IDX-PRO+VDI

[Sun_rise_pt]

R25 may be impossible to make any adjustments due to considerable resistance of 47 Ohm to block the voltage variation. I do not understand that someone may have mounted the IDX Pro without changing it, and still get good results of operations.

The difference in behavior of the op amp U4 is considerably different than if you used a 1N4148 diode (app. 0.6 V voltage barrier) in the feedback control, or a 2.7V zener that has ...
White, who is the source of the IDX Pro, has always used the zener.

[Merc]

I note some anomalies between the disposition of the components in Sprint layout and schematic and too the part list posted here.

- The diode D3 is shown in the layout in the inverted position and will not be a 1N4148, but a 2.7 volt zener.

The value of R25 (47 Ohm) shown in the layout is wrong, because it is relatively low extramamente linked directly to the circuit that would block any adjustment P5. I think the value of R25 (10k) indicated in the diagram will be the correct ...

---
I have two questions to put to the friends who built the IDX Pro:
- What is the consumption (mA) of the circuit?
- How to adjust VR3 should be adjusted?
- Does anyone have the oscillograms for the different stages?

I would agree that the sensitivity circuit is not quite correct. My IDX works, but there is little to no sensitivity adjustment. I changed R25 to a 10K as on the schematic and I lifted the 1M resistor in that circuit. I now have way too much adjustment range I think. I'm still trying to fine tune that part of the detector.

As for VR3, take a look at the schematic for the White's Coinmaster Classic series which can be found on this site. It shows a variable resistor in that same part of the schematic and it is labeled "Screw Cap Reject". Perhaps this sets the discrimination range? I'm not sure yet.

As for D3, I do see a zener shown on schematic, however, my detector is working with a 1N4148 in that location.

Merc

[mikebg]

REDESIGNED TX

This posting is continuation of posting # 612 where are described disadvantages of the original TX used in Classic family.
Here is attached the circuit diagram of redesigned TX. The SPICE analysis shown below was made with CircuitMaker. This design has the following advantages:

1. High power and efficiency. It delivers to TX coil almost rail to rail amplitude of voltage. For example, in Classic family, we will obtain 15.6Vpp across TX coil because there is 8V between supply rails. The current in tank circuit will be 300 mA amplitude at 1.5ohm TX coil. This is almost twice the value of original Classic circuit.

2. Ampereturns and efficiency can be increased even more if the redesigned TX is powered direct from battery rails. This method is used by Minelab in several models. Note that the redesigned circuit seems like TX circuits used in Musketeer and Relic Hawk, but small important differences make it to operate much more efficient.

3. Precise and quick dismodulation of TX. This is achieved with PID controller. Transistor Q2 pumps tank circuit with pulses having less than 50% duty cycle even when TX coil is almost on the salt water surface. You can measure with SPICE and test in practice how TX circuit increases battery drain when TX coil moves closer to stron absorbing ground.

4. Wide range of supply voltage. The efficiency remains maximal when battery voltage changes in range 6V ... 13.6V. This is achieved with diode D2, used as nonlinear resistor in voltage divider R5, R6, R7.

This TX circuit is preferable for every VLF metal detector, not only for Classic family.

[eduardo1979]

Apparently the images PCBs for sale are not correct.
I believe that some of hobbyists are serious difficulties in assembling the circuit.
Even more personal connected to the technical area, the IDX Pro requires at least an oscilloscope to a perfect adjustment of the phase synchronous detector (discriminator).

It would be great if some of our friends who've built this circuit that can publish here oscillograms of the various stages, with reference to the wave of TX, because it certainly would save huge headaches for manufacturers.
Another simple to solve in Sprint Layout is the question of positioning pins of the transistors for the design of the capsule positioning them online

All PCBs are correct. There is no error.Yo have made over 20 IDX-PRO and all worked well. The problem is people do not understand much rookie electronics. SilverDog PCBs are correct. The secret is the coil and adjusting the phase and the capacitors of TX and RX

[Sun_rise_pt]

Apparently the images PCBs for sale are not correct.
I believe that some of hobbyists are serious difficulties in assembling the circuit.
Even more personal connected to the technical area, the IDX Pro requires at least an oscilloscope to a perfect adjustment of the phase synchronous detector (discriminator).

It would be great if some of our friends who've built this circuit that can publish here oscillograms of the various stages, with reference to the wave of TX, because it certainly would save huge headaches for manufacturers.
Another simple to solve in Sprint Layout is the question of positioning pins of the transistors for the design of the capsule positioning them online

[Schatztaucher]

I suppose eduardo has made the changes. The thing with the diode discussed in the Russian forum too. with an 8 ohm speaker, the MPSA13 burned again. Thursday I'll try it with a piezo speaker.
silverdog idx works but also ..... but how?

regards, marc

[Sun_rise_pt]

I note some anomalies between the disposition of the components in Sprint layout and schematic and too the part list posted here.

- The diode D3 is shown in the layout in the inverted position and will not be a 1N4148, but a 2.7 volt zener.

The value of R25 (47 Ohm) shown in the layout is wrong, because it is relatively low extramamente linked directly to the circuit that would block any adjustment P5. I think the value of R25 (10k) indicated in the diagram will be the correct ...

---
I have two questions to put to the friends who built the IDX Pro:
- What is the consumption (mA) of the circuit?
- How to adjust VR3 should be adjusted?
- Does anyone have the oscillograms for the different stages?

[szucs_g]

Coil

I measured it White's 3900 pro his coil. The between 4-5 legs 12,9 mH measured. 1,7 are mH between 1-2. May this IDX be good? The official description 6,5 MHz grants.

[eduardo1979]

There are many versions of IDX and Classic 3. You always have to experiment and make the most of the projects. I have made 4 or 5 versions of these and todabia I have much to prove. Right now I'm very happy with my IDX-PRO.

[szucs_g]

FOR ALL.

The first reported plan realized. There are to R2, R31, R35 others. This does not affect its operation? Otherwise, the main difference is now I have not seen much published version. Thank you for your answer!

[Tepco]

OK, previous post was my mistake, but to explain: Coil made to this specification will be initially way off, somewhat larger TX inductance, and way higher, almost double, on RX side, so some tuning whit capacitors is necessary, on RX side ended up whit 22 nF or something close, I don’t want to speculate, i have written down values somewhere and will post exact measurement data. Anyway, coil made like this will be off specs and must be tuned, then it will work quite nice.

[Tepco]

Whit 420 turns on RX side, inductance will be significantly higher than original, so some adjustment of RX capacitor is necessary (22nF instead of 33 nF as I can remember, or something like this) to keep it tuned right.

[Schatztaucher]

these data are also in the thread ......

- tx winding diameter 20cm ! tx 0.70mm, -35 winding !


- rx winding diameter 10cm! rx 0.18mm,- 420 winding !
Data for the concentric



- feedback loop , diameter 9,5cm ,15-17- winding !
wire 0.70mm .
Data for the concentric coil !!!
black max coil !!!

[eduardo1979]

Both versions are correct. When connecting the PCB 2-tone to PCB metal detector, you have to remove the R55 on the PCB of the detector.

[verotopasera]

AUDIO 2 TONES

hello eduardo1979 which method of connection is correct