Terminator 3 metal detector

Terminator 3 is a coin searching metal detector that operates according to the induction balance principle (IB). The “Terminator-3” scheme was developed based on the Tesoro metal detector. However, there are significant differences from these metal detectors, both in its work principle, in the process of its manufacture or configuration.
The main advantage of the Terminator-3 metal detector is the ability to recognize metal at the limit of sensitivity (even with a minimal capture of the target, it accurately detects its kind).

Terminator 3 metal detector

Technical characteristics of the metal detector Terminator 3

– Principle of Operation IB (Induction Balance)
– The search modes “Discrimination” and “All Metals” are switched.
– Operating frequency 7–20 kHz (Depends on the coil and capacitors C1 and C2).
– Power 9-12 V.
– Manual ground balance
– Depth of detection of objects in the ground with a coil of 240 mm:
– Coin 5 Russian rubles – 22-24 cm.
– Coin 5 kopecks Catherine – up to 30 cm.
–  Helmet – up to 80 cm.

The division of the VDI scale in the Terminator-3 metal detector is graphically presented below.

Terminator 3 metal detector

Terminator- 3: scheme and part list

Terminator-3 is quite difficult to build it yourself. It will be extremely difficult for a beginner to do this. We recommend collecting this scheme for amateurs who have experience in the manufacture of metal detectors!.

Terminator 3 metal detector

C1.1 – 330nf       c16 – 220nf     c33 – 680nf
C1.2 – 330nf       c17 – 220nf     c34 – 1500mf x 10v
C2.1 – 150nf       c18 – 220nf     c35 – 470mf x 10v
C2.2 – 15nf        c19 – 220nf     c36 – 470nf
C3 – 3,3nf          c20 – 2,2m      c37 – 1000mf x 6,3v
C4 – 3,3nf         c21 – 470nf      c38 – 1000mf x 6,3v
C5 – 1000pf        c22 – 470nf     c39 – 470nf
C6 – 120pf         c23 – 47nf       c40 – 1mf x 160v
C7 – 560pf         c24 – 47nf       c41 – 2,2mf
C8 – 39pf          c25 – 4,7nf       c42 – 560pf
C9 – 360pf         c26 – 4,7nf       c43 – 330pf
C10 – 1000pf      c27 – 470nf
C11 – 1000pf      c28 – 470nf
C12 – 412pf       c29 – 47nf
C13 – 10nf         c30 – 47nf
C14 – 10nf         c31 – 680nf
C15 – 2,2nf        c32 – 680nf


R1 – 100k        r16 – 30k         r31 – 470k
R2 – 22om        r17 – 1k          r32 – 47k
R3 – 100k        r18 – 100om       r33 – 47k
R4 – 10k         r19 – 15k          r34 – 470k
R5 – 300k        r20 – 15k         r35 – 470k
R6 – 2,4k        r21 – 5,1k        r36 – 30k
R7 – 100k        r22 – 47k         r37 – 30k
R8 – 100k        r23 – 47k         r38 – 24k
R9 – 2,4k         r24 – 470k       r39 – 10k 
R10 – 1,5m      r25 – 470k        r40 – 24k
R11 – 1,5m       r26 - 47k        r41 – 15k
R12 – 100k       r27 – 1k          r42 – 24k
R13 – 110k       r28 – 47k        r43 – 100k
R14 – 470k       r29 – 330om
R15 – 100k       r30 – 470k
ICs                    Transistors      Diodes
Мс1 – HEF4069UBP           VT1 – BC327-40         VD1 – 1N4148
MC2 - HEF4069UBP           VT2 – BC327-40        VD2 – 1N4148
MC3 - HEF4069UBP           VT3 – 2SC4204         VD3 – Led
MC4 – 74HC4066N            VT4 – BC517            VD4 – FR157
MC5 - HEF4069UBP
MC6 - HEF4069UBP
MC7 - HEF4069UBP
MC8 – LM193N
MC9 – KP1170EH6
MC10 – KP1171CП64
MC11 – TL431ACLP

In addition, to create a Terminator-3 metal detector with your own hands, you need to prepare:

– Multimeter with capacitance measurement;
– Oscilloscope;
– LC meter.

Printed circuit board (PCB)

Several versions of PCB breeding for the Terminator-3 metal detector can be downloaded from the archive at the end of the post.

Terminator 3 metal detector
Terminator 3 metal detector
Terminator 3 metal detector

The capacitors on the board must be metal-film with high thermal stability. In addition, it is recommended using a tester to select the most identical parts in terms of parameters on two parallel amplification stages and the values of the capacitors C1 and C2, so that everything is as identical as possible. This will greatly facilitate your setup. As a tuning resistor, it is better to use multi-turn.

After soldering the metal detector, the board must be washed with alcohol, dried and visually checked for defects or any shot-circuit.

Then without a search coil, it is already possible to check its performance. For this:

1- Turn on the metal detector.
2- We unscrew the sensitivity regulator until a constant sound appears in the dynamics.
3- We touch the fingers of the sensor connector, the sound should be interrupted for a second.
4- When turned on, the LED should blink and turn off.

Terminator-3 metal detector

If so, and the board is soldered correctly. Now you can begin to manufacture the search coil.

Building a coil for the Terminator-3 :

TX – transmitting coil. Diameter 200mm
number of turns: 30 turns with a double folded wire
wire diameter: 0.4 enamelled winding
RX – receiving coil. Diameter 100mm
Number of turns: 48 turns with a double folded wire
Wire diameter: 0.4 enamelled winding
CX – compensation coil
Wire 0.4, wound on a mandrel from TX, the number of turns from 20 and rewind when setting the balance.

Terminator 3 metal detector

Both the transmitting and receiving coils are wound with a double wire (that is, 4 ends of the wire should be obtained), the shoulders of the windings are determined by the tester and we connect the beginning of one shoulder with the end of the other, we get the average output of the coil. The average output of TX is connected to the minus (Ground)  of the board (without this, the generator will not start), the average output of RX is needed only for tuning in frequency, after tuning in frequency (resonance) it is isolated and the receiving coil turns into normal (without output). The receiver for tuning is connected instead of the transmitter and tuned to 100Hz-150Hz below the transmitter. Balancing is carried out by a compensation coil by unwinding coils from it after all frequency settings. The balance should be within 100mv.

We spill the sensor with epoxy resin, but only at half the depth of the mold. After solidification, we connect the oscilloscope, bend our loop into the form and begin to twist it, trying to find the minimum amplitude value. After the position is found, fix the loop with glue, re-check the balance and fill our form to the end.
below the finished home-made coil for a metal detector Terminator-3.

Firstly, after balancing, check the connection. The metal discrimination knob is set to zero, the ground balance knob is in the middle position, the feeling knob is adjusted, the mode dial is in the “color only” position.

We take a piece of ferrite 1x1cm and some copper pieces. We turn on the device and the first wave the ferrite over the sensor, then the copper. There should be a double beep on ferrite, and a single beep on copper. If vice versa – then we change the ends in TX places.

Download necessary files

1- Printed circuit board PCB 1
2- Printed circuit board PCB 2
3- Printed circuit board PCB 3
4- SMD printed circuit bord (SMD PCB 1)
5- SMD printed circuit bord  PCB 5
6- SMD printed circuit bord (SMD PCB 2)

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