555Timer, 7440 Counter, and 7475 Latch

[wrightdd]

Right now I have a 555 Timer set for 2ms. The pulse feeds into a 74HC40 binary counter. The signal then travels from the counter to a 74HC75 Latch and from there to LED's. The expected timing coming out of the counter is correct (they've been measured with an oscilloscope). However, the LED's are lighting up in half the time (literally). The not output of the latches are going through an inverter and a NAND gate and back into the clock (reset) of the latch. Any idea as to why the LED's are lighting up in half the time the pulses are coming out of the counter?

 

[MacGyverS2000]

This sounds like schoolwork...

Dan - Owner

http://www.Hi-TecDesigns.com

 

[wrightdd]

I am a student, but this is not for school, I'm actually co-oping for an engineering company. This is an issue in our circuitry and we can't figure out what the deal is.

 

[IRstuff]

What are you using to latch the latches?

TTFN

FAQ731-376

 

[wrightdd]

Sorry, I actually just figured out the issue. Turns out it was a lot simpler than I realized. I was measuring one entire cycle coming out of the counter: low to high back to low, whereas the latch was simply waiting for the signal to go from low to high, thus only being half a cycle and expaining why the LED's were coming on in half the time.

 

[itsmoked]

Yep yep.. Thanks for telling us about the solution. G'day!

Keith Cress
kcress -

http://www.flaminsystems.com