IDX-PRO+VDI

[bernte_one]

hello darek
you can use a simple prebuild amplifier board
http://www.ebay.de/itm/Amplifier-Boa...item3a964ba481

[dAYek]

Hello bernte_one and thanks for your reply.
I do not think it is necessary to use such a big two-way amplifier...
To be more precise - we have removed R40 100K resistor and used a 10k potentiometer with 2k5 resistor to be able to controll the volume level.
I have some experience with White's PRL-1 (without volume level controll) and believe me - the noise is much too loud.
But in our case although the potentiometer is in it's max position, the speaker is barely heard.
Hope it is more clear now.
Any help more than welcome.
Darek

[Koala]

Hello bernte_one and thanks for your reply.
I do not think it is necessary to use such a big two-way amplifier...
To be more precise - we have removed R40 100K resistor and used a 10k potentiometer with 2k5 resistor to be able to controll the volume level.
I have some experience with White's PRL-1 (without volume level controll) and believe me - the noise is much too loud.
But in our case although the potentiometer is in it's max position, the speaker is barely heard.
Hope it is more clear now.
Any help more than welcome.
Darek

Did you use a MPSA13 or an alternative.

[der_fisherman]

Hello guys.
My name is Darek and I am writing from Poland.
Thanks to this topic we have finally built ourown IDX PROs - PCB kits from Andy the Silverdog, shaft from Armand detectors, DD coil built completely on ourown.
But we have a problem with volume control...
We have already changed the piezzo speakers to bigger speakers (one taken out of a telephone handspeaker and one taken out of the computer - typical 8 Ohm and 0.5W one) but still, the voice level is too low :-(. The speaker can be heard while working in the wood or in an abondonded field but not in the neighbourhood of the households or a road. On Sunday I was trying to use it next to a guy using two tone Technotics and I could not hear anything... So the question is - what can be done to make the detector louder? Cause as I have already mentioned - a bigger speaker is not a solution...
I am looking forward to hearing from you - more experienced guys.
Darek

You often get better volume (it depends upon circuit design) by using a speaker with a higher impedance, over 36 Ohms for example...is my experience anyway. They are the ones for attaching to MP3 players and the like.
Remember, the higher the cost, the lower the volume, in this example, cheap will be the loudest usually....so a cheap speaker of close to 40 ohms or so....
regards
Andy

[dAYek]

MPSA13

[nelson]

Hi

I just got a used Whites IDX Pro and i already have done threshold and ground balance mods. The detector works excellent, good discrimination, very accurate, a nice machine that can compete with other higer priced detectors.
Now i will like to add two tone sound, so if anyone can help me with detail instructions, i will apreciate it.
Best regards
Nelson

[jlsilicon]

Just the regular POLY FILM Green Blob Caps will be good enough ?

How about MultiLayer Ceramic Capacitors at 2% ?

[Koala]

MPSA13

MPSA14 is a pin for pin swap with a higher gain. Not tried one myself. If you search this thread I had a problem with depth in PP mode due to low volume. Never got round to changing to MPSA14 as I now use different headphones.

You do need to use headphone with this detector as the deeper the target the quieter the sound(depth feedback). In DISC mode you can turn the threshold up to make the deeper signal louder but you loose the feedback of how deep a target is.

[Koala]

How about MultiLayer Ceramic Capacitors at 2% ?

Quick answer NO

Film capacitors are more linear and are better for analog detectors

[jlsilicon]

Quick answer NO

Film capacitors are more linear and are better for analog detectors

-> So np0 Caps should be perfect then ?

[Koala]

-> So np0 Caps should be perfect then ?

Don't see whats the problem using polyester capacitors. There is nothing to be gained here for our application. Cheapish and available in all sizes.

look here http://forum.allaboutcircuits.com/th...pacitor.42445/

NP0 are normally only available in very small sizes

I have assumed you are making a through plate board and not surface mount.

[jlsilicon]

Don't see whats the problem using polyester capacitors. There is nothing to be gained here for our application. Cheapish and available in all sizes.

look here http://forum.allaboutcircuits.com/th...pacitor.42445/

NP0 are normally only available in very small sizes

I have assumed you are making a through plate board and not surface mount.

Thanks - Interesting Article.

But, my Metal Detector Projects seem to have a drifting pitch up or down over the span of 1 or 2 minutes - even with the Polyester caps.

For example, one Oscillator project that I was testing last night:
- Just a 2n3904 , a 10K resistor , and (2) 0.1uf polyester caps (little red squares 1/2cm across - mica I believe).
On my Datascope, it showed a drift from 60khz up to 100khz over about 1 minute time
- until I powered it down for a few minutes to repeat the same results again ... and again.

[Koala]

I have built the IDX with no mods and poly caps no drift. 8AA batteries run for at least 30+ hours.

Switch on set ground balance and threshold. Detect for 8 hours or more with no more adjustments. Might adjust the ground more positive if fired coke is giving a positive signal that's it.

Great project. Everything works as it should. Just build as is.

Only thing I have found that affects it is if you are 50 yards from an electric train line you can tell 5 min before that a train is coming past.

[Gwil]

Hi jlsilicon

Something strange here - "(2) 0.1uf polyester caps (little red squares 1/2cm across - mica I believe)". Are you sure you mean polyester?
A 0.1uF capacitor 5mm square is almost certainly a ceramic type, I honestly doubt if a polyester one could be made that small. And definitely not mica, a mica 0.1uF would be the size of a brick.

Could you post the schematic of your oscillator? I'm intrigued.

Gwil

[Koala]

Hi jlsilicon

Something strange here - "(2) 0.1uf polyester caps (little red squares 1/2cm across - mica I believe)". Are you sure you mean polyester?
A 0.1uF capacitor 5mm square is almost certainly a ceramic type, I honestly doubt if a polyester one could be made that small. And definitely not mica, a mica 0.1uF would be the size of a brick.

Could you post the schematic of your oscillator? I'm intrigued.

Gwil

original board as supplied by whites C2,C20 and C24 were the only ones that were ceramic all others were polyester and a few polarized . I did not use any ceramic for small values I used radial leads they fitted in twisted around a bit. Some photos of my board are further back on this thread somewhere.


http://www.taydaelectronics.com/capa...apacitors.html

5mm lead spacing and that's for a 100v version