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Simple Circuit BFO metal Detector - Not the best, but Simple, and Now with a PCB. __ Designed by G.L. Chemelec
Simple Circuit BFO Metal Detector - BFO (beat frequency oscillator) metal detectors use two oscillators, each of which produces a radio frequency. One of these oscillators uses a coil of wire that we call the search loop. The second oscillator uses a much smaller coil of wire, and is usually inside the control box and is called the reference oscillator. By adjusting the oscillators so their frequencies are very nearly the same, the difference between them is made audible as a beat note __ Designed by Essex Metal Detectors
Simple Circuit BFO Metal Detector - This simple BFO metal detector requires only a few of components and an evening's work. The two oscillators are simple Colpitts designs using BJT transistors. The reference oscillator's frequency is approximately 370kHz, slightly tunable with the help of a silicon varactor diode. The outputs of the two oscillators are fed to a mixer made with Q3 and Q4. The signal then goes through a low-pass filter (R13, C13) and a JFET preamp. The LM386 audio amplifier has a gain of 20, more than enough for most headphones. if you need more gain, you can add a 10uF capacitor between pins 1 and 8.__ hobbyteam @ hobby-hour.com
Simple Circuit metal Detector Electronic - All the parts for the PC board, PC board, battery and winding wire $10.00 including pack and post. You will also need an AM radio, base-board to mount the parts and a wooden handle approx 1.5 metres long. __ Designed by Collin Mitchell
Simple Circuit VLF, PI & BFO - Metal detector theory - Metal detectors are used in a wide range of applications from landmine detection to safety in airports, office buildings or schools. They can also be useful around the house to help locate lost coins, jewelry, keys and gas lines.__ hobbyteam @ hobby-hour.com
Simple Metal Detector - Two transistors and a LM386 make a simple metal detector suitable for finding coins. __ Designed by Steve Hagerman
Single Chip Metal Detecor - A single chip metal detector with a range of a few inches. This is useful for decting nails or screws in walls and floors, or for locating buried mains cable. __ Designed by Andy Collison
Testing Metal Detector Coils - I Decided to Check my coils for inter-wire and Total Capacitance. it is a Well Known fact that internal Capacitance in a coil reduces its frequency response. in the Tests Below, The coil Lead Lengths on all coils was about 5 inches. No Coax cable used __ Designed by G.L. Chemelec
The "Matchless" Metal Locator - it's cheap, its easy to build and it could find a fortune.__ SiliconChip
Two-component metal Detector - The circuit shown must represent the limits of simplicity for a metal detector. it uses a single 4093 quad Schmitt NAND IC and a search coil -- and of course a switch and batteries. A lead from IC 1d pin 11 needs to be attached to a MW radio aerial, or should be wrapped around the radio. if the radio has a BFO switch, switch this ON. Since an inductor resists rapid changes in voltage (called reactance) , any change in the logic level at IC 1c pin 10 is delayed during transfer back to input pins 1 and 2. This is further delayed through propagation delays within the 4093 IC . This sets up a __ Designed by © Rev. Thomas Scarborough
Two-component metal Detector using a 4093 - The circuit shown must represent the limits of simplicity for a metal detector. it uses a single 4093 quad Schmitt NAND IC and a search coil — and of course a switch and batteries. A lead from IC 1d pin 11 needs to be attached to a MW radio aerial, or should be wrapped around the radio. if the radio has a BFO switch, switch this ON. __ Designed by Rev. Thomas Scarborough
White's SurFMaster PI (pulse induction) metal Detector schematic diagram - White's Surfmaster PI is a good quality, fully waterproof, lightweight metal detector with an exceptional depth in saltwater or mineralized ground. it's ideal for those wishing to search beaches, in the surf or shallow diving. it works inland too, but such use is not advised as -- like all PI (Pulse induction) designs -- there is no effective discrimination of ferrous objects. Runs on eight AA size batteries. __ Contact hobbyteam @ hobby-hour.com
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