Hello all. I am relatively new to electronics as a hobby. I have been computer programmer and wanted to get into the electronics side of things.

For my first project I wanted to make a Binary Clock using 555 timers and 74LS290 Decade Counters. I have the 555 timer sending out a pulse with a period of as close to 1 second as I can muster (about 987 milliseconds), and I have the first counter and the second counter set up properly.

To give you a better idea of how I did it, I have the Q0 and Q4 (1001 or 9) pins of the first counter going through a 2-input AND gate and that pulse is used to trigger the second decade counter. This one works fine.

Now from the second decade counter to the third to count a minute, I have to use pins Q0 and Q2 (0101 or 5) through a 2-input AND gate so when the final pulse of the first decade timer changes the second to 0110 (or 6) the falling edge of the logic gate output will trigger the third decade timer. However...the problem is when second decade timer is going from 0011 to 0100 at one point (for a very brief instant) both Q0 and Q2 are true during the transition...so the third decade counter picks this up as a pulse, as does the reset pins of the second decade timer, so it resets ten seconds too early and the third decade timer increments ten seconds too early.

I am at a loss as to how to fix this issue...any suggestions? Thanks in advance =3.

 

Use a crystal and a divider IC, such as the 4060.

a 32.768kHz crystal divided by 2^15 can be done with the single IC.

If you are very comfy with programming, take a look at PIC microcontrollers (or AvR). But to learn the "glue logic", you are on the right track without uCs.

 

I will give that a shot. I wanted to learn about the lower level stuff first. I did order an Arduino from SparkFun to try to combine my knowledge of programming and my limited knowledge of electronics together.

 

You WILL need a comprehensive concept of basic electronics. Go through the e-book links along the top of the screen for that.

Tie uCs together with common circuits, and you end up being able to build 90's level "tech" as a hobby.

 

Another good site (minus the forum). Mr. Bowden also has a binary clock design using 74390's.

Bill Bowden's Hobby Circuits

 

All of his circuits use the 74HC390's...what is different about them? Are they high current versions of what I am using?

 

Nope, just another way to skin a cat.

 

Hi deusprogrammer,
I have actually built Bill Bowden's binary digital clock, and it worked first time it was powered up. I would recommend it to a newbie electronics guy.
Regards,
Mike