Hi, I am coaching a couple of high school students for Robofest (Lawrence Technological University's open robotics competition)...they want their Vex robot to make some sounds, and the RobotC language has a sound function and we can see the 'set motor to SPEAKER' option, and the RobotC guide talks about a vex piezo speaker, and we even have a PROGRAM that executes those functions, but we're not sure what HARDWARE to incorporate. The vex documentation refers to an "optional vex speaker", but we haven't been able to find a specific item linked to the VEX system or even generic how-to's for connecting low-voltage output devices to VEX. We can make some deductions based on forum discussions of more complex installations such as cameras, and I've accessed carnegie-mellon's instructional materials for making connectors.....

....but it seems this should be an awfully easy question for someone to answer, as all i've been able to gather from the web is that it's one of those "everyone knows" items.

Is the guide referring to a specific part that is related to the VEX robotics system, or a speaker made by the vex audio systems company....(I realize this isn't quite a programming question...but clearly others are aware of a source for a basic speaker...is it a part others had access to through FTC at some time?) We've searched all over this site & find only references TO speakers but only one direct reference to a specific part--an advanced speech-synthesis module that we'd be a bit hard-pressed to figure out how to wire up--again, this seems to be one of those things that "everyone knows".

Thanks for any clues or tips or links to sources on this topic....

Vanessa MacLaren-Wray
LTU Robofest coach
San Martin, CA

fyi FTC is no longer vex, it is tetrix

For the other newbies out there, here is one solution we found: at Radio Shack ask for part number 273-073A. This is a piezo transducer. It's OK in the VEX voltage range. It's a two-wire square-wave device. Connect the black wire to the black connection in motor port #1; connect the red wire to the PWM (pulse wave modulation, for the signal) connection in motor port #1. It's not very loud, but it does the job. It costs about $2 allows you to run the Sound With External Piezo Speaker sample programs (e.g., play the theme from "Mission Impossible") and then move on to write your own sound programs.

For help with making the actual connection, Carnegie-Mellon has some step-by-step help on putting together wires in their curriculum materials under "resources":

http://www.education.rec.ri.cmu.edu/rob ... /index.htm