ultrasonic sensor rotation mounting?

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ultrasonic sensor rotation mounting?

Postby circuitmage » 14 Jan 2013, 15:37

I want to get a nice mount and placement for a 60 degree scanning ultrasonic sensor on my bot.

My first attempt used an NXT motor and 2 gears to mount the ultrasonic sensor, which worked, but just looked bulky and awkward. Made for poor placement.

Over the weekend, I built a direct drive using the older RCX 71427 motor. But still have to build a mount.

Any other ideas?

Thanks in advance!
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Re: ultrasonic sensor rotation mounting?

Postby circuitmage » 15 Jan 2013, 14:17




http://youtu.be/mrdh5F3QiEs

So, this is my 3rd version. I didn't want to use the older motor afterall, as the encoder is too nice to pass up, but I've noticed mounting the NXT motor always seems abit awkward. Maybe another reason to look forward to the new set coming out!

Hmmm..youtube embedded is not working ??....
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Re: ultrasonic sensor rotation mounting?

Postby mattallen37 » 16 Jan 2013, 00:16

I would suggest gearing down if anything. You have that geared up 7.5 times, so with backlash and less than perfect motor PID, you'd be lucky to get 15 degree accuracy.

YT embedding works with some browsers, or so I've heard. I only use Chrome, and it doesn't work.
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Re: ultrasonic sensor rotation mounting?

Postby jwiger » 16 Jan 2013, 01:43

Works on Firefox. And I agree with Matt, best bet is to mount the sensor directly to the servo output. Eliminating gears eliminates backlash.

Here is an idea for you:
http://www.dexterindustries.com/Project-dradar.html
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Re: ultrasonic sensor rotation mounting?

Postby circuitmage » 17 Jan 2013, 17:38

When I embedded the YT video, it did not show up, even when I went back to look at my post. (Chrome)
Now, it shows up. Hmmm....

I was not really concerned about precise movement. I need to compare the gearing with the encoder. From my first tries, the encoder is fairly accurate but I would like to see what it does with this gearing just for fun.

One reason to use the gearing is to reduce motor use, and the other reason was to get it mounted (aesthetically) as I wanted. One more reason, moving gears just look cool. :)
I DO need to work on the gearing though, if I keep them.

I like the Dexter version, did not think of mounting it like that. And logging the data would be interesting.

Great suggestions there, thanks for the feedback.
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Re: ultrasonic sensor rotation mounting?

Postby mikebittmann » 03 Feb 2013, 20:19

I mounted mine using the third servo (between the drive motors) and a worm gear turning a 24t spur gear. Turns slowly but very reliably. the spur gear is on the bottom of a vertical axle which places the US over the right front corner of the robot. It turns about 45 degrees in either direction and then the robot goes in the direction of least resistance.
\Mike :)
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Re: ultrasonic sensor rotation mounting?

Postby circuitmage » 04 Feb 2013, 14:18

A few weeks ago, I moved my assembly to the front, as you described, but kept my gearing. Because of the size and type of gears I was using, it was not a very good connection. Fast, but not good.

Last night I switched over to what you suggested, worm gear and 24t, and it's working much better. My only complaint (the way I set it up), is that my axle out of the motor that has the worm gear has about a 1-2 mm loose swing at the end (I used the 6 or 8 stud size axle). I can improve that by holding down the end, though, but it is still working better than before.

Otherwise, great suggestion. The 24t is much slower but creates a stronger mechanism. When I had my smaller gears on , they would slip (due to the wire on the back of the US sensor) at about 30 degrees. This one can spin around 360 without a problem, even with the wire attached.

Suggestion appreciated...One small step...
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