xTimer V1.0

Published:2011/4/25 3:20:00 Author:Ecco | Keyword: Timer | From:SeekIC

Complete schematic is shown in Fig 2. The MCU is AT89C4051 with 11.0592MHz xtal. The MAX7219 needs only three signals, CLK, DIN and LOAD. These signals are software generated assembly code. You may learn how assembly code interface with c from the firmware. Since when power up, all port bits are logic high, so I chose the 7407, open collector to provide NPN O/C output. These output bits are suitable for opto-isolator driving. The sample output module is opto-triac, the MC3040. The input circuit is simple with current mode driving, say 15mA is enough for MC3040. The output triac having ZCS drives a 220V coil electromechanical relay. Since the relay contact provide NO and NC, so we can provide two function AC plugs, i.e., delay on for NO and delay off for NC contacts. The sample schematic shown in Fig 2. has the relay circuit that uses opto triac driving a NO/NC relay! So I must change the firmware to let the output turn on when start timer and turn off when time is over. To do such changing, it needs to modify the source code and recompile it. I thought why don't try with sdcc. The people can modify the source code and do-it-yourself.



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