PI MD

[green]

Finally got the circuits wired and working on the bench. Three separate circuits, (coil driver and power supplies), (control logic), (preamp, integrators and post amplifiers). Have been using +battery for analog common with a -regulator for the -rail(digital and analog) with a separate battery and a +regulator for the +rail(digital and analog). Since I'm using an IB coil I tried something from the Surf master II thread. -battery for -rail(digital and analog) +regulator for +digital rail and a different +regulator for +analog rail with a TLE2426 rail splitter across the analog supply for analog common. Added the coil on integrator switch control signal to control logic(starts integrating about 10usec after coil on, stops integrating at coil turn off), better if stopped integrating 1/2usec before coil turn off(will change). Coil on integrator out signal polarity for ferrous targets including ground, hot rock and brick opposite non ferrous targets. Was hoping to put circuits in a box and try on the ground but I had a bad connection on the control card loading the digital power supply. Finally got it working. After looking at the solder joints to the SMD chips with a magnifying glass I don't think it would be reliable on the ground. Need to order some SMD adaptors and rewire. The GEB circuit works but I keep changing what to change to adjust GEB. Now I'm thinking target delay adjustable 7 to 15usec, target sample adjustable 8 to 20usec(GEB adjust), GEB delay 1usec, GEB sample 100usec. It's a learning experiment. A simple PI with GEB and maybe ferrous indication. I think it will depend on signal to noise ratio if it makes a metal detector.

[green]

Getting ready to start MD build. A block diagram of what I'm thinking. Was trying to figure out how to change sound to identify targets. Have been using a voltmeter looking at integrator out on the bench, works good. Thinking it might work on the ground. Use sound and motion to find the target and the meter reading to identify(coil on for ferrous non ferrous)(coil off for short and long time constant targets). Wondering if gains and frequency cutoff make sense or anything else that might need changing or adding. A cheap multi meter could be used. 2volts FS gives 330nv/digit at the coil. Could be used to check battery volts.