Hammerhead Rev D discussions

[Ray-NM]

New TI cmos switch

http://focus.ti.com/lit/ds/symlink/ts12a4514.pdf
A new switch from TI that has lower on resistance.
Raynm

[Ray-NM]

4066

In the past I have noticed what I thought was noise on the ouput of the preamp and could not figure where it came from. Well I was reading the spec's on the 4066 and found something I had not noticed before. I tend to look at something such as this for a long time before the obvious slaps me in the face. Anyway the 4066 looks like it will send signals backwards just as well as forward so thats where my unexplained noise was coming from.
What I am talking about is a small noise spike that does not show up until you set the main delay to the right spot and then you see it back on the ouput of the preamp. Just thought I would share with you what is probably obvious to most. You learn something everyday.
RayNM

thanks! But the link shows the placement, if I want to etch my own PCB I need a raw layout without any printed parts. Or am I wrong?

Thanks again

[Reg]

Hi,

You can go to the top of this page, click on Geotech, then click on Hammerhead project and then scroll down to Rev D.

Here is a link to where you will end up.

http://geotech.thunting.com/pages/me...rhead/HHd1.pdf

Reg

Where can I download the through hole layout for Rev. D??

[Buzz(ID)]

HI Reg
I had some other projects pressing, been busy for a while, I haven't finished
the HH project yet , I am still on the learning curve and got a ways to go ,taking it slow , nice to hear from you though its been a while. I do need the external components you mentioned and will probably use another Pelican case 1050, I am still looking for a decent O scope .


Buzz

[Wirechief]

Hi Carl, just to let you know I got my boards in today and many thanks to you. God Bless and happy hunting!

John Tomlinson,CET
John's Detectors
Blackwell,Tx.
www.johnsmetaldetectors.com

[Carl-NC]

Q12 is off until the base voltage is ~ 0.5-0.6V above the emitter (-5V). This occurs when the battery reaches ~ 10.5V. When Q12 turns on, its collector current is pulled from the base of Q13 and gets beta-multiplied, so Q12/Q13 form a Darlington pair.

I don't remember why I chose the values for R52/R53. R52 could probably go a little higher, maybe to 27k-30k, to set the low indication closer to 9.0-9.5V, which should still work fine.

- Carl

[1843]

Battery Indicator

Hi Carl,

Would you please explain how does the HH battery indicator work?

Thanks in advance

[Carl-NC]

What happens when you put it in a box/casing, how are you going to adjust the trimpots, should not there be a few potentiometers connected there somwhere??....understandable, as the instructions/bill of materials isn`t really clear on that point.

I intentionally left out all these details, because there are so many options. Whatever externally-accessible adjustments you want to have, you can have. Whatever enclusure you want to put it in, you can. Whatever coil form or shell you want to use, you can.

- Carl

[Reg]

Hi Buz,

How in the heck are you?

What you need to decide is which controls you want to adjust from the outside and then remove the internal pots, add headers or simply jumpers to go to the external controls.

I have more external controls than necessary, but the basics I feel you need are the threshold, the autotune speed, the pulse rate, the delay, and maybe a gain control. Some people not trying to use the detector for gold hunting can leave the autotune speed control internal and not make it an external control.

Reg

I hope all of the componets are correct?


Buzz

What happens when you put it in a box/casing, how are you going to adjust the trimpots, should not there be a few potentiometers connected there somwhere??....understandable, as the instructions/bill of materials isn`t really clear on that point.

[Carl-NC]

Same thing as in Rev C... it drives the chopper switch IC7c to produce an audio signal. Only used for non-VCO option. It looks a little different in Rev D because I moved it to the output of IC9.

- Carl

What does Q10 do in the rev D of Hammerhead?

Thanks

[1843]

OK!

Thanks Carl,
You are right.
Cheers