Need help deciding on my first robot!!

[Atuss]

Hi
I've been interested in robots for quite some time now and now time has come to buy my first robot. The only problem is I have no experience in this field as such so will need some help on choosing on what to buy for my first robot. I have looked at a few robot kits including these :

Boe-Bots:
http://www.active-robots.com/robots/boe-bots

The RP6 robot system:
http://goo.gl/7iBuk

and the vex system :
http://www.robotiq.co.uk/ccp51/cgi-bin/cp-app.cgi?usr=51F2228097&rnd=7804112&rrc=N&affl=&cip=92.232.237.63&act=&aff=&pg=prod&ref=protobot_kit&cat=vex_starter_bundles&catstr=HOME:vex_starter_bundles

Arduino:
http://www.eeepcssd.com/product_info.php?currency=GBP&products_id=664

There is also the Arduino but I would have to buy all the parts separately and I don't really know all the exact parts that I would need.
At the moment I am leaning towards either Arduino or the RP6 robot because they are programmable in languages very similar to C++ if I am not mistaken, and I know quite a bit of C++ which would make things easier. I want  to create either a self balancing two wheeled robot - with obstacle avoidance at a later stage (this would be done with the Arduino if possible) or a obstacle avoidance robot with the RP6 system with later addition of a robotic arm on top of it. I would rather go with the Arduino as I would love to build the robot from "scratch" as I really enjoy building things, but I would need help on choosing the motors sensors etc. So what should I go with , could anyone help me choose the components if I were to go with the Arduino ?  I would really appreciate it!   I am looking to spend around £200 maximum. Any other options robot systems that I could buy? Also I don't really know where to buy all the parts in the UK other than the active-robots.com, any other places that you would recommend ?? Thanks in advance!!!

[Soeren]

Hi,

Also I don't really know where to buy all the parts in the UK other than the active-robots.com, any other places that you would recommend ?? Thanks in advance!!!

I can't (won't) help you with your decisions, as I dislike such indecision in a buddying constructor, but I can direct you towards some good shops for electronics and in particular the surplus goods:

Greenweld
http://www.greenweld.co.uk

Bull Electrical
http://www.howtocreate.co.uk/tutorials/www.bullnet.co.uk/shops.html

Display Electronics:
http://www.distel.co.uk/

Surpletronics:
http://www.surplectronics.com/

Electronic Surplus:
http://www.electronicsurplus.co.uk/

The electronics section of Anchor Supplies:
http://www.anchorsupplies.com/et.htm

[Atuss]

I dislike such indecision in a buddying constructor

What exactly do you mean ? What is "such" indecision ? I am only undecided because i have no previous experience with robotics, not much I can do about it. I would love to go with Arduino  (meaning buy all the parts separately) as I feel I would learn a lot more and enjoy it more, but then someone would need to help me choose the parts (or just a list of components that I would need to create such robot )and if not i would go with the RP6 as it is a complete kit but then I don't get to put the robot together. I am simply looking for some guidance and others opinion.

[Soeren]

Hi,

What exactly do you mean ? What is "such" indecision ? I am only undecided because i have no previous experience with robotics, not much I can do about it.

There's a lot you can do about it - read, build, fail occasionally, learn - that's how experience is build.
We've all been there at some point, but throwing over the decision of the path to walk is not the way to get ahead.

I would love to go with Arduino  (meaning buy all the parts separately) as I feel I would learn a lot more and enjoy it more, but then someone would need to help me choose the parts (or just a list of components that I would need to create such robot )and if not i would go with the RP6 as it is a complete kit but then I don't get to put the robot together. I am simply looking for some guidance and others opinion.

And (since you asked), it's exactly what I dislike. You throw an important decision away, even though you have already answered it yourself - either you build a kit, which you will be able to do (and learn from that for now), or you give up on the power to choose your own path, by having to rely on strangers and their goodwill to spoon feed you all the way.
It's not something that you learn in a day, week or month, but if you stick to it, reading and experimenting a lot, you'll get there - just don't make the learning curve too steep for you to climb and don't rely on other people being willing to be your personal guide.

Your choice, of course, but at least make it yourself

[Atuss]

Yes but then I need a starting point. Will a microcontroller , couple of motors, ultrasonic sensor, wheels, chassis and a power source be enough for my first robot ? I don't know, and I wouldn't want to fry my robot circuitry just because I didn't know I had to include a capacitor of some sort...

[Soeren]

Yes but then I need a starting point.

Reading this site and other robotics sites is a starting point - when you're confident that you have gathered the knowledge to decide, you're ready - not a minute earlier.

Did you read this site at all??

If you did a little of your own searching, you should have stumbled over the following:
For beginners and The $50 robot

[Atuss]

yes I have read them, but they did not answer my questions. anyways I have decided to first buy a couple of motors and a microcontroller for starters, learn how to control it try things and then gradually buy more things. Now I just need to choose the motor that I shall buy, all websites talk about how to choose the motor - what torque it shoudl have to suit your needs, but non of them can tell me what a good price is for a given motor, so could you help me with that ?

