It’s finally published! Make Magazine Vol.31 has my Automatic Ball Launcher on the cover and a full build article inside!
I wrote the article around the first of the year and after much editing and emailing we put together an awesome how-to with great pictures, diagrams and detailed instructions. The people at Make did a great job creating the illustrations and building a cover version and a standard version of the “Fetch-O-Matic” for the article. Big thanks to Make for the opportunity to share this project!
I designed this ball launcher with three things in mind. Mechanical simplicity, ease of operation and ease of acquiring parts. You can readily get all the parts needed to build this ball launcher from online sources and your local hardware store. It has minimal wiring and requires a medium skill level in carpentry, wiring and machine work. Most people that make and fix things in their garage or workshop should have most of the tools on hand to build it. The whole thing is self resetting and mechanically simple with only three moving parts. It operates on a cordless drill battery, a windshield wiper motor (worm gear reduction/high torque), some wire, and a micro switch.
You can download the PDF build templates and schematic here.
It can talk! After a long session at the workbench this past Sunday, I managed to build the mechanism and the circuit to make my robot box talk with Emic 2 supplying the speech! I used a random function in the Arduino code to get Emic 2 to speak random phrases. I’m still working on better code so I’ll wait until the final installment to post it here.
The sound to voltage circuit was explained last week and this week it all got mounted on a perfboard along side an LM386 amplifier circuit.
The motor with the bent wire worked perfectly to open the mouth, and gravity closes it when the voltage is no longer present.
I drew up a new schematic too…
Next week there will be two robots having a “random” conversation with each other. That should be fun! Enjoy the video and until then…
Last week I worked on getting familiar with the Emic2 text to speech module connected to and Arduino. This week I’m working on a way to get the mouth of my robot to move in sync with the words that Emic2 is saying. I realize that I could take advantage of the Arduino and write some code that would do just that, but I’d rather find a solution that takes advantage of the audio signal that Emic2 is generating. Since there is a rise and fall in sound signal amplitude, this could translate to a fluctuating voltage connected to a motor. By turning at variable speeds in proportion to the variable voltage of the audio signal, the motor could move a cam that opens and closes the mouth in sync with the words… sort of.
That’s what this circuit does in a sense. The signal enters the circuit through the two small transistors that serve as a switch and an amplifier. When a sound signal is present, the first transistor turns on and allows the second transistor to amplify the sound. This signal then goes to the gate of the MOSFET which in turn switches on and allows current flow across the drain and the source. This current flow can power a motor or servo to open and close the mouth on a robot. As you’ll see in the video, I managed to get a gear motor turning by inputting the sounds from the Emic2.
Next week I’ll tackle the code to generate random phrases. Still working on that one. Arrays? Switch/case? Time to learn more C.
I was fortunate enough to be a beta tester for the Emic2. I subsequently recieved a second production version of the module. Joe Grand of Grand Idea Studio did a great job designing this very elegant device. At 30mm x 32mm x 10mm and only 6 pins it can snuggle into a tiny space. When it’s connected to a micro controller chip it can give voice to virtually any device… after a bit of hardware hacking. 😉 Joe has a video up of a hack he did on his kid’s toy.
This little gem can be purchased from Parallax Electronics. It comes with a great data sheet that gets into the nuts and bolts of what this module can do.
My girlfriend Lisa came up with a creative way to use two of these modules. She had the vision, I’ll be engineering the project. In this first of three installments, I’ll introduce you to the Emic2 and reveal the “idea” we have. This is going to be FUN!
The iRobot Roomba is a great robotic device for hardware hackers and robot builders.
They can be found on Ebay for as little as $20 with and without batteries. The battery pack seems to be the main reason they get sold because most users just don’t want to bother replacing the battery, which costs about $45 on Ebay. Other items that cause problems are dirty wheel sensors, a siezed cleaning brush motor and an occasional broken drive belt. Most of these problems aren’t a concern to hardware hackers.
This little four-wheeled robot has been through several changes during it’s life. It started out with a wooden chassis, then aluminum in a couple configurations and now here it is in it’s fourth iteration built with Micro RAX. MicroRAX are made from extruded aluminum and come with fasteners and pre-cut joinery hardware which makes them ideal for robot prototyping. They assemble quickly and accurately and can be easily reconfigured as the design may require. Prototyping is about problem solving and adapting new designs and MicroRAX make this easy!
This bot uses four Roomba motors, a Roomba 400 series mainboard and a Seeduino MCU. The Seeduino sends a PWM signal to the Roomba mainboard H-bridge to control the motors. The pictures below show the four points of motor control on the mainboard PCB. The yellow wire controls forward motion, the grey wire controls reverse motion. There are two H-bridges designed to run two motors, but each H-bridge can easily power two motors at once.