Pulse Induction Metal Detectors

SurfPI Pro metal detector

Pulsed metal detector White SurfPI Pro, which is used for underwater search by professional. Fully sealed to a depth of 30 m. Successfully working in sea water and on highly mineralized soil. Metal detector White Surfpi is also well suited for ground search in wet sand. It has a custom sound threshold to achieve the greatest depth of search in any conditions. There is no effective discrimination of ferrous objects.

SurfPI Pro metal detector


1- 12 x 6″ Dual coil design that offers superb sensitivity on all targets
2- Adjustable Pulse Delay reduces black sand “noise.”
3- Quiet beaches – more targets
4- Exceptional depth on coins and jewelry, especially in saltwater and mineralized ground
5- Enhanced sensitivity to gold jewelry at maximum depths
6- Gain control adjusts for any particular beach conditions
7- Quick Target Recovery so you hear good targets even mixed in with junk
8- Tuner Control adjusts the threshold tone and checks battery strength
9- Automatic Ground Rejection10- Near-neutral loop buoyancy
11- Power Supply: 8 AA batteries for up to 25 hours of hunting
12- Headphones are hardwired into the unit, not removable

SurfPI Pro Schematic

SurfPI Pro metal detector

SurfPI Pro partlist


C1 22 nF [Stacked polyester film (+/-5%)]
C2 1000 uF electrolytic 25 volts
C3 100 nF [polyester box (+/-5%)]
C4 100 nF [polyester box (+/-5%)]
C5 220 nF [polyester box (+/-5%)]
C6 220 nF [polyester box (+/-5%)]
C7 1 uF [polyester box (+/-5%)]
C8 47 nF [Stacked polyester film (+/-5%)]
C9 1 nF [Stacked polyester film (+/-5%)]
C10 1 nF [Stacked polyester film (+/-5%)]
C11 1 nF [Stacked polyester film (+/-5%)]
C12 1 nF [Stacked polyester film (+/-5%)]
C13 220 uF electrolytic 16 volts
C14 220 uF electrolytic 16 volts
C15 220 uF electrolytic 16 volts
C16 100 nF [polyester box (+/-5%)
C17 100 nF [polyester box (+/-5%)
C19 220 uf electrolytic 16 volts
C20 100pf Monolythic Ceramic


D1 1N4148
D2 1N4148
D3 1N4148
D4 1N5819
D6 1N4001

Integrated Circuits

U1 TLC555
U2 NE5534
U3 LM358
U4 CD4093
U5 78L05
U6 ICL7660
U7 CD4066


R1 100k [metal film 1%]
R2 5k (trimmer) set at 3.3k
R3 3k3 [metal film 1%]
R4 2k2 [metal film 1%]
R5 1k5 [metal film 1%]
R6 390 Ohm 2W [metal film 1%]
R7 1k [metal film 1%]
R8 1k [metal film 1%]
R9 1M [metal film 1%]
R10 100k (trimmer) offset
R11 22k [metal film 1%]
R12 10k [metal film 1%]
R13 1k [metal film 1%]
R14 1k [metal film 1%]
R15 470k [metal film 1%]
R16 470k [metal film 1%]
R17 10k [metal film 1%]
R18 47k [metal film 1%]
R19 10k Pot. [Threshold]
R20 47k [metal film 1%]
R21 1k [metal film 1%]
R22 220k [metal film 1%]
R23 22k [metal film 1%]
R24 1K Pot [Volume]
R25 5k1 [metal film 1%]
R26 51k [metal film 1%]
R27 12 Ohm 1/2Watt [metal film 1%]
R28 240k [metal film 1%]
R29 51k [metal film 1%]
R30 – 10K Potentiometer [Pulse Delay]
R31 100k Pot. Sensitivity
R34 150 Ohm [metal film 1%]
R35 100k [metal film 1%]

Q1 2N3906
Q2 IRF9640


  • All resistors 1/4 watt +/-5% unless noted otherwise
  • Capacitors with values greater than 1uF are aluminium electrolytics (+80%, -20%)
  • Capacitors with values less than 1uF are polyester film type (+/-10%)
  • Nominal capacitor range of 0.001-0.39uF = polyester film.
  • Nominal capacitor range of 0.047-1uF = stacked polyester film.
  • ST = Stacked polyester (Panasonic “V” series) +/-5%.
  • Simple mod: If TIP32C (Q2) gets excessively hot, use an IRF9640 MOSFET instead. Experiment with different values for R6 to find the optimal value (I use a 390 ohm resistor). Temporarily substitute R6 for a trim potentiometer (470Ω or 1kΩ) to find the optimal dumping resistor for your coil.

Surf PI Pro PCBs

Many PCBs have been developed for the metal detector Surf Pi,

This is a PCB of the version 1.2 of Surf PI metal detector based on two sides PCB

SurfPI Pro metal detector
SurfPI Pro metal detector

Toner Transfer PCB methodThis second version of the  PCB   version 1.2 is modified for one side PCB for home manufacturing.

SurfPI Pro metal detector
SurfPI Pro metal detector

The next PCB is based on the original version of the Surf PI metal detector with some arrangement of components. This version (Surf PI XX) is more discussed in forums.

SurfPI Pro metal detector
SurfPI Pro metal detector

Its easy to assemble even for beginners. If you avoid making mistakes during assembly, it works right directly. The narrow version of the board allows you to use an empty tube from building sealants or a piece of 50mm sewer plastic pipe as the body. Such an apparatus is compact and airtight. Well suited for beach and underwater searches.g

SurfPI Pro metal detector
SurfPI Pro metal detector
SurfPI Pro metal detector
SurfPI Pro metal detector
SurfPI Pro metal detector
SurfPI Pro metal detector

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