i have just gone out and got a cable tester from maplins, works like an inductive amplifier, detecting a tone present in the cable. Im detecting tones from 500hz to 3000hz.
I want to take to audio speaker output of this tester and put it through some kind of filter, when a tone between 500hz and 3000hz is detected i want to light an led, the unit is powered by a pp3 battery.
I am thinking he wants to use a visual indicator instead of a tone. Maybe a simple comparator circuit would do the trick. Not sure why you would need a filter. If tone is present between 500Hz to 3KHz a comparator would detect that. Are there other frequencies present which you wish to filter out?
Sounds like the device is a cable tracer and not a tester. I don't know why you'd want a visual indication because the loudness of the warble tells you how close you are to the cable.
I am thinking he wants to use a visual indicator instead of a tone. Maybe a simple comparator circuit would do the trick. Not sure why you would need a filter. If tone is present between 500Hz to 3KHz a comparator would detect that. Are there other frequencies present which you wish to filter out?
your spot on there... 'probe' already has a speaker and led, when i put it against the audio cable im 'testing' i can hear the tones very faintly at 500hz it becomes clear at 1000hz, at 3000hz its purfect
anyway, i need to provide an output suitable for a device with 1.5v - 4.5v nominal voltage range and current 175mA, its a little motor. i had said led because i didn't want to complicate it too much but with the current being 175 mA i though i should provide this additional info.
ideally i was going remove the exsiting speaker and use audio output from the probe on this additional circuit. The output would only be activated if a tone between 500hz and 3000hz was detected, hence filtering out anything below 500hz or above 3000hz, would also help get rid of any ac hiss and crackle!!