Cable for MPP mono coil - CB coax good enough?

[Qiaozhi]

Umm, so when you say just 2 wires travelling from coil up to the box you mean one of these is connected to the sheild I am wrapping around the coil I made. What is the second wire? I have the 2 ends of my coil ----- are you saying therefore I connect these together at the coil end and connect to the 2nd wire ??

Assuming the upper plug layout in fig 14 is at the box end then this sugests I send down to the coil THREE wires ie one to the shield and one to each end of my single coil?

I think I am not understanding something here and I can hear you lot saying -- its obvious!!

Please educate me further!!

Cheers

John

John - you are obviously horribly confused about this, but the connections are really quite simple. If you connect the two wires of the coil together (either at the coil or at the plug) then you've essentially shorted it out. How do you think any current will be able to flow in the coil?

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John,

Connect one coil wire to 1(receive), the other coil wire to 3 (screen), and the shield to 3 (screen), and jumper 1 to 5 at the connector as in fig 14.

The connection method described above by baum7154 will work for your coil. Just connect it that way, and everything will be ok.

The MPP is designed to use either a mono or a balanced coil, and that's why there are two connectors on the PCB. One for transmit (TX) and one for receive (RX). If you are using a mono coil (i.e. a coil that is used for both TX and RX) then you need to short pins 1 and 5 at the coil plug. Otherwise you will only be transmitting and not receiving.

I suspect you are another member who has little experience in electronics, and building a metal detector is not necessarily a good choice for a learning platform ... especially when it doesn't work quite right, or even not at all, and you end with an expensive brick.

You would no doubt benefit from obtaining a copy of Inside the METAL DETECTOR - Second Edition - Published 2015

[JOHNCGRAY]

Thanks for all your help- yes I am knew to this although chemical engineer with experience repairing scientific instruments at board level, the theory behind all this is all new to me and at my age it takes longer for me to grasp stuff! I m reading lots so I am trying. It was just that pin 1-5 bridge that was throwing me I suppose as I could see how a flow around the coil and back again could be acheived..

Thanks again for all your help and patience

John

[6666]

Fig 14 shows you how to connect the coax to a mono coil.

Coaxial cable has an inner conductor and a outer conductor, the outer conductor is usually a woven copper braid that acts as a screen or shield that is connected to ground.

Try and avoid the cheap coax that only uses foil and a few strands of copper wire as the screen/shield and a solid wire as an inner conductor that will flex and break.
a cable with a woven shield and a multi strand inner conductor can with stand a lot of flexing.

When you wind your coil there will be two ends to it.

At the coil end you connect the inner conductor to ONE wire only

you connect the other coil wire to the screen/shield of the cable AND to the foil screen you have wrapped around the coil

Now at the PCB end , looking at fig 14 carefully you need to install an insulated wire from pin 2 of plug 2 to pin 2 of plug 4
that is shown as the red/green wires.

Now solder the inner conductor of the coax on pin 2 of plug 2, and the outer conductor screen/shield of the coax to pin 3 of plug 2
easy peasy.

[JOHNCGRAY]

Got it!
Thanks for your time and help, much appreciated.
John

[geoscash1]

Here is a simpler diagram

[JOHNCGRAY]

Here is a simpler diagram
[ATTACH]39194[/ATTACH]

Nice - totally understood now. I was missing one piece of info - connecting one end of my coil to the shield. Without this I got hideously confused with fig14. All clear now and the Administrator was perfectly correct in pointing me to study more and solder less at this stage! Point taken.

John

[digga]

is the diagrahm 14 a std way for a minelab coil to plug in or will it be diffrent

[homefire]

RCA Video Cable works fine for most Mono Coils. RCA Connectors are handy.