Rodo, a 2nd-Grade Science Fair Robot

Many, many years ago, our daughter Nicole said she wanted to do something for her school's Science Fair coming up in spring (2001). I had been wanting to make some kind of a little robot for a while, so I said "how about we make a robot"? She agreed immediately and enthusiastically. For her to get the most out of the project, I told her she had to do all the work she is capable of doing. Again, she agreed. (As we got closer to the big day, I had to do a little more than I wanted, but she did most everything except for drilling, soldering, and a few critical things.) Rodo's life began!

Rodo is based on FirstBot, a simple little robot made with CDs, model R/C servos, and a microcontroller. Last I checked, the webpage for FirstBot is no longer there. But it was available long enough to inspire Rodo!

When we decided on making a robot, Nicole wanted it to be like R2D2. I said there is no way we will have enough time to make anything like R2D2. It won't even be an R1D1. This little guy will be more like an R0D0 (R Zero D Zero). So we started calling it R0D0 --> RODO --> Rodo!

This Instructables is more of an overview than a step-by-step, intended to document Rodo so he can live forever!

4 unwanted CDs

3 R/C servos

Microcontroller (we used a Basic Stamp 2)

SP0256 speech synthesizer (and associated components)

2 solderless breadboards, 1 for the microcontroller and 1 for the speech synthesizer.

Stud Sensor

screws, nuts, bolts, spacers, etc.

2 wheels

1 Caster wheel

Small speaker

Audio amplifier

9 V battery and connector

4-AA battery holder and batteries

small toggle switch

Rodo's basic construction uses several CDs mounted together with threaded standoffs. The idea was to stack up the CDs and use each to mount things (batteries, motors, etc.) We realized early on that the CDs were not very stiff, so the bottom CD was replaced with a platter from an old 5 1/4" hard drive I have been saving (I knew I was saving it for something!). It is much stiffer than a CD, providing a very solid base for everything else to mount to.

Rodo's drive motors, tail wheel, and On/Off switch are mounted on the bottom of the bottom disk. The batteries are mounted on top of this disk. The next disk up in the stack is the brain disk. It has Rodo's brain and the stud sensor. We call the next board up the servo board because it mounts the servo which allows Rodo's head to turn. And of course the top CD is the head.

This is the base disk. The motors used for the drive wheels (mounted on the bottom) are modified R/C model servos. I've been flying model sailplanes for quite a while so I had extra servos I could sacrifice for Rodo. The modification allowed the servos to spin continuously. An unmodified servo can only move to certain positions. I debated for quite a while on how to mount the servos to the disk. I considered making a bracket and bolting them on, but time was running short (isn't it always!?) so we used servo mounting tape. It is a double-sided foam tape and quite strong. The wheels are from one of Nicole's K'nex sets. Servo control horns were screwed to the wheels and then the control horn/wheel assembly was screwed onto the servo. Also mounted on the bottom is a caster wheel we found at a surplus electronics store. The batteries were mounted on top of this disk. One battery provides power for the motors and the others power Rodo's brain. Rodo is powered-up when the switch on this battery disk is switched On.

The next disk up in the stack is what we call the Brain Disk. It houses Rodo's brain and the stud sensor used to detect objects. The model of stud sensor used is a "Stud Seeker". It was the smallest stud sensor we could find. Normally, a stud sensor is used to detect wooden studs in a wall. You place it on a wall, turn it on and slide it until a stud is detected behind the wall. But if you turn it on with nothing in front of it, it will detect an object that comes within a few inches of its "antenna". I soldered a wire from the the stud sensor and looped it around the front of Rodo, providing optimal object detection. It is the green wire seen in some of the photos.

A detected object is indicated by lights on the stud sensor. For Rodo, the wire that usually connects to the light was reconnected to an input to his brain so he will know when something is in front of him. I couldn't come up with an elegant (and quick) way to mount the stud sensor to the CD, so servo tape was again used. (That stuff is almost as useful as duct tape!)

