How I Made a Robot- D.S. (detailed Step-by-step)

This is a follow up of my previous instructables . Please comment on that page if you like my work.

Being a robot hobbyist, after seeing the Robot Contest up on instructables ,I decided to build one new bot. I named this bot D.S after the name of one of my favourite teachers at university - Debapriyo Syam.

Here is a video

This can be used as a robotics platform for beginners. When I was about to build the bot, honestly I had no idea what was I going to make. Initially I made a base like first picture. Oh well,my main ingredients were,

1. Hard cardboard
2. Hot glue
3. Strong papercraft glue
4. 3X Standard Servos
5. 4X mini servos
6. An Arduino board (You'll know why I am not mentioning the board name here)
7. Battery
8. 2X BO motors
9. 1X castor wheel
10. 3X Sonar sensors
11. wheels for BO motors
12. 3 Digit Voltage Readout module

So lets start.........

Step 1: Making the Base..

Through this instructables you'll see how I tried to build a successful bot and faced many problems and solved them in my own way. I request you to read this 'ible completely and then decide how are you going to build it.

As I have told I wasn't sure what was I going to make. So I started with two Bo motors ,two wheels and some cardboard. You can see my initial base design. later I discarded that and made myself a new one, You can see the details in the pictures..Initially I was going to use the wheels made for 6mm center shaft DC motors as those LOOK GOOD,but somehow the red wheels felt more stable on the BO motors. So I used them.

And oh,I used a Castor Wheel at the base to balance the robot.

Step 2: Arms.........

Each of the arms are made from three servos. One Hitec HS311 for the shoulder, two Vigor miniature servos for the gripper and the the elbow. All of the parts other than the servos are made from hard cardboard. I used saw to cut the cardboard pieces.. I used some double sided tape and some strong glue to fix the pieces together. Check the pics....

Step 3: Adding the Microcontroller Board...

First I added the Arduino Mega2560 Board to the base with Nylon screws and I put the mini breadboard in the base...Pics for you..
I used the breadboard as it gives the chance for easy connection.

At first I fixed the board in vertical position but later found out that it will hinder the movement of the head portion. So I changed it to horizontal position..

Step 4: Servo Power and Battery

For the battery I used a 2S li-po. It is the first Li-po I am using.

These Lipos dont have over-drain protection built in,so I built myself one from a spare Attiny, a 7805 regulator and a Power MOSFET. The protector takes the reading through a voltage divider and measures through it's analog inputs. It the voltage reaches below 3.3 volt per cell,it fires a buzzer,flashes a LED and cuts off the MOSFET resulting in disconnecting the load. refer to above pictures.

Then for added security I added a 10A Fuse to the battery power out cable. Also I added a DC jack to the battery. As my robot wont need current more than 10A, I think this modification is safe. 

If I power the servos straight from the battery ,i.e 8.4 V (max) then they are going to get fried. So I used 7805 ,7806 regulators on the breadboard to power the servos. Since each regulator gives only 1A current,I added 5 of them. If you have a BEC it might help..

Step 5: Head

I added another HS 311 Servo for the head. 

I built the head from cardboard. it's a normal cardboard box with a sonar in front and a Servo horn at the bottom.

NOW, there was a big problem.

To test the thing,I tried to connect the board to the computer,but the cable was damaged. So without proper cable I used another Arduino board, that is the Arduino UNO equivalent board. It worked fine....

Step 6: Voltage Readout...

I wanted to be sure than my over drain works perfectly. So I fixed a 3digit voltage readout in front of the bot. connections were pretty simple here. The readout has three wires, one Power,One Ground and other one for the Voltage to be measured.

First I fixed the readout in upside down manner, later again took it off and fixed again with hot glue...:p

Mistakes ! Mistakes !

I took two sonar sensor and fixed them on the arms of the bot. I have lot of jumpers,so I used them here..

Step 7: Motor Controller Circuitry and Other Connections

A L293D motor driver is used here. the connections are as follows-

Arduino pin          used as 
2                             Right arm Sonar triggerpin
3                             L293D enable pin
4                             Right arm Sonar echoPin
5                             Right shoulder servo
6                             Head Servo
7                             Left Arm Sonar EchoPin
8                             Left arm Sonar trigPin
9                             Left elbow servo
10                           Right elbow servo
11                           left shoulder servo
12                           Head sonar echoPin
13                           Head Sonar TrigPin
A0                           NA
A1                           NA
A2                           L293D
A3                           L293D
A4                           L293D
A5                           L293D

Step 8: Covering It Up..

Oh, that IS a mess of wires. How to hide it? I though a simple cardboard will be good. But it didn't turn out as expected..So changed my plan and let the wires show themselves...

At the backside I covered it up with a cardboard and made a battery holder...

Step 9: Finishing Touch..

Last but not the least, in fact most crucial part -programming.

Since this can be used as a platform to teach and learn robotics, this is upto you how to program this. Here I am uploading the obstacle avoider routine I have used in the video...

Hope you liked this. Thanks a lot for viewing this. I will LOVE to hear from you guys about your opinions.

Here is D.S posing with my scooter....trying to ride it ,but in a wrong way.....:D ....Have fun !!!