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Revised 02/23/2002
In the unit I built, I used IC sockets for all the 8 pin dip IC's. I would suggest you do also!
I had considered using 4000 series IC's in the timing circuits but decided against it. Too many unexperienced hobbiests have problems with C-Mos. C-Mos would result in a slightly lower total current, but most of the current draw is from the coil, not the IC's.
I used good quality parts, you should also! D1 and D2 are high speed diodes. Suggest you use them! As to IC1, the REG-1117A. Well Texas Instruments sent me Free samples, Because I'm such a wonderful person! "What a crock of S--t". Need help getting any parts, E-mail me!
Carefully assembly and take care to do good soldering. Than, Recheck board for any shorts!
1) Only insert IC2 into it's socket, leave out the rest of the 8 pin IC's for now. Now Connect up your 12 volt battery to the board and connect a voltmeter negative lead to the 0 volt outside trace on the PCB.
2) Now touch the positive meter lead to the negative of the battery....and it should read aproximately -9.75 Volts!
3) Now touch the positive lead to the +5 volt and than to the -5 volt rails. Both should be correct polarity and within .1 volts of ideal.
If all is correct, disconnect battery and insert the rest of the IC's! And redo steps 1, 2 and 3! ALL Readings should be the same as before! IF NOT, YOU HAVE A PROBLEM!
Mechanical: As to a case and handle case: The case to hold the circuit board, battery, meter, speaker, controls and switch can be metal or plastic! totally your choice. The Coil must be mounted on a rigid, non-metalic plate and use a plastic handle and nylon bolts for assembly at the coil. 3/4 inch PVC pipe works good. Also, keep the cable running between the coil and the circuit board out of the magnetic field of the coil. Most people have seen pictures of metal detectors. Theirfore I'm leaving the actual design of the mechanics to each person. However, If you need help, you can contact me for suggestions.
Single Coil Instructions
Only insert R15, Not R16! Connect Only L1 to the board! Total current draw from the battery will be about 100 Ma. depending on your particular coil.
Dual Coil Instructions
Only Insert R16, Not R15! Connect both coils to the board! Total current draw will be about 150 Ma. depending on your particular coils.
SETUP for Circuit
IMPORTANT: GET ALL METAL OBJECTS AWAY FROM THE COILS AND EVEN THE WIRES GOING TO THEM! You Will probably want these wires to be shielded.
Once the circuit is operational, adjust VR1 for about 1 volt on pin 6 of IC9 at the test point.
Than set VR2 for a slow beat (about 1 beat per second) in the Speaker and Zero the meter with VR4. (Changing VR1 again, Will affect both these adjustments)
Now bringing a metal object into the field of L1, you should hear an increase in beep rate!
Coil shape and size will greatly affect sensitivity. A rectangle spiral is probably the most sensitive, also the most difficult to make! ****Here's where the playing comes in!
PROBLEMS....You can always E-mail Me at: chemelec@hotmail.com Please put "Metal Detector" in the "SUBJECT LINE"