sequential circuit design

Jul 30, 2005 1 Replies

I am having trouble drawing up a state diagram or state table for a sequential circuit for something I am designing.



In = 1, Out = 0 In = 0, Out = 1 In = 0, Out = 0



I got this far, from refering back to a text book on logic and design: 1/0 0/1 0/0 A ---> B ---> C ---> D where each letter is a state which occurs because the previous input was what was needed....After this I am stuck. How are you suppose to map unwanted states, refer them all back to A cause the sequence isn't correct.



I was thinking using an edge triggered flip-flop, but then I got stuck....



I was also considering a SR latch, where the output is feedback to the reset line, but I needed some way to increase the propagation time, so that it doesn't reset in a few nano seconds and the solenoid has time to act.



I needed to pulse a solenoid to close a valve after a trigger had been activated, because the valve didn't have a spring return :( I could do it using a microcontroller, but if I could implement it with a sequential circuit it would be better....



You can do it easily with a 7555, like this: ( View with a fixed-pitch font like Courier New) Vcc--+---------+-------+---------+--------------+-------+ | | | | |K | | | | | [DIODE] [COIL] [10K] [10K] [Rt] | | | | | | +-----+-----+ +-------+ IN>--+-[0.1µF]-+-------|--O|TR Vcc | | | |_ | D +--O|D OUT|------G | | | S +---|TH GND | | | +-----+-----+ | [Ct] | | | | | GND>-------------------+---------+--------------+ _____ ___ ...___ IN |____________ ...__| |_____ ____ ____ OUT_____| |_______ ...______ ...___| | -->| |

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