hey guys.
im a fresh student of engineering and quite having problems on circuits.
my project is to make a 59 seconds timer or 1 minute timer using 555, 74LS47 and 74LS190 .im going to dispplay the numbers using two 7 segments.

my problem is i dont kow to make it stop at 5 and then loop again.


please i need your help.

 

Monitor the output of the counter with a logic gates circuit. When its output reaches 59 the logic circuit will disable the 555 by driving its pin 4 low. The output of the logic circuit will feed a 2-input XNOR gate. The output of the XNOR gate will drive pin 4 of the 555. On the second input of the XNOR gate put a push button which will start the counting again when pressed.

 

please help me...

im all new to this kinds of stuff...

 

thinking...

its so hard for me but my professor told me it was easy..



he told me to use only 74LS47,74LS190 and 74LS08, plus the 555 timer...

 

Use Google to get data sheets for all those IC's - use "74ls47", etc as the search term.

 

Think AND gate, feeding a reset (or a preset number, same thing).

The number 5 is binary 101, which is not what you want. The binary number for six (110) would be where you reset.

You could use a diode gate (they work well with TTL) or a TTL gate (qty 2 7400 gates, quad NAND).

 

Hello friend,
I feel this can make you good

Just have a look at the image ...If u want i can give you the circuit too
I dont know how to attach a image so i have done with a word doc

 

But that doesn't match his part requirements.

The AND gate can pick up on the number I showed you (binary for 6), and feed into the reset pin.

The 74190 is a pretty cool chip too, since you can make it start from any number. Reset takes it to binary 0, but you can treat the preload inputs as another form of reset, and take it to any number you choose.