Let's Make Robots!

First Bot 1.1

Navigate via infrared.

Above

Front

I had been learning basic electronics and the use of Arduino in college this year to create musical instruments and interfaces. Now that summer is here and I have time on my hands I decided to put my new knowledge to use.

I started out by buying an Arduino beginner set from Oomlout which had a mini servo and toy motor included. Once I was comfortable with how those worked I started to look for the parts I needed to build my robot. I went with the tamiya tracks and gear box because of the price. Also it would allow me to use different track shapes and the base plate allows for easy attachment of other things. After buying these I then had to start buying some capacitors, H bridge motor controllers, hex spacers and lots of nuts and bolts. Due to my inexperience I ended up spending a lot more than I should have on things that I couldn't actually use or didn't need...  but at least I wont be short of H bridge chips in the future as I currently have five...

My robot is essentially based on this one..

http://luckylarry.co.uk/arduino-projects/obstacle-avoidance-robot-build-your-own-larrybot/

Like him I swapped the motors that came with the gearbox for a pair of Solarbotics GM3 which draw less current and used the SN754410 H bridge which can supply more current to each channel than the L293D. I think...

 

At the moment the main thing holding this robot back is a lack of power, both for the motors and the arduino. The motors struggle when making turns on carpet and the 9V battery cannot supply the arduino with enough power to run itself, the H bridge logic supply, IR sensor and the mini servo. So for the time being the mini servo is not used. I think the motors will be fine if I give them 6 AA batteries instead of the 4 x 1.2V  that they have at the moment. I am not so sure about how to supply everything else with power though so any suggestions would be appreciated. Should I use a battery to power the arduino and a seperate supply for all the other components?

Unfortunately the centre of gravity is very high on this robot so it's ability to climb over things and deal with any rough terrain is pretty bad at the moment. I will try to fix that and the general messy wires situation once I have the power issues worked out.

I am also hoping to add some LED's and perhaps use the shift register, which came with my beginner kit, to do this. However it's workings are still confusing to me.

So there it is, my first robot. Still a work in progress but it's getting there.

 

First Bot 1.1 - Added a new project picture and video. The robot now has 12 AA batteries and the sensor and boards have been repositioned.

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Here's a guide on batteries I wrote up:

http://letsmakerobots.com/node/28427

I have basicly the same build for my bot. It seems to be a common first time build. only on mine I built the whole frame work and used the tamya tank tread kit. I have a ping sensor and a home made h bridge. I tried a 9v battery at first and had poor power then I built another layer and sandwiched a 7.4 rc car battery and it works great. It doesn't get slowed on the carpet and has great sustaining power. I am currently waiting to get a motor driver shield and an IR sensor and then I will do a post for mine.

 

A protoshield would really help you clean this up. I saw you mentioned working on "the messy wire situation". I've enjoyed the one from Adafruit, but there are tons. Sparkfun has their own as do many other places that sell Arduino shields.

http://www.adafruit.com/products/51

I wonder if you'd find it worked better turning on carpet if you had less track in contact with the floor causing less resistance when turning. 

For example, check out my review of Ro-Bot-X's Robot Builder's Shield. It really helped my clean up my build of Penny.

I tried removing one of the three axles so I would have less track in contact with the carpet. I think it turned a little better but it was still struggling. Also with only two sets of wheels on the bottom it rocked back and forward a little too much. I'm only giving the motors 4.8V from 4 AA batteries at the moment and they are rated up to 9V so I will wait and see how they go when I upgrade to 6 AA's.

Also thanks for the suggestion on the proto shield, that would certainly help keep the robot tidy and keep all the weight over the centre. I need to have a proper read through that review but the Ro-Bot-X's one looks pretty neat since it already has the motor driving stuff all there.

 

I'm pretty interested in trying out Ro-Bot-X's shields also. They look pretty interesting and useful.

They are good boards. I'm itching for an excuse to try out his new Robot Builder's Arduino, which has all the capabilities of the Robot Builder's Shield with an Arduino built right in.

I confirm. A good compromise is to have 2 differents power sources. One for the motors and one for Arduino. Usually I use 4x1.2V or 5x1.2V for servos or the power required for gear motors (es. 6V or 12V). For Arduino, I use a 9V battery.

On my bots I usually have two power sources, one for the motors; usually a 6x1.2V NiMh-pack and a 9V or something else that supplies above 7.3 volts connected to a LM7805 voltage regulator, the Arduino comes with a builtin one though, so I guess you could use that instead.