METAL DETECTOR

INSTRUCTION SHEET

 

Price - Stock No 290


Description

This kit will help locate pipes or other metal objects to a depth of 8 cm.  Whether fossicking or renovating, this kit is simple to use.




 

 

 

 

Construction

  1. Inspect the tracks for fine breaks and test the continuity of each track with an electronic circuit  tester or ohm-meter.
  2. Identify the resistors using a multimeter or the Resistor Colour Chart .
  3. Bend  the  legs of the resistors to match their respective holes and push them through from the plain side of the P.C.Board.  Solder in place - refer Soldering Technique   
  4. The 14 pin  IC  socket can be pushed carefully into place. Solder in place.
  5. Identify the capacitors - refer Capacitors
  6. The ceramic capacitors are not polarised.  Solder the ceramic capicitors in their respective positions.
  7. The 100uF electrolytic capacitor is polarised, identify the location and orientation and solder.
  8. Eight PCB pins can be pushed into the holes where the leads connect.  These can be soldered. 
  9. The transistor must be orientated correctly and soldered. 
  10. Figure 8 wire is enclosed for use when mounting the potentiometer, switch and earphone socket away from the PCB - these are only short lengths and the remainder is for connecting the coil (L1). 
  11. Using wire strippers, bare and tin the ends of the lengths of fig 8 wire - see refer Tinning wire.  
  12. Solder the battery snap, potentiometer, switch and earphone socket to their respective PCB pins.
  13. The enamelled copper wire needs to be wound onto a round former 140mm in diameter, 40 turns.
  14. Trim the remainder enamelled copper wire.  The ends of the coil must have the enamelling removed to allow soldering.  Use a sharp knife or fine sandpaper to remove the enamelling from about 5mm of both the ends of the coil.
  15. Shrink tube is provided to insulate the ends of the coil after soldering to the fig 8 wire.  Solder the connections and shrink the tube.  Connect the figure 8 wire to the PCB pins for the coil.
  16. Establish the correct orientation of the 4001 with the locating dot on the IC and on the diagrams.  Insert the IC into the socket with care.
  17. The Metal Locator is now complete and ready for testing.

Testing

  1. Connect a battery and plug in the earpiece. 
  2. Adjust the potentiometer until no noise is heard. 
  3. Pass the coil over a metal object, if the kit does not 'buzz' re-adjust the potentiometer. 
  4. Fine tune until maximim sensitivity is reached.

Trouble shooting

Troubleshooting  if necessary will involve careful checking of locations and polarity of components, the diodes and that the locating DOT on the 4001 is as the drawing shows. Re-solder all joints and check to make sure you have not  bridged across between any two adjacent component legs.

Technical notes

First we must understand what the IC 4001 is. Datasheet for the 4001. 

This kit works by setting up two oscilators.  One is adjusted by the 5K potentiometer, the second is influenced by the inductance value of the coil (L1). 

As the coil moves over a metal object the second oscillator changes its frequency.  The frequencies are added and when the frequency differs the difference is output to the earpiece.









 

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