Tek-Tips is the largest IT community on the Internet today!

Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!

  • Congratulations cowski on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

555Timer, 7440 Counter, and 7475 Latch

Status
Not open for further replies.

wrightdd

Aerospace
Joined
May 28, 2008
Messages
6
Location
US
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?
 
This sounds like schoolwork...

Dan - Owner
Footwell%20Animation%20Tiny.gif
 
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.
 
What are you using to latch the latches?

TTFN

FAQ731-376
 
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. :-P
 
Status
Not open for further replies.

Part and Inventory Search

Sponsor

Back
Top