This is the pretty much the only motor that I have found the suits my needs - is geared and had an encoder
http://www.active-robots.com/motors-wheels/dc-motors/gear-motor-encoder.html

but it seems to be quite expensive- and quite overkill for a 2kg~ robot - should I go with it or do you know of other palces that sell similar dc motors cheaper. Thanks for your help so far 

[Gertlex]

To be honest, I've never done a bot where I had to buy the motors myself.  I did one bot with modified servos that turn continuously, and moved on to a walking bot a few years later (college created the time warp between these two bots).  I'd recommend starting with modded servos and a photovore (essentially what the $50 robot is).  The servos you'd use are $10 apiece or less.  Our general point we're trying to beat into you, sort of, is to start simple, and perhaps cheap.  I wouldn't invest in those motors with about a better idea of what I wanted to do than you seem to have.

I'm obviously trying to redirect you a bit. If that's not a satisfactory path for you, that's ok.

[Soeren]

Hi,

yes I have read them, but they did not answer my questions.

Perhaps not, but building this as your first 'bot, you'd have a tutorial to go by and if you got stuck, plenty of users here could help you along.

anyways I have decided to first buy a couple of motors and a microcontroller for starters, learn how to control it try things and then gradually buy more things.

This is the way to progress into building a full blown 'bot.
You'll learn much more this way and as long as you don't continue on, until you feel comfortable using a certain part or technique, you can only succeed

You could start experimenting with some dirt cheap motors, just to get the hang of controlling them - same procedure for larger motors and while you build experience playing around with the small motors, you'll learn what matters most in a motor, the price levels and a lot more that will help you toward your goal.

You also need to learn about materials and mechanics and how that influences the needed motor power.

Now I just need to choose the motor that I shall buy, all websites talk about how to choose the motor - what torque it shoudl have to suit your needs, but non of them can tell me what a good price is for a given motor, so could you help me with that ?

Sure, a good price is when you feel that you got at least your moneys worth of something

The best way to find it will be to find the average price on a given motor as you'll then have a reference to compare against.

It might seem that this is a too theoretical answer, but it depends on a lot of factors - like how many shops sell the motor you need (supply and demand), what quality you need/want, how fast you need it (buying from eg. China might save you a lot, but is slow and can be risky), your available funds etc.

This is the pretty much the only motor that I have found the suits my needs - is geared and had an encoder
http://www.active-robots.com/motors-wheels/dc-motors/gear-motor-encoder.html

but it seems to be quite expensive- and quite overkill for a 2kg~ robot - should I go with it or do you know of other palces that sell similar dc motors cheaper. Thanks for your help so far 

Gear head DC motors are expensive and this one doesn't strike me as overly so.
It will certainly not be overkill - if anything it will be less than kill.
A rated torque (wonder if they mean stall torque) of 1.5kgf-cm means that your wheels should be maximum 2cm in diameter for 2 motors to just be able to propel a limit of 3kg on a flat floor. Any inclination and it will grind to a halt.
You need a good deal more for ~2kg.

BTW. A 2kg robot needs 4 times the motor power of a 1kg robot (speed and acceleration being the same).


While learning all the important parameters that goes into selecting the right motor for a given project, have fun with something cheap - Something like these would be handy for some serious experiments and could be used on a small slow 'bot.


I gave you a number of links to UK vendors that sells surplus motors. Surplus is (usually) new stock and often of pro quality, but sold at prices far below original cost. They often come from companies that liquidates stock for some reason (clearing space, ending a production line or whatever), so the surplus market is where you get the best deals, but not everything is available, so perhaps you have to choose a more powerful motor than you need, or one that is a slightly different shape etc.
Sometimes you find offers too good to pass, even if you don't have an immediate need for a given motor and then you build stock

I grabbed a load of these (non-geared) DC motors from Greenweld about a year ago, as they were (are) really cheap. Shipment to DK was high due to the weight, but still a very good deal.

[Atuss]

Thanks ! Going to buy these then ! : click here as it seems to be a lot better ? than this one and cheaper. i guess I won't be able to use them for a bot as they have high rpm (could use them with some gears ?) but still alright for testing, right ?

I gave you a number of links to UK vendors that sells surplus motors

Yeah I have looked at them but most of the motors really cheap (around £10) compared to this one and I wasn't sure why that is, so my only exploration was that they are no as good. Also non of them have motors that include encoders with them - only option is to buy form outside of UK ? From US and china  ?

[Atuss]

(could use them with some gears ?)

http://www.greenweld.co.uk/acatalog/Shop_Gearboxes_55.html

would one of these do the trick ? (first one in the list)

[Soeren]

Hi,

(could use them with some gears ?)

http://www.greenweld.co.uk/acatalog/Shop_Gearboxes_55.html

would one of these do the trick ? (first one in the list)

That gearbox comes with a motor and the gear ratio can be varied, but to get the other motor to drive it, you'd need to change it a bit to accomodate the larger motor and it would strip the gears in a very short time.
The gearbox with its own motor would be a possible learner on its own though and since you can play with gear ratios, it would teach you some mechanics too.

The gearbox motor combos from the fifth down on the page and further would be nice for a small 'bot and the last two, with the gearbox angled will be easier to mount in a 'bot.
The "120:1 MOTORISED GEARBOX" (second last on the page) would be a good starter as well and at £3.70 won't make a huge cut in your budget.
Two of those would make a fine and cheap differential driven 'bot a la the $50 robot.

When you trade in surplus, you pay less for the same quality. The motor you pointed to initially is not surplus. If you could find the same motor as surplus, it would probably be around the £6 to £10 mark.

My best advice is to start with something cheap to grit your fangs on.
That way, if you ruin something, it won't be too costly and you'll build the same experience.