Circuit Lake

Electronic Project and Circuit Collection

Meeting Minder

03/23/2010 Category: AVR, Digital, Microcontroller, Project, Timer, Tools

The MeetingMinder is time reminder for public speaker that give a warning when their speaking time will end. The project is built as indication light tower that has red, green and yellow 360-degree wraparound lights, mounted to a base which houses a large two-digit seven-segment display and the control circuitry. The tower colors indicate “talk” (green), “wrap up” (yellow), and “stop” (red). Also, two colors in combination let the user know that the tower is in time setting mode as opposed to time keeping mode. (Red and Yellow indicate the user can program the “wrapup” time, while Red and Green indicate the user can program the “talk” time.) The display counts down minutes, up to 99, for each phase, until the last minute, when it counts down in seconds. The user can pause or reset the time at any time either through the base or through an infrared remote control. When paused, the tower light flashes and the timer stops counting down.

Public Speaker Timer project

The remote control consist of two buttons that work separately or together, depending on the mode the device is currently in. For example, if the user is talking and the MeetingMinder is in “talk” mode (the green tower light on), and the speaker wishes to pause the countdown while answering a question, pressing either button will pause the unit and cause the tower to flash. If the user presses the UP button, the count resumes; if the user pressed the DOWN key, the countdown stops and the red light comes on, said Jeffrey Bosch, the project designer.

The time reminder hardware is based on the Atmel AVR microcontrollers: a AT90S2313 in the base (see Figure 1), and a Tiny12V in the simple, two-button remote. To keep things simple, communication is done through the built-in UART on the base unit’s AVR over an infrared carrier of 38KHz. The display consists of a dual seven-segment .8″ display. The infrared receiver is a Panasonic PNAX receiver/decoder. An enhanced design will run from a single-cell NiCad using of the sleep mode to conserve power. The AVR in the enhanced version will also handle charging the battery.