Rodo's "brain" is called a microcontroller. The microcontroller used in Rodo is a Parallax BASIC Stamp BS2. The software and documentation are free downloads. We decided (OK, I decided :) ) on the Stamp because the software is easy to write and it's quick and easy to download to the Stamp. The Stamp is programmed in a simplified version of BASIC; Parallax calls it PBASIC. The software is downloaded using a serial cable and the Parallax software. The program and variables are stored in EEPROM in the Stamp which allows instant re-programming (and the program is not lost when power is removed). So you can make a change, download it to the Stamp, and repeat continuously (and quickly!). This proved very valuable when we were trying to get Rodo to say things correctly.

Why not use an Arduino? They did not yet exist back then! Remember, this was in 2001. The first Arduino was born in 2005. Up to this time I had been playing with PICs, but I thought the Stamp would be better for Rodo and this science fair project.

The disk above the brain disk is used to cover his brain and to mount his head servo on. We did not use servo mounting tape to mount the servo to this CD. There are four screws on the bottom of the servo which hold it together. We removed the screws, drilled four holes in the CD to match-up with the holes in the servo case, and then put the servo back together with the CD mounted to the bottom of the servo. The servo was not modified as the drive motor servos were. We did not want the head to spin around in circles; we just needed it to move to certain positions. This is the normal operation for a servo. Right next to the servo is the speaker through which Rodo speaks. We did use servo mounting tape to attach the speaker to this CD.

And last, but certainly not least, Rodo's head disk sits on top of the head servo. It was mounted the same way the wheels were mounted to their servos: attach a control horn to the CD using screws, and then screw the assembly to the servo. The speech processor, with an audio amplifier, is mounted on the top of Rodo's head disk. The entire board on Rodo's head is just for speech (it took quite a while to get all those little wires and parts stuck in the right holes). And, yes, the board is attached to the disk with servo tape.

We wanted some kind of a dome for the head, but after much searching we could not find anything the right size/shape. Then Nicole received a gift which was a ball-shaped game. The packaging around this ball was two plastic half spheres which were just the right size! (Lesson learned: you should never throw anything away; you may need it someday for your robot!)

The clear plastic dome covers Rodo's head. It gives Rodo a cool look because you can see the electronic components in his head (and the dome keeps curious fingers out). Nicole had a couple googly eyes, so she stuck them on the front of the dome. They are a bit small, but it was all we had.

When we first started on Rodo, I was thinking to have him make beep and boop sounds, like R2D2. My daughter wanted him to speak. I didn't think we would have time for that; beeping is easier and quicker. So, we had a vote. Speaking won. (me: beep, Nicole: speak, wife: speak) I had a speech IC I was playing with, so into Rodo it went.

Attached to this Step are the data sheets for the amp and speech processor. Also attached are .wav files of everything Rodo can say. Please listen to these; we spent a lot of time on them. :)

The image above is a list of Allophones. Allophones are sounds. String them together and you can create speech. If we had more time we prolly could have improved some of what Rodo says, but we did have a deadline.

There are 2 files attached to this Step. pseudoCode.txt is simplified pseudocode of the actual software. This is what Nicole presented during the Science Fair. The actual Stamp software is attached (rodo.txt). I had to change the extension from .bs2 to .txt so I could attach it, but it is readable as a text file.

So exactly what does Rodo do? When you first turn Rodo on, he says, “Where am I?”  He looks to the left, then right, then straight ahead. Then he says, “I think I am at Pinecrest School”, and then "Hello, my name is R0D0.  You can call me Rodo”.  He then begins rolling forward.  When the stud sensor detects something, Rodo stops and says one of three randomly selected phrases: “Oops”, “Object Detected”, or “Oh No”.  He then backs up a random distance, turns his head left or right (randomly selected) then rolls in the direction he looked.  That was pretty much it.

Sorry for the poor quality of the images. They were taken with a cheap 35 mm camera and then scanned, way back in 2001.