I posted a video demo that explains everything.Why you need that bjt stage for?
I posted a video demo that explains everything.Why you need that bjt stage for?
OK, I tested it out and it seems to work pretty good (Video Uploading) so I'll post that here ASAP.Connect pin 4 to pin 8, and its perfect.
Hmmm I don't have a cap on pin one?To prevent power up pulse, you will need a 1 meg resistor and 1uF capacitor on pin 4,resistor to pin 8, cap to pin 1, this will hold pin 4 low for about a second.
nF or uF cap?
OK I made those changes and it still produces a pulse on power up?
Oops my bad.... I swapped it out for a 1uF cap and it still doing it?The capacitor is the wrong value, you have used a 100nana farad, you need a 1 micro farad, thats 10 times bigger.
I didn't have a 2uF cap the next size up I had was a 10uF, it still does it with a 10uF in there.Ok is the timer giving a pulse out on power up or the dtmf chip,?
Try increasing the capacitor to 2uf (microfarads)
Then you reducing the values of R to about 200K.I didn't have a 2uF cap the next size up I had was a 10uF, it still does it with a 10uF in there.
Its giving a pulse from the 555 timer on power up.
Just tried that, still does it??Then you reducing the values of R to about 200K.
Should 8 & 4 be connected directly?Impossible if pin 4 is held low the timer cant give a positive pulse out, think you have wired pin 4 up wrong.
Try shorting pin 4 to pin one, then power up, it should NOT give a pulse out