my hammerhead PI

[lbt]

hello

i build a hammerhead PI from CARL design (non VCO option)With a PIC 18f452 for all the timing (freq TX,delay,sample...) a lcd module for timing control . I want to say that the hammerhead work very well . i have a coil 27 turn dia 20cm and i can detect 2euros at 25~30cm minimun in air (outdoor) and a popcan at 65~70cm .

i do some littles modifications for the schematic:

-for the mosfet command i give r4.7K to ground in order to reduce VGS and reduce the gate capacitie
- for all the CI i take a 100nF capacitor between +5V/Ground and -5V/ground in their alimentation.It would be better than 100nF between +5V/-5V.

Thank you CARL for your detector and excuse me for my BAD english(i'm french!!)

[kt315]

hi lbt,

I did read similar post to your experience with to exchange a part on the chip.
I still keep this. can you share photos of your construction? give a programming code a free? give the schematic? did you make 2 samples processing on the chip?
tia.

Posted by Dan Golden
Wednesday 12 May 2004, 11:18:53
In Reply to EE Treasure Hunter - Posted by arjoca mihai on 5/12/04

The PIC 16F84 is a better choice as you can keep reprogramming it since it is a "flash" version. I gave up on Stuart's PI and made Gary's PI detector. It detects a 1 ounce coin at about 30 inches w/ a 15 inch coil. I converted it to be controlled by a PIC 12F675 (8 pin DIP) and it works great. Got rid of all the 555s. I made a new 24 inch coil and it detects a small tin can at 3 feet quite easily in air. I'd recommend you switch to the 12F675. They are less expensive (~$2 from Jameco) plus it has a comparator that you can put on the output instead of the 555's noise maker. I am using 2 12F675s, one on front end to drive coil and timing for collection and one on output to drive headphones. Works great! I still get best detection distance using a meter however.

[lbt]

i make photos of my PI this week.
The PIC make the timing: TX freq, TX width, sample1 delay, sample2 delay,sample width.The 7660 in free run. I finish the schematic and i give him in the forum later.
On the circuit boardyou can program the PIC (ISP) with ICPROG or another soft.
The programme is build with MPLAB(microchip).