Updated Mar 6 2006
A Kit of Parts is Available, Price depends on what you want. Not everyone wants everything. Parts Ordering Info, "Click Here"
IMPORTANT NOTES:
Substituting an LM317 for the REG1117A will work OK for a Bench Test, But it is "NOT A GOOD SUBSTITUTE" on the final project. It will cause instabilities as the battery voltage drops to 12 volts! This will result in poor control of the unit and require more on-going adjustments. The REG1117A is a LOW DROP OUT VOLTAGE REGULATOR. The LM317 has a possible 2.5 volt drop across it.A 1N4148 in place of the 1N4937 will also work for short term, but will probably fail later. It's Too low of a current rating. A 1N4005 will work, But at a Lower Efficiency. It is Too Slow.
Where I Recommend "Polyester Metalalized Film" Caps, "Mylar" Caps are also OK. However, "Cheap Disk types" of capacitors will result in Drift and Unstable results. Do Not Use Them.
Also Note: Some Manufacturers mark there caps in Nanofarads. .001 uf = 1 n (n = nanofarad) .01 uf = 10 n .1 uf = 100 n
Capacitor Voltages are not critical, as long as the cap voltage exceeds the actual voltage in the circuit. The 1 and 10ufd, 10 Volt Tantalum caps listed below are Minimum Voltage Ratings. Same goes for the Electrolytics.
PCB *** You Can Make your own, or order one from me!
R1 110 All resistors listed here are 1/4 watt, metal film types. R2 750 R3 47K R4 47K R5 5K1 R6 4K7 R7 3K3 or 1K8 R8 68K R9 1K5 R10 68K R11 150 R12 680 R13 150 R14 680 R15 1k5 ("J1" on the schematic) Use for Single coil design. Do not use R16 R16 470 ("J2" on the schematic) Use for Dual Coil design. Do not use R15 R17 470 R18 680 R19 10K R20 330 R21 820 R22 47K R23 220 R24 1K R25 1M5 R26 51K R27 51K R28 2K2 R29 2K2 R30 18K R31 8K2 or 220 ohms for Expanded Meter R32 470K R33 68K R34 1K2 for Expanded Meter.
VR1 25K Phier PT10V Trimpot (DC Offset for IC9) Vertical Adjust style. VR2 50K DC Offset for IC10 (Beep Null) VR3 1K Volume VR4 5K Meter Zero VR5 Optional Pulse Width Control (10K) This is "R5A" on the Schematic. VR6 Optional Dead Time Control (5K) This is "R7A" on the Schematic. VR7 Optional Recieve Time Control (5K) This is "R9A" on the Schematic.
S1 Optional Rotary Switch, Your Choice on Positions.
C1 1 uF tant. @ 25 volts Min. C2 4.7 to 10 uF Tant. @ 10 Volts Min. C3 4.7 to 10 uF. tant. @ 10 Volts Min. C4 10 uF. Tant. @ 25 Volts Min. C5 100 uF. Electrolytic @ 25 Volts C6 1 uF. Tant. @ 10 Volts Min. C7 1 uF. Tant. @ 10 Volts Min. C8 4.7 to 10 uF. Tant. @ 10 Volts Min. C9 1 uF. Tant. @ 10 volts Min. C10 1 uF. Tant @ 10 Volts Min. C11 .1 uF Metalized Polyester Film Cap. NOTE: If you use the Optional Frequency Control Switch and Capacitors "C11a to C11e", Than OMIT C11. C11a These Values are Your Choice, Metalized Polyester Film Caps. C11b These Values are Your Choice, Metalized Polyester Film Caps. C11c These Values are Your Choice, Metalized Polyester Film Caps. C11d These Values are Your Choice, Metalized Polyester Film Caps. C11e These Values are Your Choice, Metalized Polyester Film Caps. C12 .01 @ 100 Volts " C13 .01 " " C14 .01 " " C15 .001 " " C16 .01 " " C17 .0047 " " C18 4.7 to 10 Mfd. Tant. @ 10 Volts Min. C19 47 or 100 Pf disk, depending on your requirements. C20 .01 @ 100 Volts Metalized Polyester Film Caps. C21 .01 " " C22 47 or 100 pf Disk, depending on your requirements. C25 .1 @ 63 Volts Metalized Polyester Film Caps. C26 .1 " C27 22 uF Electrolytic @ 10 Volts C28 .1 @ 63 Volts Metalized Polyester Film Caps. C29 .01 @ 63 Volts " " " " C30 .22 or .18 @ 63 volts " " " " C31 4.7 to 10 uF. Tant. @ 10 Volts Min. C33 4.7 to 10 uF. Tant. @ 10 Volts Min. C34 470 uF. Electrolytic @ 10 Volt Min.
