent for detecting objects infront of your robot. You just need to change the connectors to female for the FRC controler. That or make a female-female cables so you don’t have to modify the sensor. They are excellent for detecting metal 10" disks infront of your arm. There are drivers avalible for it in easyC and MPLAB.
What about third party sensors?
also, is it possible to detect the edges of the spider feet with this type of sensor?
or is it just goigng to read a distance off to the controller?
We also are considering using sonic range finders.
At the top of our list is this one:
You may also wish to read this thread discusising some testing of it.
I’ve done mostly the same testing as the thread with similiar results.
Ultrasonic range finder/ proximity sensors may be use as long as they meet all other rule. Check the flow chart.
The MaxSonar-EZ1 looks like a really nice sensor. It has an option to return analog voltages so it should be extreamly easy to use. Plus it doesn’t eat precious interrupt ports. Looks like I might have to pick up a new toy to play with. 
I too would like a Maxbotix sensor…(drool)…but I’m a little leery about buying from a distributor I have never heard of.
Does anyone here know of a reputable distributor of this type of sensor, or an IR distance sensor? I am interested in getting one, but I don’t know where to look. Parallax has one, but its range doesn’t seem high enough for the application I have in mind.
Thanks,
JBot
If it’s any comfort, team 246 ordered a Maxbotix sonar sensor, and had no problems with the vendor. It’s a very nifty sensor. It’s pretty accurate, and very easy to set up.
Toby
This sensor looks good but I do have some qualms about using the ultrasonic sensor. First of all there are potentially way to many things that the signal could bounce off of and secondly if any other robot is using ultrasonic sensors they have a good chance of interfering with each other.
Those of you who purchased one, care to share any test results(preferably on the rack)?
So, lemme get this straight. We can use up to, but not including 900 mega hertz (or however you spell that, you get the drift). Does this include any camera? Can we use military-style cameras? Or is that out of the question?
If Chuck is right, that’s insane :yikes:
Yeah they should be legal, a few teams that saw last year bought some Vex Ultrasonic Sensors and used them without problems. The Vex sensors are great and if you don’t use them on your FRC robot, you can use them on your Vex robot!
Yeah, I’m gonna get some military sensors and our robot is gonna home in on the spider like… a bomb. Hehe!
The Maxbotix sonar sensors are available from Sparkfun, who is a pretty large hobby robotics distributor, so I’d say there at least decent if Sparkfun is willing to carry them.
As for IR Range sensors, you can get ones made by Sharp (easily the biggest maker of them) from either Acroname or Digikey. Just search for any of these companies and you’ll find their websites.
See http://www.chiefdelphi.com/forums/showthread.php?t=46912
How very true, you have hit upon their greatest weaknesses.
Not sure what you refer to, but ultrasonic (sonar) sensors (the subject of this thread) operate in the high audio range, far far below the Radio Frequencies you mention. Use the flowchart to determine what is legal.
Don
um ultrasonic is still sound, which is pressure waves, radio is electro-magnetic waves… Sound waves won’t ever interfere with radio waves, no matter if the “frequencies” are the same.
If you are going to use ultrasonics, be careful, for a number of reasons.
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Try to keep the sonic environment relatively “closed”/“close”. By that, I mean just as with active IR rangers, the more localized the sensor’s effect, the better. Example: Sensing the spider’s endplate with something on your gripper is OK. Blanketing the entire field with a slew of ultrasonic sensors pointing in all directions looking for the rack is questionable. The latter is prone to interference from reflections, and background noise. It could also potentially interact with other robot’s sensors. This is not only Ungratious, it could cause a judge to rule your sensor system illegal.
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Be aware that pneumatic venting “whistles” loudly in the ultrasonic. If your sensor is anywhere near a venting pneumatic’s air output (yours, a partner’s, OR an opponent’s) , it can potentially be swamped out by the “dog whistle effect”. (Yet another reason to keep your sensing “local”.) Verify your sensor(s) aren’t affected by your pneumatics venting.
If they are affected, there are some simple things you can do about your OWN interference:
A) Point your valve’s vents away from your ultrasonic system. That may be sufficient to prevent interference.
B) If (A) isn’t sufficient, combine all of your pneumatic vent outputs together with T-connectors and add a foam “muffler”/“silencer” to the resulting output vent tube. They’re COTS - search for “pneumatics muffler”, “air exhaust silencer” etc…
C) **Run a short “exhaust” vent tube to/toward the far end of your robot and point the pneumatic exhaust opening away from your sensor system.
D) Do both B&C **(locate a pnaumatics muffler far from your sensors).
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3) The PIAB vacuum generators MAY swamp out ultrasonics for this contest! I haven’t tested them, but venturi vacuum generators must vent constantly to work at all. Ultrasonic systems on your robot MAY then be hearing nothing but serious dog whistles from a significant number of bots on the field in every round.
Anyone happen to have the equipment to check to see if they whistle anywhere near 40 KHz? (That’s roughly where most ultrasonic systems run.)
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I hope this helps!
- Keith