I've connect 7447 decoder and 74193 counter as shown in the picture but I have not used 555 timer yet.
Is there any way to test the circuit before using 555 ?
I've connected the pins (up and down) of the counter to the positive terminal, and then disconnected them several times. ( I just wanted to do the function of 555 manually ). but the display did not count up… why ?? I want to test the circuit before putting 555 ?
one more thing, what are the pins A,B,C and D of the counter ? why do we connect them to the ground ?
and also what Bo,Co and load are?
this is the datasheet of the counter :
http://www.ti.com/lit/ds/symlink/sn74ls193.pdf
Best Answer
Pins A, B, C, and D are inputs. If you want to load the counter with a particular value, you set these pins appropriately, then take the "Load" input low briefly. If you are not using this function, the pins can be left unconnected.
The "CLR" input must be held LOW for the counter to work, and pulsed high to clear the counter.
Bipolar TTL (74LSxxx) inputs appear High when not connected, but when used with switched, it is good practice to pull them high with a 4.7K (or so) resistor to +5 volts, and use the switch to pull the input to ground for a Low input.
With CMOS parts (anything with a "C" in the middle of the part number), unused inputs must always be connected to either +5 or ground, as needed to make the part work as desired. Switched inputs can be connected either as above, or with a resistor to ground, and switch to +5V.
The UP and DOWN inputs must be held high when inactive, and pulsed low to increment or decrement the counter.