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Velleman sound-to-light kit

A Velleman sound-to-light kit (Radio Shack MK103) is a small circuit board powered by a 9v battery which lights LED bulbs when an audio signal is received by the microphone.

I would like to connect this board directly to the headphone (output) jack of my audio device (metal detector), thereby bypassing the microphone input. This would allow visual operation of the detector without the use of headphones. When an object is detected it would illuminate an LED as opposed to sending an audio signal.

Is it possible to de-solder the microphone on the circuit board and solder in a 3.5mm male connector which would plug directly into the audio output device?

I have never worked on a circuit board before and I have ZERO knowledge of electronics, but the kit is only $8 - so I think it's worth a try - if the electronic wizardry is correct, that is.

Thanks in advance for any help!
-Bruce

Yes you can leave the mic off and solder in a 3.5mm male connector. Or you can take it one step further and integrate the kit directly into the metal detector soldering a set of wires from the mic of the kit to the back of the headphone jack on the detector. Then you can have both the visual and audio signals.

Its been a while since i messed with a metal detector. Even then it was a pretty cheap one so correct me if i'm wrong. Doesn't the detector constantly generate an audio signal that only intensifies when it comes across metal? Maybe the better detectors are silent till they detect something. Also, isn't the sound intensity different based on the size of the object? Problem with the sound and light kit is it's more designed to react to a beat or clapping your hands. It may not work as well as you would like to indicate when a metal object has been found and you could pass over some smaller items because the lights don't react enough. Just something you'll have to play around with i guess.
Inspector-Gadget (author)  mpilchfamily5 years ago
Thanks for the reply! This is a big help.

Yes, the detector can produce a constant audio tone, but the threshold can be filtered to reduce the continuous noise for silent operation. The sound-to-light kit would help by allowing me to detect without the use of audio tones - a great benefit for the hearing impaired.

The Velleman kit also has a potentiometer (?) which, I believe, also filters the audio input, so the light would not be blinking endlessly. As far as the separate tones generated - I don't know how it would handle those.

My detector cost is around $600, so I would likely not be too invasive to the circuitry, but simply plugging it into the headphone jack may be worth a try.

Thanks for your help and if I try the project I'll give everyone an update. This could help out anyone who is hearing impaired with an audio detector, or someone who likes to treasure hunt silently.

Take care,
-Bruce
Be sure to make a good instructable about it. Good Luck!