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Author Topic: Seeedstudio ultrasonic rangefinder  (Read 1645 times)
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Hello,
has anyone ever used this senso----http://www.robotshop.ca/seeedstudio-ultrasonic-range-finder-2.htmlr??
any problems with it??
which of the following ultrasonic rangefinders do you prefer
1)devantec srf05
2)parallax ping)))
3)seeedstudio ultrasonic rangefinder

Im interested because it costs about half as much as the other two,
but if it has problems,ill go with one of the other two.
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ottawa, canada
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I've only used the seeed module so i can't compare but it does work.

As far as i can see it's a clone of the ping.

I am having some accuracy and repeatability issues with my robot but i don't blame the sensor(yet!)
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There don't seem to be too many posts here by people that are happy with robotshop's stuff. And their site sucks. You might get lucky, though.
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There don't seem to be too many posts here by people that are happy with robotshop's stuff. And their site sucks. You might get lucky, though.

Oh geez, I have used Robotshop Canada a number of times and found them excellent for products, prices and shipping.  Now they are close-ish to me so that may account for it.  I actually went to the location near montreal to pick something up (those sensors) and I was delighted at what a busy operation it was.  I'm always happy when suppliers are doing well selling stuff that I like.

I hadn't seen anyone grumping about them here but maybe it's a US thing.  The montreal outfit would certainly be separate operationally although the web site is probably the same software.

Just my opinion of course.
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Thanks guys for the fast reply,,
@bill what sort of accuracy and repeatability issues are you having exactly,could you please expand??

has anyone owned any two of the above mentioned 3 sensors,
which one would you prefer ping or srf05 or seeeduino??
what about accuracy,quality etc etc,
 thanks
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Ok.  I did a little testing as follows
at about 8' I get random jitters of maybe 72 us in the ping time which translates to about 1" or 1%.
at 10" I get occasional 30us errors.

looking at all my data it could be that something is delaying the result of the pulsein by 25us.  That something would have to be happening every 5-10 ms. I've tried bracketing the pulsein with noInterrupts()/interrupts() but the phenomenon is still there.

If you don't hear from anyone else I'd recommend getting the parallax sensor so at least between us we could answer the question.

If this is something in the avr it would be a problem with any sensor but we'd need someone with a parallax or srf to speak up.

As it stands this is not likely to stop my robot from following my cat but the sensor would not be a good choice for an electronic tape measure.



Edit: Thinking about this, the 72us is only 1/2 inch on the return trip or 1/2% and I ca't think of any mechanism for multiple 25us delays on a pulsein.

Edit again: the seeed website gives the resolution as 1 cm which would be around that 70us roundtrip variance.
« Last Edit: November 28, 2010, 02:25:48 pm by bill2009 » Logged

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thanks for the reply
however i don't think there is an error in the pulsin signal,because even
if the pulsin was delayed,the time measured would be only from the
time the pulin signal left to the time the signal was recieved,and
since the resolution should be 1 cm,you are getting about 2.54 times
the error i think,
Please correct me if i am wrong
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since the resolution should be 1 cm,you are getting about 2.54 times the error i think,
well, a maximum jitter of 72us would be 2.4 cm for the round trim so the one way distance is varying by 1.2 cm.

again, doesn't matter too much for chasing your cat but not precise enough for some things.

the ones i've got work fine for me but if i needed real accuracy i'd look at something else.
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There don't seem to be too many posts here by people that are happy with robotshop's stuff. And their site sucks. You might get lucky, though.


Oh geez, I have used Robotshop Canada a number of times and found them excellent for products, prices and shipping.  Now they are close-ish to me so that may account for it.  I actually went to the location near montreal to pick something up (those sensors) and I was delighted at what a busy operation it was.  I'm always happy when suppliers are doing well selling stuff that I like.

I hadn't seen anyone grumping about them here but maybe it's a US thing.  The montreal outfit would certainly be separate operationally although the web site is probably the same software.

Just my opinion of course.

I have had good experience with the US warehouse (which is all it is; you still order from the Canadian site). They are a reseller, so I wonder if Paul is confusing them with some other operation since he refers to "having luck with their stuff". They don't really have much that I would call "their stuff". I used them because they had everything on my list and had the best prices on some of it, giving them the best overall price. It all arrived promptly in fine shape.

