PI Project

[Carl]

OK, finally... here is the schematic, PCB, and parts placement for the PI design. Yes, I know, the PI schematic does not make much sense, what with all the jumpers. I will post simplified versions with extraneous parts removed, ASAP. Please note the resolution of the PCB... if you print it on a 300dpi printer you will need to scale the image by 50% first.

Schematic - 300 dpi GIF (174K)
PCB - 600 dpi GIF (258K)
Parts placement - 300 dpi GIF (178K)

[Darta]

Re: PI Project

I'am interest of timing description of circuit for TECH
______________________Value________________Descrip .

1.-Mosfet_On---------------T1=50us-100us?_______Power_Coil
2.-Mosfet off----------------T2/T3=aprox?_________Reverse Power
3. Pause?--------------------T3 aprox?____________ Nothing
4. Invert integrator-----------T4/T5?_______________ very interest! Compensated Ground
4.Integration-----------------T5=
.
.__________________________________________ Comparator/Sound
.
10. Mosfet On-------------- T10
11. Mosfet off---------------T12
12. Pause?------------------T13
13. NonInvert integrator-----T14__________________¡Its correct?
14.Integrati{on------------- T15


Sorry for my poor Inglish! !!!!

Thank You / Gracias

[Russ_NY]

Re: PI Project( Thanks Carl)

Very Good Carl Thanks,
Unfortunately my best scope has developed a focus problem, and I can't find the service manual. I have it, just can't lay my hands on it. I really am anxious to look over your latest revision, but I think some serious houskeeping is going to be the order of the day till I find the missing manual.
Thanks Again
Russ

[Al Arens]

Re: PI Project

What is the actual size of the pcb?

[Carl]

3.5 x 4.0 inches n/t

.

[Carl]

Re: PI Project

Not quite sure what all you're looking for. I am working on an explanatory article, I'll try to get a preliminary version posted ASAP. It will cover some of the timing ranges.

- Carl

[Gustaw]

Re: PI Project

Hi Carl,
It thanks for publication diagram of the metal detector. I ask, of graphs in measure points (TP), is possible me about or message as well as in building of coil - diameter of wire - diameter of coils, arrangements of jumpers.
Did you try coils about dimensions 1 x 2 metre?
I'm sorry my English.
Help my. Thank you very much, Good luck.
Gustaw

[Robert Hoolko]

Bandwidth

Carl

I don't know what all the compensation on the amplifier does, but the main feedback seems to have a 15 usec TC. That is longer than I expected. Is this typical of PI's? I thought they had wider bandwidth than that. This may change my opinion about sampling and noise.

I thought they were about 100 kHz.

Robert

[Carl]

Re: Bandwidth

The main feedback cap was thrown in for experimentation. I am not currently using it, and most designs I've seen do not, either. The rest of the compensation mess is to accomodate different opamps.

- Carl

[Carl]

Re: PI Project

OK, yes, I plan to make waveform plots of the test points, as soon as I have time to write up some instructions.

The coils I wound are 28 AWG, which is smaller than I wanted... I'd recommend 24 AWG. I wound 150mm (40 turns), 200mm (30 turns), and 250mm (24 turns). So far, just testing with the 200mm. I have not tried any meter-sized coils.

- Carl

[Gustaw]

Re: PI Project

Hi,
Thanks very much for answer.
Probe "coil" 1 x 1 m AWG 20 ... 24 (8 turns).
I ask plan to make waveform plots.
Thank you very much.
Good luck
Gustaw

[Viktor]

Re: PI Project

Hello Carl!

Please, tell me about Q4, IC9 (7 pin).
I don't understand about jumpers or tumblers ?
Have you a photo (image) of detector or pcb with IC.

Sorry for my bad English.

With best regards Viktor