PI from Poland ???

[pelanj]

Wow, great, thanks a lot. I think I will make a nice coil first and then make the circuit mods. I was thinking about changing the round coil into an eliptic shape - as pinpointing is quite difficult with a large round coil.

[Pepe LeMiau]

I've been studying the circuit for a couple of hours today, because my unit was unstable with larger coil for unknown reason.
After a session with scope, I added two 1µF tantalum capacitors between ground and +5/-5V, very close to US2 (I even thought about soldering them directly to the US2, but it's easy to damage IC that way).
Then I found out that the GND carries spikes (couple of mV's) caused by the coil current. I desoldered the coil ground connection from the point marked on PCB (take look at the ground path, IMO it's a design flaw) and soldered it directly to the C12, it reduced the noise by a lot and the detector runs stable

[pelanj]

I have not opened the detector since my last post, I still need to get all the parts. I have tried some new coils, but I need to get a proper cable and get rid of the cinch. Some cheap connectors kept my coils beeping all the time. I was even thinking of using a pigtail and some sort of "WAGO" terminals instead of a connector.

I also bought some PVC pipe to play with - how do you put the parts together? I could not put a knee or a T on the pipe without cutting down the edge or heating up by a flame. Is there an easier way?

[Pepe LeMiau]

For my second coil I used 2x2.5mm^2 flat cable bought in audio store, it's the cable used to connect speakers to amplifier. It is relatively cheap (I bought 3 meters at about 12PLN here [about $4]) elastic and strong (the insulation is thick), also it's resistance is low and that's important.

The chinch is totally unreliable, I still had it last time I went out with the detector and it already caused minor problems (false signals) even though it's almost unused. For now I soldered the coil to the PCB, however I'll probably go to junkyard to search for industrial connectors, there are always plenty of old machines to search in. Last time I found these heavy-duty BNC-like sockets [18mm diameter], unfortunately I didn't find plugs



The pipes I used just fit inside the "knees" or "T" connectors without too much force. That's why I like them, the "T" with two short pipes makes a very nice variable angle coil mount
I cut my shaft into 3 pieces, drilled holes through all pipe-to-pipe connections and put there M5x60 screws (the one near the coil is M6x60 nylon) to hold everything in one piece.

http://img534.imageshack.us/img534/1189/schl.png

[der_fisherman]

The plugs and sockets you are looking for are probably German UHF plugs of the 2nd World War, often used on CB antennas nowadays.
Check thse links out:-

http://www.produktinfo.conrad.com/da...hse_UG_266.pdf

http://www.conrad.de/ce/de/product/7...266U/?ref=reco

http://www.conrad.de/ce/de/product/7...-259/?ref=reco

http://www.produktinfo.conrad.com/da...KER_PL_259.pdf

These are quite big, but VERY stable connectors for coax cables.

I hope this helps (better late than never!)

Andy

[der_fisherman]

For my second coil I used 2x2.5mm^2 flat cable bought in audio store, it's the cable used to connect speakers to amplifier. It is relatively cheap (I bought 3 meters at about 12PLN here [about $4]) elastic and strong (the insulation is thick), also it's resistance is low and that's important.

The chinch is totally unreliable, I still had it last time I went out with the detector and it already caused minor problems (false signals) even though it's almost unused. For now I soldered the coil to the PCB, however I'll probably go to junkyard to search for industrial connectors, there are always plenty of old machines to search in. Last time I found these heavy-duty BNC-like sockets [18mm diameter], unfortunately I didn't find plugs



The pipes I used just fit inside the "knees" or "T" connectors without too much force. That's why I like them, the "T" with two short pipes makes a very nice variable angle coil mount
I cut my shaft into 3 pieces, drilled holes through all pipe-to-pipe connections and put there M5x60 screws (the one near the coil is M6x60 nylon) to hold everything in one piece.

http://img534.imageshack.us/img534/1189/schl.png

The connectors look like German DIN plugs, called HF here and still used on citizens band radio aerials.....big and high quality.

[martinBMW]

Hi dantech, please can you give here pcb layout? Thank you very much.