help!!isolating circuits (on same psu) from each other????

loss1234

OK. this is bad.

I have a cd4040/cd40106 vactrol based sequencer running off of 9v on one breadboard. then on another breadboard i have another cd40106 circuit running , we will call it tonemaker-(its a little noisemaker, very cool, found here: http://experimentalistsanonymous.com/board/topic-382.html

Anyway, they are both being powered if the same 9v battery, since i am low on batteries. and WITHOUT EVEN HOOKING UP THE SEQUENCER TO THE 2nd BREADBOARD, i start hearing my tonemaker playing a sequence of notes!!

as i speed up the sequencer (which isnt hooked up to anything, no speaker, no output, except its hooked up to the same battery as the tonemaker on the other breadboard) i hear my tonemakers sound get faster and faster!!!

1. what is going on?
2. how can i fix it-with one psu?
regulators? caps? what do i need to do? this also happened to me with one other thing i was testing.

i mean when i am building stuff i like to be able to power things off of one battery.

is it because the battery line sends the audio from the other board? or is it far more complicated? there has to be some kind of filter i could make.

IS CMOS MORE PRONE TO THIS? seems so.

thanks alot.

this is ruining my day.

blue hell · Posted: Fri Sep 28, 2007 5:42 am Post subject:

Try putting a 100 uF .. 470 uF cap over the battery.

Batteries can have a fairly large internal resistance especially when they go empty or when it's cold. What happens is that when a circuit draws current from it the voltage will drop (same as what happens with a flashlight on an older battery, light goes on bright and dims quickly). The varying voltage can affect the other circuit (or the same as well, when it's really bad).

The large capacitor will smooth out this effect for fast current pulses. Be sure to have the + and - OK and the electrolytic cap will need a working voltage of at least 10 Volt for a 9 V battery.

loss1234 · Posted: Fri Sep 28, 2007 5:57 am Post subject: thank u

so put the cap between + and - or between + and voltage in on my circuit??

thanks

blue hell · Posted: Fri Sep 28, 2007 5:59 am Post subject:

Between the + and - of the battery.

Rykhaard · Joined: Sep 02, 2007 Posts: 1290 Location: Canada

mosc · Posted: Fri Sep 28, 2007 8:30 am Post subject:

Make sure you have separate wires (+ and gnd) connecting your sequencer and tone generator to the battery.

Put noise suppressor caps across the + and gnd connections on every IC. .01 mf is a good size to start with. Put them as close to the IC as possible.

You are probably going to appreciate a regulated power supply at this point. It can help to run the sequencer on it's own power supply separate from the tone generator.