DETECTING FOR THE DEAF OR HARD OF HEARING
Quite a few years ago when I had a retail shop in South Ockendon there were these three blokes who would call in from time to time. They were all completely deaf and totally hooked on metal detecting. So how did they do it.
They all used a Whites detector model no 66TR. This detector had a huge control box about as big as a shoebox with a handle on top. Inside was about 14 AA batteries, circuit board, a big speaker and a lot of empty space. They would use these detectors with the volume set full up ( these were very loud detectors ). Although they could not hear a thing the detector vibrated like mad and they could feel the vibration through the handle.
There are two ways to approach this problem as far as I can see.
Visual: By the use of a small LED and a handful of parts.
You will need a light emitting diode ( LED ), one resistor and a jack plug. If you can see visually the jack socket on your detector while you are detecting this is all you will need. If you can not see your jack socket you will also need a small piece of two core cable, so that the LED can be put somewhere in your line if vision.
There must now be about a million different LEDS available. The one we use here is the same one that we use with our probe boards and is described as 5mm superbright orange .But there are lots of LEDS about and you can use most of them. If like me you can describe yourself as a saver rather than a spender you could use the jack plug and lead from an old pair of broken headphones. And there are LEDS being thrown away in all sorts of electrical equipment, but modern LEDS are very bright and efficient . If you look at the inside of the jack plug you will see that there are three connections ( it has to be a stereo jack plug by the way ). One connection to the long part of the plug, One to a small section near the end of the plug, and one to the very tip. You will almost certainly need to connect the LED via the resistor ( about 100 ohm ) across the two connections that go to the tip of the plug you will have to experiment a bit to get the LED connected the correct way around. The LEDS are like a one way street, the current will flow just one way through the device and depending on how your detector is wired you will have to experiment to find the correct polarity.
Carefully bend flat unused tags and solder LED and resistor. Then after you have tested that it works mould the whole thing in Blue Tack or other similar material to secure and waterproof it.
Two finished versions of the same idea. If you can see your jack socket while you are detecting you can use the one on the left. If you can't see your jack socket use the idea on the right then you can put the LED were it suits your detector.
The LED : The one shown here is described as above as a 5mm superbright orange and should cost very little, but don't get hung up on getting exactly the same one. Something similar will do.
The Resistor: This depends on your detector, the LED and on how bright or dim you want it to shine. The resistor here is 100 ohm .25 watt carbon film. Resistors cost virtually nothing so you can experiment a bit here. You may not need a resistor at all, but if you run the LED too bright it will waste your batteries and could burn out.
Vibration: Using a small vibration motor as used in mobile phones and pagers.
These small vibration motors can be purchased for a few pounds. Do a Google search "vibration motor" to find a supplier of these. Most detectors do not put out enough current to run these motors so you will have to construct the simple one transistor amplifier circuit as described here ===== I am still working this out.
# = @ put "metal detectors" for the subject