Making ic 74190 starts at 60 to 00

[ChuChu_06]

I'm designing a count down timer using ic 74190 to starts at 60 sec to 00. I want to add similar to a debounce switch for my enable so that it will straight starts at 60 instead of 99 when it is activated along with the PL. I need some help with the debounce.

In addition, I also want to add 3 blinks before enable and a single cycle, then 3 blinks after reaching 00

 

[BradtheRad]

You can pre-load the inputs with any desired bit pattern via diode logic, and with the help of pull-up/down resistors. Select ohm values great enough so as not to interfere afterward with normal running (highs and lows).

 

[ChuChu_06]

You can pre-load the inputs with any desired bit pattern via diode logic, and with the help of pull-up/down resistors. Select ohm values great enough so as not to interfere afterward with normal running (highs and lows).

oh yeah it works, i added a nand gate to the enable so it will start once the "switch" is pressed. The question now is whether i can combine the PL to the enable so it can simultaneously enable and starts with the pre-set 60

edit: I just attached one of the input from the nand to the button and it works well, although it will got 99 after the first cycle(but that's ok cause i only need one cycle)

 

[KlausST]

Hi,

do an internet search for "simple debounce circuit" ... for ideas. Best if the circuit comes along with a description about the working principle.

Starting form 60 is a different problem. It is called "preset". The IC datasheet gives the informations how to do so. You need to reasd it first, then try, then - if any problem arises - tell us what you did, what you expected, what happenend instead.

AND: for a real circuit -- you need to add power supply decoupling capacitors.

Klaus