The Crossbow Classic PI

[Qiaozhi]

this was my crossbow before i put it on to a straight shaft.

Click on Reply, then click on Go Advanced.
Scroll down to where it says Manage Attachments.

[Qiaozhi]

If I do consider a mono coil, do I check that it has a specification of: Inductance 500uH and Resistance 2ohms with a built in damping resistor? I guess that the connections inside its 5 pin connector (if it has one of 5 pin) will have to be altered as per previous info’ provided by George?

The original 10" diameter coils have a built-in damping resistor, but commercial coils will have this resistor located externally. You can also use these coils on the CCPI by adding a suitable resistor inside the enclosure at the back of the coil connector socket. The socket should have 5 pins, but only 3 of these are in use. Pin 1 is TX, and pin5 is RX. The shield (0V) is connected to pin 3. This means that pins 2 and 4 are available. For a mono coil (like the standard one) pins 1 and 5 are connected together, and the shield goes to pin 3. For the Garrett Seahunter coils, I put the resistor across pins 2 and 4, and then (in the coil plug) jumpered pin 3 to pin 4, and pin 2 to pin 1, with pins 1 and 2 shorted together, and the shield connected to pin 3. Alternatively you could provide the facility for the two different values of damping resistor, by connecting one resistor between pins 2 and 3, and the other between pins 4 and 3. Then add jumpers in the coil plug as appropriate. I haven't tried using a Minelab coil, but I believe the coil plug is the same as the CCPI, and may even have the same wiring. Although you'll have to check that yourself.

For a coil with separate TX and RX windings, you must not short pins 2 and 4 together (obviously).

I have seen drawings comparing the signal shape in the ground between the two types of coil, will the shape remain the same with a DD coil on a PI machine?

Yes.

I note that DD coils seem to be made for individual detectors, e.g. a coil for a Minelab Sovereign wont work on a Minelab Explorer. So how do I find a DD coil for the Crossbow? What specifications do I need to find or ask a manufacturer for?

The inductance can be between 300uH and 500uH. The coil resistance is not that important.
If you post details of the coils you're considering, I'll can let you know if it will work.

Will the 5 pin connector connections need to be altered?

Yes - see above.

Oh, almost forgot….How do I tell when it is fully charged?
Thank you.

Just charge it for the recommended time. The built-in charger is current limited, and it will go into trickle-charge mode once the batteries are charged. I've left them on charge overnight without any problems.

[keith777]

unreadable pics K777.

are my pictures not showing or something like that.

[Qiaozhi]

are my pictures not showing or something like that.

They're not showing. You've probably linked them to images on your own computer, which no-one else can see.
See post #31 for details of how to upload pictures to the forum.

[kt315]

are my pictures not showing or something like that.

english is not my native K777. why i can that you can't... all around you here in english...
you are in YOUR native environment here... i do not have to learn you.

[keith777]

i could see my photos yesterday when i made the post. some how they are not showing now. never mind i will re-post again.

[keith777]

this was my crossbow before i put it on to a straight shaft.

photos re-added.

[Qiaozhi]

photos re-added.

Thanks for re-posting the photos.
This is not an original Crossbow Classic unit. It's a clone produced using an PCB design I sent to Sven.
The original had a battery check LED on the front panel, and you can see that's missing here. Also, the enclosure and the coil are different.

[keith777]

so the crossbow that i have. does anyone know how many of them have been made?
also is mine any deter in any way than the original one. has anyone compared the two?

[keith777]

oops. typo in original post.

so the crossbow that i have. does anyone know how many of them have been made?
also is mine any better in any way than the original one. has anyone compared the two?

[Qiaozhi]

oops. typo in original post.

so the crossbow that i have. does anyone know how many of them have been made?
also is mine any better in any way than the original one. has anyone compared the two?

Since it's based on a PCB design I sent to Sven, it should have the same performance as the original. I've no idea how many clones have been produced, maybe Sven knows. I don't think there were many, as it's quite a complex design for many people to duplicate.

From the eBay photos, it looks like the battery pack was replaced by a larger capacity Li-ion type, and there were some other quite minor modifications.

[TowySalmon]

Thank you so much Qiaozhi. Your reply is very helpful and at this moment just beyond some of my brain cell capabilities, but I do get the gist of what you say and has given me hope for an alternative coil that wont be impossible to achieve.

I must admit that I have used Coiltek WOT DD coils for Minelab Sovereigns for many years (14"/15" diameter depending on whose ruler is used haha) and like them very much indeed. I also like the RIF DD coil too of similar size. I do not have a spare Coiltek coil, but I do have a RIF coil for a Minelab Explorer gathering dust at the moment and it is looking lonely in the corner of the bedroom. If that could be utilized, that would be fantastic. Alternatively, I do not mind buying a new or second hand Coiltek WOT DD coil.

Please appreciate I have no soldering skills and no technical skills, someone will need to help me, but I have made 3 headphones for detectors...not one of them matches any other-all three are wired differently, but heyho, they work.

Really looking forward to next installment now.
Thanks again.
PS Keith, nice pictures. My control box is above armcuff. I do not have enough skill here yet to upload pictures, so well done and thank you on showing us your setup.
PPS this looks good and is lighter than the Cors coil http://en.marsmd.com/catalog/mars-md-goliath/
PPPS. I have seen this coil and like the look of it and it is waterproof: http://corscoils.com/index.php/product/fire

[Qiaozhi]

Thank you so much Qiaozhi. Your reply is very helpful and at this moment just beyond some of my brain cell capabilities, but I do get the gist of what you say and has given me hope for an alternative coil that wont be impossible to achieve.

The coil you choose needs to be intended for a PI detector. Coils for VLF detectors will not be suitable.

[TowySalmon]

Thank you for quick reply.
Now I have no idea what to say.
I am happy to pay for new DD coil for this detector and to change the coil connections and add resistors etc.
But now I just do not know what to say.
All I want to do is add a DD coil. Please can you suggest one that is 15" diameter?
Thank you

[keith777]

a 15" or bigger coil sounds good to me.........