I don't like the way their site is laid out and their search algorithm is strange; I always seem to find nothing or half their inventory. But it is usable...
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Hello greasemonkey94,
 
The SeeedStudio Ultrasonic Range Finder (http://www.robotshop.com/seeedstudio-ultrasonic-range-finder.html) is a great sensor and our customers have been very pleased with the quality and price. SeeedStudio products are marketed specifically for use with Arduino, so you can't go wrong. All three mentioned sensors are similar in many respects, with very slight nuances (range, resolution, beam characteristics). For general robotics, they are equally excellent and the choice rests on your personal preference and budget.
 
RobotShop is always open to feedback and suggestions regarding our websites, we do receive many positive comments. The limitations of our website search engine are something we are aware of and plan to rectify. We are constantly working to improve our technology to better serve our customers and make the shopping experience on our websites pleasant.
 
We do have doubts about the justifications behind the claims made by PaulS. RobotShop has countless satisfied customers and represents many leading manufacturers in the industry, all of whom manufacture quality products. We stand behind these products with a world class sales and technical support infrastructure with warehouses in Canada  (http://www.robotshop.ca), the U.S.A. (http://www.robotshop.com/store) and more recently in the European Union  (http://www.robotshop.com/eu). We are also a BBB accredited business, ensuring that we adhere to the highest standards in ethics and customer service excellence.

------------------------------------------
RobotShop
www.robotshop.com
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RobotShop is always open to feedback and suggestions regarding our websites, we do receive many positive comments. The limitations of our website search engine are something we are aware of and plan to rectify. We are constantly working to improve our technology to better serve our customers and make the shopping experience on our websites pleasant.

I have to say, the search really is painful.  I'm just trying to buy wheels and motors and i've given up and gone to the solarbotic site rather than wade thru robotshop.
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I should clarify my earlier comment when I said I didn't like site layout and that search was generally returning way too much or nothing but it was usable. That was poorly worded. The search is pretty much useless. The site layout, which I don't like much, is usable. You have to go into the categories they set up and for Arduino stuff it means paging through a lot of stuff in an almost random order. It might take 5 minutes to find something that I can find in under 2 elsewhere. But once I found my stuff, they did have good prices and sent it quickly. For an initial large order for a project, paging through the stuff was no big deal. For onesie-twosie stuff it drives me crazy.  I did one return - a joystick I hoped would be sturdier - and had no trouble with that. I do tend to use them less than other sites because of the web interface though.
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I should clarify my earlier comment when I said I didn't like site layout and that search was generally returning way too much or nothing but it was usable. That was poorly worded. The search is pretty much useless. The site layout, which I don't like much, is usable. You have to go into the categories they set up and for Arduino stuff it means paging through a lot of stuff in an almost random order. It might take 5 minutes to find something that I can find in under 2 elsewhere. But once I found my stuff, they did have good prices and sent it quickly. For an initial large order for a project, paging through the stuff was no big deal. For onesie-twosie stuff it drives me crazy.  I did one return - a joystick I hoped would be sturdier - and had no trouble with that. I do tend to use them less than other sites because of the web interface though.

very well put.  i like robotshop canada very much.  They have great selection, good prices, and quick delivery.

I had never thought about the search before you brought it up but it is the worst aspect of the site. I may actually call them monday to see if they've got the wheel motor combo that i want rather than actually go thru the hassle of a new supplier.
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back to the rangefinder.  It's worth noting that this device has a fairly long cycle time.  The documentation says you can call it every 50ms but, at least with my two samples, it needs 66ms between calls.  

This might not matter too much in some instances but my carbot is moving at 100 in/sec so it's traveling 6 inches between pings and that's not even very fast.

The issue is some combination of the speed of sound and the code in the sensor.  Other sensors also say 50 ms between calls but i don't know how they perform in practice.

If you really needed tight timing you'd need a different technology or better code.

Also, note that the standard code for all these sensors uses pulsein which stalls your code until the sensor responds.  In the case where the sensor doesn't get an echo that can be up to 40ms.  Again, painful in a moving bot.
« Last Edit: December 07, 2010, 09:20:51 am by bill2009 » Logged

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I think the range finder is great. I got one recently from seeedstudio and I can get +-2 maybe up to 4 mm accuracy. Remember ultrasonic rangers won't deliver good measurement if there are a lot of stuff around or it's mounted too close to the floor. The sound easily reflects and you get jitter. My estimation is a ranger sitting on table top pointing at the ceiling.
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