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PedroR
07-02-2009, 09:18 AM
Hi all

We guys on the other side of the ocean got a new Arduino Wheeled Robot kit from Inex.


http://robosavvy.com/RoboSavvyPages/Inex/POPbot/POPbot_description_without_price.jpg
It is here http://robosavvy.com/store/product_info.php/products_id/547

What is your opinion on it? I do find it a nice proposal considering the price.

Are you guys getting it on trossen as well?

Also, in my case I was considering using an I2C compass for navigation but someone was saying that these are very prone to errors when we hit bumps...
Is this a fact? What is your opinion on it?

Regards
Pedro

lnxfergy
07-02-2009, 09:30 AM
Personally, it looks like a not-so-clean, and slightly more expensive version of the 3PI... it appears some of the I/O may be brought out better though (which is my main gripe with the 3PI, you can attach say a GP2D12 to it without soldering)...

-Fergs

Adrenalynn
07-02-2009, 11:33 AM
Wow. Do you want an honest opinion? This is a shipping commercial product and not something put together by a first-time robot builder?

lnxfergy
07-02-2009, 06:47 PM
Also, in my case I was considering using an I2C compass for navigation but someone was saying that these are very prone to errors when we hit bumps...
Is this a fact? What is your opinion on it?

Ok, so on the robosaavy site they have this quote: "Add an I2C compass (http://robosavvy.com/store/product_info.php/products_id/394) and it will always know where it's headed" I don't even know where to start here. That's so entirely untrue. A digital compass, like any compass, but especially the digital ones, will be thrown off by any magnetic field. A robot, has tons of (time-varying) magnetic fields. Unreliable when "we hit bumps" is probably more of an issue that the robot's motors have to pulse up, causing a magnetic field that throws off the compass. Or, it might be that the compass dips out of the horizontal plane. Either way, a digital compass will not make it so your robot "always knows where it's headed". You'll have to add back end processing to keep track of where the robot has been, what the readings were, and what the motor outputs have been, then you can, with some probabilistic certainty know where you are headed.... Unfortunately, there are no magic sensors out there, they all have issues.

-Fergs

DresnerRobotics
07-02-2009, 08:06 PM
As the 'buyer' for Trossen, I don't see much point in picking it up when we already carry the 3pi. It's more expensive and nowhere near as polished. As Fergs said, the only thing about the 3pi is that the I/O isn't as easily accessible, however a $20 breakout board fixes that, and it would still be less expensive.

I'm sure some people out there will like it, but it fills the same slot as the 3pi for us, and we try not to overlap products too much.

PedroR
07-03-2009, 11:51 AM
Hi guys

Thanks for all your feedback.

It was very important for me to understand a number of things.
Let me explain:

1) The main target of the product is actually the Education Market. The manufacturer (Inex) has a very broad portfolio of robot kits for education. (maybe that's why the kit comes with such bright colours.... LOL): All sensors (the included ones and the optional ones) use JST connectors to avoid the need for soldering; it also comes with activities manuals that help teachers and students learn with the robot, etc.

We actually have another kit from them (similar but based on ATMEGA8 with less option parts/extras) which is quite popular.



2) From your comments I now understand this platform isn't very appealing to power users given there is the 3pi.
Indeed the 3pi is a very nice product - and surelly much better suited for power users given the great quality DC motors it employs - but it is not RoHS complaint and thus it is a serious risk to sell it in Europe (so we can't really do it).



3) As for the compass and other navigation techniques, this issue has also been brought up in the Robosavvy forum.
I've learned that a gyro is an important addition to these platforms to account for all the issues of not navigating levelled: the issues with the compass that you mention, the issues when you go over a bump where the actual horizontal distance is less than the one measured by the wheel, etc.
A wheel encoder is also something that was mentioned but that option exists for these robots.
This combination was aimed at using "gyrodometry".

Someone also mentioned the use of Accelerometers although I still don't understand how you sue the information from these. Are they to account for the cases when only one wheel slips and you have centrifugous acceleration?

A final mention to the Arduino board it includes: the board is a bit expensive when purchased stand alone but it does expose all IO nicelly as Inxsfergy noticed. This one adds for example, support/connectors for 2 PWM servos in addition to the 2 dc motors; not sure about the 3pi though; probably has it was well.

As a sidenote pricewise you guys in the US usually get better end user prices. In Europe we always end up with higher end user prices mostly due to the heavvy VAT which in our case makes prices 15% more expensive...

Once again, thank you all for your feedback.

And Andrew, thank you too. I hope we can keep talking on both forums ;)

Regards
Pedro.

LinuxGuy
09-04-2009, 11:26 AM
I've been researching various controllers, and ran across the RoboDuino as an Arduino clone. I am hoping there will come kits based on the RoboDuino since it is designed for robotics and has all the nice 3 pin headers for sensors and devices. This should solve some of the short comings of using Arduinos for robotic projects. I'll eventually be using one or more RoboDuinos for specific processing tasks on my robot.

8-Dale

DresnerRobotics
09-04-2009, 11:37 AM
Yup we carry the Roboduino here (http://www.trossenrobotics.com/roboduino.aspx), I prefer it over the Arduino simply for ease of use. No need to breadboard; sensors and servos can plug right in.

LinuxGuy
09-04-2009, 11:49 AM
Yup we carry the Roboduino here (http://www.trossenrobotics.com/roboduino.aspx), I prefer it over the Arduino simply for ease of use. No need to breadboard; sensors and servos can plug right in.
Yep! I'll probably get one of them next month. I've been wanting to use an Arduino for robotic projects ever since I got my first one, but the fact of not being able to connect standard servos and sensors to it easily has put me off from doing that.

I've done some breadboarding with my Arduino and Sanguino, and have had servos connected to them, but I consider it a pain to wire everything up. I've had my Arduino connected to up to 6 servos so far and written what I consider a better software PWM library. The RoboDuino will make this MUCH easier and I'll be using one to handle processing for my 3-axis accelerometer and other things for W.A.L.T.E.R.

8-Dale

lnxfergy
09-04-2009, 12:12 PM
I've had my Arduino connected to up to 6 servos so far and written what I consider a better software PWM library.

Take a look, but the new Arduino 0017 release includes a hardware servo library that can control 12 servos.

-Fergs

LinuxGuy
09-04-2009, 12:24 PM
Take a look, but the new Arduino 0017 release includes a hardware servo library that can control 12 servos.
I'm not fond of using an Arduino to directly control servos. I prefer to use an SSC-32 servo controller for that. :) It's got many more features and just makes controlling servos so much easier, including group and timed moves. I did keep the servo controlling aspect in the newer PWM code I've created (based on another library), but I created it mainly for PWMing other things like LEDs and such.

8-Dale

lnxfergy
09-04-2009, 12:34 PM
I'm not fond of using an Arduino to directly control servos. I prefer to use an SSC-32 servo controller for that. :) It's got many more features and just makes controlling servos so much easier, including group and timed moves. I did keep the servo controlling aspect in the newer PWM code I've created (based on another library), but I created it mainly for PWMing other things like LEDs and such.

8-Dale

I never said the Arduino was a replacement for the SSC-32, I just mentioned the new library exists, as you seem to imply you didn't like the old one.

-Fergs

LinuxGuy
09-04-2009, 01:03 PM
I never said the Arduino was a replacement for the SSC-32, I just mentioned the new library exists, as you seem to imply you didn't like the old one.
I understand your meaning. :) I just didn't like the way the original library did some things, and I wanted to change one or two things and add a couple things I didn't see for what I wanted to do. The original library gave me a good jumping off point for my own stuff. :)

8-Dale