I am using DC circuit.
The result need to be start with 4 (4>3>2>1>0>9>8>7>6>5>4) and show by a 7-seg. LED. and down count for each second. No switches allowed
i know i need to use a:
74LS47 as 7 seg. decoder,
74LS190 as decade down counter and
NE555N as timer.
and my lecturer just give me a hints:
T=5RC (time equal to 5 times of resistance and capacitance)
so I'm planning to use a R10kΩ and 0.1uF cap to delay for 0100 starting.(74LS190 start at 9, I need T=5((9>8>7>6>5>4)) for starting the counting at 4. So, 5=5RC , 5=5(10kΩ)(0.1uF))
i am not going to let you tell me the whole construction of the circuit.
what i want to know is:
1. what is the truth table of 74LS190 when down counting?
2. how the (T=5RC) actually works? (does my plan works? If it does,)
2.1 where the RC circuit would be connected?
3. what is threshold and trigger at NE555N used to be?
4. is the pcb contain more component that i need to use?
5. is there some software to simulate a circuit? where should i download?
My english is so bad and reading datasheet is a nightmare. There should be more question but i don't know how to express. Sorry about that. If something confuse you or not enough evidence, ask me. And i would answer as detail as i can afford.
The result need to be start with 4 (4>3>2>1>0>9>8>7>6>5>4) and show by a 7-seg. LED. and down count for each second. No switches allowed
i know i need to use a:
74LS47 as 7 seg. decoder,
74LS190 as decade down counter and
NE555N as timer.
and my lecturer just give me a hints:
T=5RC (time equal to 5 times of resistance and capacitance)
so I'm planning to use a R10kΩ and 0.1uF cap to delay for 0100 starting.(74LS190 start at 9, I need T=5((9>8>7>6>5>4)) for starting the counting at 4. So, 5=5RC , 5=5(10kΩ)(0.1uF))
i am not going to let you tell me the whole construction of the circuit.
what i want to know is:
1. what is the truth table of 74LS190 when down counting?
2. how the (T=5RC) actually works? (does my plan works? If it does,)
2.1 where the RC circuit would be connected?
3. what is threshold and trigger at NE555N used to be?
4. is the pcb contain more component that i need to use?
5. is there some software to simulate a circuit? where should i download?
My english is so bad and reading datasheet is a nightmare. There should be more question but i don't know how to express. Sorry about that. If something confuse you or not enough evidence, ask me. And i would answer as detail as i can afford.
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