This appears to be a variant of the Russian Pirat pulse induction detector, which can be a very effective machine, so long as there is not much trash in the ground. I built mine about 6 months ago, and can offer a couple of tips. 1 adjust the 555 output to be 150 Hz. 2 The LM 358 op amp can be used in place of the Soviet chip. Be advised that the pinout is different. 3 Bring the power leads in to the rails as close as possible to the Moffett location. 4 This thing is power hungry, I used an 11.4 volt airsoft battery with good results. 5 Make your coil with a high Q factor, tightly wound, and bound with thread. Wrap a narrow strip of aluminum foil around the coil for shielding, but be sure to leave a 1 inch gap at the ends. If the foil goes completely around the circumference of the coil it will be a shorted turn and will not work. Connect this shield to battery ground. 6 Finally, use shielded cable for the connection from the coil to the circuit board. It is a fun project and you can learn a lot from it. My Pirat will detect coins at 8 to 10 inches and large objects at 3 feet. It took some tweaking resistor values to get it there, but I think that it is one of the best diy options out there. Have fun!
This appears to be a variant of the Russian Pirat pulse induction detector, which can be a very effective machine, so long as there is not much trash in the ground. I built mine about 6 months ago, and can offer a couple of tips.
1 adjust the 555 output to be 150 Hz.
2 The LM 358 op amp can be used in place of the Soviet chip. Be advised that the pinout is different.
3 Bring the power leads in to the rails as close as possible to the Moffett location.
4 This thing is power hungry, I used an 11.4 volt airsoft battery with good results.
5 Make your coil with a high Q factor, tightly wound, and bound with thread. Wrap a narrow strip of aluminum foil around the coil for shielding, but be sure to leave a 1 inch gap at the ends. If the foil goes completely around the circumference of the coil it will be a shorted turn and will not work. Connect this shield to battery ground.
6 Finally, use shielded cable for the connection from the coil to the circuit board.
It is a fun project and you can learn a lot from it. My Pirat will detect coins at 8 to 10 inches and large objects at 3 feet. It took some tweaking resistor values to get it there, but I think that it is one of the best diy options out there.
Have fun!