Clock Controller circuit


Posted on Feb 6, 2014

The Clock Controller was designed to be an exemplary of using `C` language to control timer0 interrupt, 7-segment LED and keypad scanning. It provides 1-bit sink current driving output, for driving a relay, opto-triac, say. Many projects requiring 7-segment display and keypad interfacing may get the idea from the Clock circuit and software. Fi


Clock Controller circuit
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gure 1 depicts a circuit diagram of the Clock Controller V1. 1. P10-P1. 7 drives 7-segment common anode LED with sink current. P3. 0-P3. 3 also drives a base pin of 4-PNP transistor, 2n2907 with sink current. As shown in the figure, the 2nd 2-digit LED that connected to P3. 2 and P3. 3 is rotated 180 degrees to the 1st 2-digit allowing the pt. segment to be used for 1 second blinking. P3. 0-P3. 3 also connects four momentary switchs while the other legs are tied to input port P3. 4. During display and key switch scanning, a logic `0` is shifted from P3. 0 to P3. 3 every 10ms, if there was a key pressed, P3. 4 then became low. P3. 7 is a 1-bit sink current driving, an example in the circuit uses a 2n2907 to drive a small electromechanical relay 5V, say. The program clock. c was written in ‘C ’ language and was complied by Micro-C Compiler from Dunfiled Development Systems. The memory model is TINY. The hex file of clock. c suitable for downloading by Easy-Downloader is clock. hex. I suggest to use a zero switch solid-state relay for driving heavy loads (>10A). Most solid state relays`s input can be drived with 3-30Vdc without any problems.




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