chriglu
Posts: 27
Joined: Thu Mar 28, 2013 10:17 pm

Beginner questions - first robot

Wed May 01, 2013 6:25 am

Hello

After some fun with my bird-watching-project i would like to dive into robotics and build my first robot :-) I would like to create a very basic robot which i can improve over time with new abilities and sensors to get used to this new world. I tried to find out all the abilities i would like to add.

Abilities
- Drive around (2 continuous servos)
- Avoid obstacles (Ultrasonic Ranging Module)
- Record/Stream Images/Videos (Webcam)
- Voice/Face recognition (Webcam/Webcam-Mic)
- "Stand-up" and balance itself on two wheels (Accelerometer&Gyro)
- Audio feedback (Small Speaker)
- Remote Control (Wlan/Bluetooth)
- Powered with cable

Optional Abilities
- Detect movement in room and drive to it (Motion detector)
- Battery powered
- Temperature sensing

I am not sure about the design yet, but i think it should look like something between a 3-wheeled-robot (http://goo.gl/8MnGb) and a balance-bot (http://goo.gl/FRWu8)

Equipment needed
- Raspberry Pi
- Raspberry Pi Breakout Kit
- Robot Chassis with three wheels (2xbigger, 1xsmaller)
- Ultrasonic Ranging Module (HC-SR04)
- Accelerometer & Gyro (?)
- Webcam (Old Logitech Webcam)
- Servos (?)
- Wlan/Bluetooth USB-Dongle

Optional Equipment needed
- Motion detector (DYP-ME003)
- Battery
- Temperature sensor (DS18B20)

My questions so far :-)
- Is this all possible with the RaspberryPi itself or do i need other things to drive all this equipment
- I've listed a few part numbers, are they ok? alternatives?
- Is a servo the right kind of motor for my purpose
- What programming language is best for all the abilities
- Should i get the parts and just start somewhere and get excited or plan everything exactly how it should work?

It doesn't matter if this isn't going to be a perfect robot. The main goal is to learn and improve my skills and have loads of fun :) Thank you very much!

Ravenous
Posts: 1956
Joined: Fri Feb 24, 2012 1:01 pm
Location: UK

Re: Beginner questions - first robot

Wed May 01, 2013 2:03 pm

Wow that's quite a long list - to answer your last question I would get the basic thing working first and build a simple Mark 1 version. Don't try to plan the entire thing in advance, you are certain to find some things don't work in the way expected and you'll need to rebuild things part way through.

I'm not sure if continuous rotation servos will work for the balancing robot, I get the impression they need a combination of speed and torque, and servos are geared down a lot so might not be fast enough? But they should be OK to build a basic two wheel, one slider, chassis first.

Running it off a tether cable at first is a good idea - it'll save you the trouble of selecting batteries at the start. You can think about those later when you know how heavy it's going to be.

Congratulations on the nestbox & birds by the way!

mikerr
Posts: 2800
Joined: Thu Jan 12, 2012 12:46 pm
Location: UK
Contact: Website

Re: Beginner questions - first robot

Wed May 01, 2013 2:21 pm

It's much better to start with a simple rover bot, and work upwards...
Ravenous wrote:I'm not sure if continuous rotation servos will work for the balancing robot, I get the impression they need a combination of speed and torque, and servos are geared down a lot so might not be fast enough?
They're easily fast enough for a balancing bot, here's mine using continuous servos:

http://www.youtube.com/watch?v=GNenQ4OWgSM

That's without an accelerometer or gyro - just using a distance sensor to the floor - which was just barely accurate enough.
Last edited by mikerr on Wed May 01, 2013 3:19 pm, edited 1 time in total.
Android app - Raspi Card Imager - download and image SD cards - No PC required !

Ravenous
Posts: 1956
Joined: Fri Feb 24, 2012 1:01 pm
Location: UK

Re: Beginner questions - first robot

Wed May 01, 2013 3:08 pm

Good answer! :D

chriglu
Posts: 27
Joined: Thu Mar 28, 2013 10:17 pm

Re: Beginner questions - first robot

Wed May 01, 2013 5:04 pm

Ravenous wrote:Wow that's quite a long list - to answer your last question I would get the basic thing working first and build a simple Mark 1 version. Don't try to plan the entire thing in advance, you are certain to find some things don't work in the way expected and you'll need to rebuild things part way through.

Congratulations on the nestbox & birds by the way!
Thank you very much! I just put it all on the list what i've got in mind :-)
Do you think i can use the Rasperry Pi or should i better buy an arduino kit?
mikerr wrote:It's much better to start with a simple rover bot, and work upwards...
They're easily fast enough for a balancing bot, here's mine using continuous servos:

That's without an accelerometer or gyro - just using a distance sensor to the floor - which was just barely accurate enough.
Can you tell me which servos you used? So i can get a feeling for mine

LinuxCircle
Posts: 26
Joined: Sat May 04, 2013 2:03 am
Contact: Website

Re: Beginner questions - first robot

Mon May 06, 2013 3:46 am

Hi,

For the chassis, you need something like 4WD chassis. You need DC motors to run the wheels instead of Servos. Servos is for steering wheels, or pan & tilt or anything that you need high degree of rotation accuracy. If you are building a racing RC than you need a brushless servo. But for basic rover, DC motors are the best to learn about moving backward and forward.

For the micro controller I used DFRobot Romeo V2, which has USB, and Arduino compatible. So you dont have to pull your head out trying to write interfaces for your GPIO pins using Python etc.

The best tutorial for Raspberry Robotics can be found here: http://www.linuxcircle.com
Just follow the instruction and modify the source code to suit your needs. ;)
www.linuxcircle.com

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