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Hi all,
It was suggested I open a thread about this unit, as it is possible that it could be hacked modified or otherwise improved (and it needs some...).
I'll post some more images in the next post.
The TX-2002 is a cheap Chinese pinpointer made by http://www.shtianxun.cn/infoi.aspx?Class_id=36
I bought it to see if it was any good for pinpointing at the beach, but really I could live without one there.
My opinion of it is not high, it seems to be a motion detector (needing constant moving to keep indicating a metal target) and seems to be very insensitive. With an Australian $1 coin in air I get at very best 20mm with the coin flat side on, and only 3mm with it edge on. So most of the time I can see the coin before I can detect it
I've tried a few tweaks to see if I can more sensitivity out of it, but no. I made a trivial increase by adding an extra 22nF cap across the search coil (two wire, ferrite rod type, 2 ohms). Also tried other things, including trying about four different brand LM358's I had in my parts bins. I noted that the unit could have a vibrator motor installed on it, the tracks and component pads are there, and the buzzer on/off switch is actually a change-over that connects to the vibrator circuit. But I see little point unless sensitivity is improved...
I made a start at creating a schematic, but as it's not a trivial circuit I stopped after realised I may actually replace the whole board in the future anyway.
It may be a good cheap candidate to put in the circuit described here http://www.geotech1.com/forums/showt...tector-project
The search coil L value I'll measure in a few days (when I can get to an L meter). The coil has a 22nF cap in parallel with it forming a resonant circuit. The oscillation frequency is around 20kHz when measured on the hot side of the coil, not 90kHz like the user manual says !
(The CRO image frequency was with the extra 22nF cap fitted BTW). The oscillation frequency drops slightly (say around 100-200Hz) in the presence of metal, but the main circuit seems to track it so unless you move the metal out of the search coil field again you don't get another beep out of the buzzer.
If anyone knows more about the unit please add comment posts. I thought it was going to be like a Cen-Tech circuit, but it's not.
Cheers,
Martin
As it was when first opened (prior to my first molestations).
It was suggested I open a thread about this unit, as it is possible that it could be hacked modified or otherwise improved (and it needs some...).
I'll post some more images in the next post.
The TX-2002 is a cheap Chinese pinpointer made by http://www.shtianxun.cn/infoi.aspx?Class_id=36
I bought it to see if it was any good for pinpointing at the beach, but really I could live without one there.
My opinion of it is not high, it seems to be a motion detector (needing constant moving to keep indicating a metal target) and seems to be very insensitive. With an Australian $1 coin in air I get at very best 20mm with the coin flat side on, and only 3mm with it edge on. So most of the time I can see the coin before I can detect it
I've tried a few tweaks to see if I can more sensitivity out of it, but no. I made a trivial increase by adding an extra 22nF cap across the search coil (two wire, ferrite rod type, 2 ohms). Also tried other things, including trying about four different brand LM358's I had in my parts bins. I noted that the unit could have a vibrator motor installed on it, the tracks and component pads are there, and the buzzer on/off switch is actually a change-over that connects to the vibrator circuit. But I see little point unless sensitivity is improved...
I made a start at creating a schematic, but as it's not a trivial circuit I stopped after realised I may actually replace the whole board in the future anyway.
It may be a good cheap candidate to put in the circuit described here http://www.geotech1.com/forums/showt...tector-project
The search coil L value I'll measure in a few days (when I can get to an L meter). The coil has a 22nF cap in parallel with it forming a resonant circuit. The oscillation frequency is around 20kHz when measured on the hot side of the coil, not 90kHz like the user manual says !
(The CRO image frequency was with the extra 22nF cap fitted BTW). The oscillation frequency drops slightly (say around 100-200Hz) in the presence of metal, but the main circuit seems to track it so unless you move the metal out of the search coil field again you don't get another beep out of the buzzer.
If anyone knows more about the unit please add comment posts. I thought it was going to be like a Cen-Tech circuit, but it's not.
Cheers,
Martin
As it was when first opened (prior to my first molestations).
. I took 44nF and 17kHz for calculation.
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