From: Old Lady
Subject: Help needed in designing a press-release button to switch on a logic+analog circuit and "explosion" in headphones!
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Date: Sat, 19 Oct 2002 08:56:02 GMT
I have a problem I can't solve without your help.
I need to power on a circuit in which there is a logic section powered
+5V and an analogic section powered +12-15V.
The circuit is battery powered, so it should be disconnected when not
I need to press a button (I don't know the exactly English name, but
is a button that you can press closing the circuit and when you
release it, it immediately open the circuit again) to power on the
circuit, which starts a digital counter and other few things. When the
counter reach the status 111, one cmos-AND port should switch off the
circuit and NO POWER should be drained from the battery, at least
until one press the button again switching on the circuit.
My English isn't so good, but I hope I'm understandable!
Another problem is that when I switch on the circuit manually (with a
classic on-off switch), I ear like an explosion in the headphones
connected to an LM386 in the analog part of the circuit. Any idea how
to avoid this? Should I separate the digital and analog grounds? How
to do this? I also tried to put a ceramic cap between +12V and GND but
Please, help me!!!