(1)There is a major problem with the 7 segment LED counter (using 74LS90 TTL BCD counter IC & 74LS47 TTL seven segment display driver IC). I have built one but it start at 1 rather than 0. Then i tried building another same one and this time it start with '5' (i have tried building it again and again but it still start at '5'). I have tried to combine the two circuit and I am getting '51' (as the first circuit start with '1' & the second circuit start with '5') but i want it to start/begin at 00(zero). I have made some research on the 74LS90 TTL BCD counter IC, and found out that using pin 1&2 and 6&7 can reset the counter. But I have problem figuring out the connections. I am not even sure wether resetting it will give make it into 00(zero) or reset it to '51'. (everything was done on a brick board and tested on a 'logic trainer' using 5V).
(2)There is another funny thing about this counter. Every time I off the main power source, it will randomly show a number before turning off and if I turn it on too fast(right after I turn it off) it will begin with another number (lets say, normally it begins with '5', when turned off-on too fast it will start with '9'). Is there an explanation to this?
Is there anyone able to solve my problems especially problem (1)... hope to get a reply as soon as possible. Thanks.
(2)There is another funny thing about this counter. Every time I off the main power source, it will randomly show a number before turning off and if I turn it on too fast(right after I turn it off) it will begin with another number (lets say, normally it begins with '5', when turned off-on too fast it will start with '9'). Is there an explanation to this?
Is there anyone able to solve my problems especially problem (1)... hope to get a reply as soon as possible. Thanks.