I'm trying to modify a circuit where a tone detector is sending a signal to another device that will read this output as a simple Boolean signal. The problem is I want the tone detector to read the signal for like 15-20 seconds to eliminate the chance of it reading random noise interference. What would be the best way to implement this? Some type of setup with a capacitor storing the charge and then dissapating after a certain amount of time (maybe with a schmitt trigger, comparator, ?).
Kris.
The NE567 tone decoder can detect a tone buried in noise. You can connect an output filter capacitor to pin 1. This prevents false triggering, and dropouts; but it introduces output chatter. The chatter could be removed by a monostable, if required. Alternatively, the chatter can be eliminated by applying positive feedback between pins 8 and 1. See the datasheet for details:
Thanks Andrew.
-- Do you already have the tone detector implemented? if you do, does its output go high or low when it detects the tone its supposed to? What is the tone detector\'s output voltage? What kind of a load can it drive?
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