D1 1N4937 "High Speed diode." D2 1N4937 "High Speed diode." D3 1N4148 or 1N914 D4 1N4148 or 1N914 D5 1N4148 or 1N914 D6 1N4148 or 1N914 D7 1N4148 or 1N914 D8 1N4148 or 1N914 D9 1N4148 or 1N914 for Expanded Meter D10 1N4148 or 1N914 for Expanded Meter
IC Sockets 8 each, 8 pin dips. Highly Recommended.
IC1 REG-1117A-adj (Surface mount "SOT-223" Package. Mounts on copper side.) OR a MC33269ST-ADJ ("SOT-223 Package" Adjustable version.) On Both these IC's, it is Not Recommended that you solder the Centre Lead. Just solder the Two Outside leads and the Heat Tab. IC2 LT1054-CN8 -(8 pin dip) "Substitute a ICL7660ACPA", it is much cheaper) ICL7660.....SEE NOTE AT BOTTOM! IC3 78L05 T0-92 pkg. IC4 79L05 T0-92 pkg. IC5 555 8 pin dip (C-mos version is acceptable) IC6 555 8 pin dip (C-mos version is acceptable) IC7 555 8 pin dip (C-mos version is acceptable) IC8 555 8 pin dip (C-mos version is acceptable) IC9 TL081 or TL071 8 pin dip IC10 TL081 or TL071 8 pin dip IC11 555 8 pin dip (C-mos version is acceptable)
Q1 IRF640 or IRF740 (You can cut off heat tab if you wish to reduce height.) Q2 IRF640 or IRF740 (You can cut off heat tab if you wish to reduce height.) Q3 2N3819 or 2SK30A(Check PINOUT, Before Installing) Q4 2N4125 or 2N3906 or almost any PNP type signal transistor will work.
M1 200 Ua. Meter (or 100 Ua. or 50 Ua., But you need to change R31 to double or 4 times the value) For Extreme sensitivity, use a 200 Ua. Digital Panal Meter. "This gives very accurate low level detection!"
SPKR Any speaker or headphones with a "Good Low Frequency Response". For stereo headphones use "tip to tip" connection, leave ground open.
LI Aprox 40 turns @ 6" OD, 30 Turns @ 8" OD, 25 Turns @ 12" OD. square, round, Or Whatever! I recommend around 20 AWG Wire (.032" or .8mm) L2 Same as L1 if used! See other Write-ups on the coils and coil forms!
BI 12 Volt, 1.2 AH Sealed Lead Acid Battery, Or Whatever at 12 Volts! DO NOT operate this unit at a supply voltage of less than 11 volts when calibrating unit, and Operating voltage must be greater than 10.5 volts, or unit becomes unstable in use. I recommend the Sealed Lead Acid as it is Relatively inexpensive and will usually last much longer than Ni-Cads. The only advantage I see to Ni-Cads is the faster Re-charge rate of about 1 hour. But Re-charging the Lead acid battery overnight is usually quite simple and poses no problem. If using Ni-Cads, I recommend 10 of them as the nominal output is 1.2 volts per cell. If using Standard AA Batteries, I recommend 8 of them, but this can get Expensive as they don't last very long if you use the detector a lot.
*** Contrary to the Data Sheet, I have found that The ICL7660CPA, Absolute Maximum Rated at 10.5 Volts, Works just fine, even when the battery is Fully charged at 14.5 volts!
There is a ICL7660ACPA which has an Absolute Maximum Rating of 13 Volts, These test the same as the ICL7660CPA!
Additionally there is a ICL7662CPA with an Absolute Maxium Voltage Rating of 22 Volts. It appears to be about 1/2 the price of the LT1054.
The LT1054 costs 4 times or More than the price of either of the ICL7660's! A BIG DIFFERENCE!
But the final Choice is Yours!
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