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Registered Member #190
Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567
I asked this a while ago. I need a circuit to run a 120 second clock on one limb. Every 120 seconds it will toggle between an on/off state. The second counter will start 90 seconds into the first counter and also run for 120 seconds and do the same. I may need to very the counting range.
I've looked at pre-built timing circuits, but nothing seems adequate so I will build one. Is it easier to go with a 555 type design and use decade counters, or should I use a microprocessor like an Arduino to run the cycles?
Registered Member #3900
Joined: Thu May 19 2011, 08:28PM
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Posts: 600
Microcontrollers can be very accurate when you count off increments of something like one second when using the 16 bit timer/counter and you use a high frequency accurate crystal. Beyond that, you can just do a code counter to count the number of seconds passed, then another to change the state of the pin after the desired increment. I'd chose that over some rc based timer any day.
Registered Member #190
Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567
I have the atmega328 running the program now. I'm thinking about adding a 3 digit counter to display the count-down. I can use the 328 to run the abcdefg segments and multiplex the three digits.
This is the lcd display I'm thinking of using:
Since it has the inputs for all three digits I figure I will have to use AND gates (or NOR if I'm using LOW to light the segment) on all segment inputs so I can control which digit I hit. I have seven digital outputs for the segments and I can use three more to control which segment I light. Does this sound reasonable?
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dual timing circuit
