PROGRAMMABLE_TIMER_SEQUENCER

Published:2009/7/14 19:40:00 Author:May | From:SeekIC

The circuit diagram of this programmable sequencer could be applied in a number of timing uses. Prior to the start of each interval, an audible tone is generated, and a seven-segment LED display shows the interval number. Prior to the end of that inerval, the buzzer sounds again. IC1 is a 2240 timer/counter device that clocks up to 256 periods, the durations of which are determined by resistor R1 and capacitor C1. The 2240 has its RESET and TRIGGER pins (10 and 11) wired via a push switch S1.The timer is used to operate a memory chip, IC2. The first 8 addressed bits are used by the timer/counter to step through the 256 steps available for each program. The other 6 bits are selected by an external switch network S2 to S7 which permits up to 26 programs, each of 256 steps. The 27C64 has eight outputs, which was enough for a single-digit LED display plus a piezo buzzer.



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