I made a frequency divider using 74HC4040, and the 12MHz crystal oscillator is connect to CP.
The problem is when I put my hand above the 4040 (but not touching it), and it makes whole circuit doesn't work!? :? When I put off my hand, everything resumes normal. :?
I made a frequency divider using 74HC4040, and the 12MHz crystal oscillator is connect to CP.
The problem is when I put my hand above the 4040 (but not touching it), and it makes whole circuit doesn't work!? :? When I put off my hand, everything resumes normal. :?
also, make sure you connect a resistor (between 1K and 30K should be good) between the clock and the input (VCC or GND) which does NOT make the clock operate, that way, the only way for the clock to work is to supply a current to it higher than that determined by (input voltage) / (chosen resistor in ohms).
No problem if I touch the case of crystal oscillator. The problem is when I touch or place my finger close to 74HC4040 (even 4 inch away from 4040). :cry:
No problem if I touch the case of crystal oscillator. The problem is when I touch or place my finger close to 74HC4040 (even 4 inch away from 4040). :cry:
Pin 11 (master reset) needs to be connected to ground. If you haven't done that, that's probably your problem. When you touch the can on the oscillator, your body is referenced to circuit ground. When you are not touching the oscillator can, your body is floating, and is probably picking up power line (mains) radiation and re-radiating it to the floating reset pin.
All unused inputs on CMOS ICs need to be connected to one of the supply rails - whichever is appropriate.
Have you grounded all of the appropriate inputs? Input values can float if not properly grounded...which brings me to a somewhat related story:
Messing around on my RadioShack Learning Lab (great proto setup), I was doing a simple 4017 sequential LED flasher. While I was running it, the CLK line became unhooked from the 555 output. By touching/getting close to the wire, the LEDs would advance several counts.
Just a good interference story.
Moral: Ground stuff correctly and there won't be a problem.
I hate to repeat myself, but did you try Nigel's suggestion of grounding the oscillator can? (It may already be connected to the GND pin, but you should try it anyway).
BTW, what is that component (upper left) labeled R2 L - 47uF? You have managed to label one component as a resistor and/or an inductor and/or a capacitor. :?: :?:
Hi,
Wild guesses. You are sure; that the oscillator is connected correctly, using the right pins? That the output from the Oscollator is a proper logic signal and doesn't need a pullup or something? There is no control input on the oscillator that is floating?
A behaviour like this indicates one or more floating inputs/terminals. You have checked that all the chips are supplied with 5V. No floating GND or Vcc pins?
Have you looked at the oscillator output with a scope?
And last, have you checked the connection between the oscillator and the 4040? Ohmed from pin to pin? An 'air' connection here could function like described.