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[on:]

Hi,

I just dived into the Arduino world and want to create a little robot car with an ultrasound sensor mounted on a servo, and using a stepper motor to keep track of the car's movements. (+ some algorithms to make sense of all that)

The big problem I have now is determining which motors to use:

. The perfect choice for the servo would be the Tinkerkit Servo ( http://snootlab.com/tinker-it/231-module-micro-servo-tinkerkit-fr.html ) because I'm ordering a lot of stuff from that shop and that's the only servo they got. But ... I guess we can't use a Tinkerkit servo without a Tinkerkit shield, right ? (I'll be using the Adafruit motor shield)

. For the stepper motor, I need to be as precise as possible, in a reasonable size (that can fit in a little car, not a *real* car's stepper motor   )

The motors shouldn't be too expensive. Like ~30€ max for both of them if possible (if it's just a little more, I could cope with it)

Any ideas ? (including websites where I could buy those; FYI I live in France)

[Reply #1 on:]

I am just starting the very same project after getting interested in Arduino.  You should check out dx.com, I got everything I need for the project for 40 euros + free shipping.  Only downside was it took 4 weeks to get here ( Finland ).  Anyhow just make sure you know the angle of the servo, mine does 180 degrees, which is good, but I have heard that some only do 120.  Depends what you want.  I just got some generic motors and they are speeding across the floor + you can control the speed of them with a L298N controller.  Good luck.

[Reply #2 on:]

Oh, that's great bobo ! Could you send me your mail by private message ? I'd have some questions I'd like to ask.

Also, the components I chose would cost around ... 130€ ! So I'm surprised that you could find all what you need for only 40€ (or was it just the motors?!).

Anyway, I'd be very glad if you could give me the REF. of the motors you chose :-).

Happy to see I'm not the only one interested by those kind of robots (and hope you'll do great with your project !)

[Reply #3 on:]

This is what I got:

Chasis -- Mine had two layers but it seems they don't sell that anymore.  This is quite close to what I have and the motors seem the same.

http://dx.com/p/smart-robot-car-chassis-kit-for-arduino-transparent-yellow-152984  16euros

Bluetooth module  --  I am using a mobile phone as the controller.  You just need to set up a serial port.

http://dx.com/p/jy-mcu-arduino-bluetooth-wireless-serial-port-module-104299?rt=1&p=2&m=2&r=3&k=1&t=1&s=152984&u=104299  7euros

L298N motor controller --  Get a separate battery pack too to run the motors, I have been using 9v (6 AA in series).  I have heard they don't cause a big voltage drop like a 9v battery

http://dx.com/p/l298n-stepper-motor-driver-controller-board-for-arduino-120542?rt=1&p=2&m=2&r=3&k=1&t=1&s=104299&u=120542 5 euros

The ultra sonic sensor

http://dx.com/p/hc-sr04-ultrasonic-sensor-distance-measuring-module-133696?rt=1&p=2&m=2&r=3&k=1&t=1&s=152984&u=133696 3.50 euros

And a servo to move the sensor around, I think I got this, not sure anymore.  But very similar.  Mine had a bracket.

http://dx.com/p/sg90-mini-servo-with-gears-and-parts-2kg-torque-35764?rt=1&p=2&m=2&r=3&k=1&t=1&s=133696&u=35764  3,50

DX also sell some kits, they're quite cheap too.

And I got some Arduino of Amazon for about 10.  It's a good idea too to buy some dupont leads.

So far I have got the car to move around via bluetooth and I have managed to control it's speed.  I am just working on the servo and the sensor.  I also plan to have some kind of autopilot mode where the car will move around the house by itself just using the sensor as a way not to crash.  Let me know if you need help.  One major drawback with dx is that you will get no documentation, the internet though has pretty much all you need to know so it may not be a problem.

[Reply #4 on:]

Thank you for those links

I think mine is really expensive because I want to use a WiFi module (which costs ~70-80€) and an Arduino Mega (from Ebay: 25€) + an expensive sensor (25€)

I noticed you used the chassis with the built-in (DC) Motors. Any idea if those motors can be easily changed for stepper motors ? (actually, I bought the exact same chassis ! But I bought it from a chinese seller on ebay and I won't get it before 6 or 8 weeks) ; If you know any stepper motor with a good precision (but adapted to a robot like the one you're building), it'd be welcome !

[Reply #5 on:]

That L298N controller module can only handle one stepper motor, you would need two therefore.  One drawback with that chassis I got is that the motors have no markings on them, I have no idea about their spec.  I have been using 9v and it seems OK, 5v from the Arduino made them run very slow.  But I don't see why you could not screw on two stepper motors after that.  If you use Wifi does that mean you can only control it via the computer?

[Reply #6 on:]

One extra thing, if you do buy that controller then this will be useful.

http://www.geekonfire.com/wiki/index.php?title=Dual_H-Bridge_Motor_Driver

IMO: just buy some stuff and play around, if you fry a thing or two what have you lost?  You're only down 2-3 euros and your intelligence has increased

[Reply #7 on:]

You could control it with WiFi from your phone too (what sucks is that the WiFi shield can't be used as a host, so you have to configure it to connect to the right WiFi spot each time).

I'll be using the Adafruit Motor Shield which should manage all the motors I'm using, hopefully.

I still don't know which kind of stepper motors I should choose :/ The specs don't mean anything for the beginner I am.