Импульсный металлоискатель Blind Squirrel

Список номиналов деталей под катом.

B1 3.6 v Lithium cell x 4 for a fully charge voltage of 16.8 volts.

C1 470 uF 25v
C2 100 uF 16v
C3 27 pF disc ceramic
C4 .1 uF mono ceramic
C5 .01 uF mylar
C6 .1 uF mono ceramic
C7 .0033 uF mylar
C8 .0033 uF mylar
C9 1 uF mono ceramic
C10 4.7 uF tantalum (or other low leakage type, if space permits)
C11 4.7 pF disc ceramic
C12 1 uF mono ceramic
C13 4.7 uF tantalum
C14 .001 uF mylar
C15 .01 uF mylar
C16 .1 uF mono ceramic
C17 .01 uF mylar
C18 1 uF mono ceramic
C19 .01 uF mylar
C20 .01 uF mylar
C21 .1 uF mono ceramic
C22 470 uF 16v

D1,D2,D3,D4 1N4148

L1 Search coil, 27 turns 9.5 inches O.D.# 20 enameled wire flat spiral wound.

M1 50 uA DC Ammeter 4N35

OC1 Opto Coupler

Q1 IRF740
Q2 MPSA70 or any general purpose PNP transistor with a beta of 40 or higher.

R1 3.3k
R2 25k pot.
R3 1.5k
R4 25k pot.
R5 1.5k
R6 25k pot.
R7 470 1⁄2 watt
R8 470
R9 220
R10 1 meg
R11 100k pot.
R12 10k
R13 1k (if using SEN. pot.) otherwise 10k to 15k
R14 100k pot. (short if not using SEN pot.)
R15 47k
R16 50k pot. ten turn
R17 100k
R18 220k
R19 33k
R20 22k
R21 33k
R22 33k
R23 100
R24 1k
R25 15
R26 220 (used only with piezo transducer)
R27 15
R28 1 meg

SPK 8 to 30 ohms

U1 4536B
U2 4538B
U3 LM318
U4 4066B
U5 ICL7621 (See Text)
U6 555

VR1 LD1085V12 Low dropout 12 volt 3 amp. positive regulator (Available from Digi-Key) XTAL1 3.579545 mHz. Crystal

You can select different frequencies in multiples of 2 by changing the binary code at A,B and C inputs. The following table shows the frequencies possible with a 3.579545 mHz. crystal:

C B A Frequency
0 0 0 6,991.298828 Hz.
0 0 1 3,495.649414 Hz.
0 1 0 1,747.824707 Hz.
0 1 1 873.91235 Hz.
1 0 0 436.956176 Hz.
1 0 1 218.4780884 Hz.
1 1 0 109.2390442 Hz.
1 1 1 54.61952209 Hz.