PICKINI V4 - an easy to build, self adjusting PI detector

[SaltyDog]

Thanks for the replies.

It seems from the graph I posted, that to reliably detect non-ferrous, you need the pre-amp to come out of saturation within 4us, that means a fast op-amp, which the LM318 is, and also a fast coil. I think with a basket weave coil or a spider weave coil with Litz wire (or equivalent) is the only option to get discrimination ..

If you don't have all those ducks in a row, it won't be reliable ..

My 2c.

[6666]

Hi Bernard,

I am thinking, without too many modifications, it is possible to do simple two tone discrimination, by just some simple code changes (as per the White's PI)

If you have a look at the attached image, it shows the pulse decay for different metals (ferrous, non-ferrous). If you judiciously choose the slice level (i.e maybe some manual control), then you would get the pulse width "decreasing" for non-ferrous.
(i.e if you put a line at 0.3v on the graph, then non-ferrous would give you 5us, no target 7us, and ferrous 12us .. as an example)

If you map that to a different tone (and/or light) we could get some form of discrimination ..

Let me know what your thoughts are ... I could have a go at the code changes to try it out ...

You would of course need a fast coil ..

[ATTACH]49654[/ATTACH]

Invalid Attachment specified.

[SaltyDog]

Invalid Attachment specified.

I don't see any text, what are you saying? I only see "Invalid Attachment specified"

[6666]

I don't see any text, what are you saying? I only see "Invalid Attachment specified"

click your attachment

[SaltyDog]

Oh, I don't see why it is invalid .. it worked when I clicked it when 1st posted, don't know why it is invalid now .. it's just a .png file

Mind you, I have cliked on a number of attachements from other users and I get that message too .. is the forum having issues?

I will try again ...

[IBGold]

Oh, I don't see why it is invalid .. it worked when I clicked it when 1st posted, don't know why it is invalid now .. it's just a .png file

Mind you, I have cliked on a number of attachements from other users and I get that message too .. is the forum having issues?

I will try again ...

[ATTACH]49655[/ATTACH]

That works now.

Regards, Ian.

[6666]

Strange if you click the attachment in post #16 it says invalid , but if you click the quoted text in Ibgold's post it shows the graphic

[SaltyDog]

Yep, something weird going on with the forum me thinks .. maybe an administrator should chime in?

[Qiaozhi]

Yep, something weird going on with the forum me thinks .. maybe an administrator should chime in?

There's no problem with the forum. You must have attached it incorrectly.
Sometimes people add a link to a file that's on their personal computer, rather than uploading it in the correct manner. Then, of course, no-one else can see it except themselves. Another reason for attachments going AWOL, is when the link points to a file elsewhere on the internet, and that file has been deleted.

[bernte_one]

i have no luck - some of the latest pickini i did last years will not work exactly
i got very similar problems on the 4 boards laying on my work bench
look the voltage diagram, pin 5 of lm318 has one very bad voltage can that be a result of bad bs170??

also pin 2,3, and 6 seems a bit off the tolerance

voltage from the pic controller looks also not ideal

Pic16F1824
Pin	normal from f117	my result with coil	without coil
1	5	5,02	5,02
2	2,7	3,18	3,18
3	1,2	2,76	2,76
4	5	5,02	5,02
5	4,7	4,7	4,7
6	0,1	0	0,3
7	0	0	0
8	3,7	4,22	4,38
9	3,7	4,21	4,38
10	2,7	3,17	3,17
11	0-5	2,5	5,02
12	2,8	2,75	2,73
13	2	1,52	1,52
14	0	0	0
LM318	normal from f117	my result with coil	without coil
1	9,5	9,25	9,17
2	6,8	8,3	8,23
3	6,8	8,3	8,26
4	0	0	0
5	4,8	9,28	9,2
6	7,4	8,4	8,82
7	11,9	11,76	11,76
8	1,4	1,3	1,32

[bernte_one]

or problem with bc549B?


ok i got some answer in
post 227 and 228
same problem
https://www.geotech1.com/forums/show...290#post224290

how can i disbale mclr whule programming with mplab and pickit3?

[F117]

You describe 2 different problems:
1/

how can i disbale mclr whule programming with mplab and pickit3?

If you have this problem, the controller should reset when you activate the pinpoint switch = MCLR low.
Then you should hear the welcome sound again.
As long as you don't push the pinpoint switch, this should not do anything, everything should start up and work normally.

2/ A problem with the DC offset of the opamp:
Pin 3 of the opamp is the DC offset that gets adjusted after startup.
Pin 5 of the opamp is not connected. The BS170 is not related to this. The BS170 is just a level converter that transforms the 5V pulses to 12V to the gate of the IRF740.

Do you get the coil error sound after calibration = continuous low tone ? This indicates that there are no flyback pulses at the input of the microcontroller.

I don't see a problem with the BC547: VBE = 0.6V.
But the collector voltage in your drawing is 6.15V. this should be equal to the voltage on pin 3 of the opamp, which is 8.3V in your case. In between the collector and the opamp pin 3 there are only 2x 10 ohm resistors in series = jumpers on the PCB.

[bernte_one]

OK
1 is all right, Pinpoint works as it should

2 after start i get OK sound after 10sec or so, then the detector start to Chatter.
I can still detect but only very Close to coil.

Coil is 300microH Made from 0.6 Wire 19turn 35cm Dia, so nearly perfect

Earlier today i tried to adjust damping resistor.
I found out that 500r like basic Setup ist too low, at 620r the damping curve is smooother, but detection distance ist very bad.
I suppose the trouble are result od BC549 and LM318 (Offset, etc.)

[F117]

Sounds normal .... chatter is typical when you switch on the detector inside the house.
Try to move it away from any EMI sources.

[SaltyDog]

There's no problem with the forum. You must have attached it incorrectly.
Sometimes people add a link to a file that's on their personal computer, rather than uploading it in the correct manner. Then, of course, no-one else can see it except themselves. Another reason for attachments going AWOL, is when the link points to a file elsewhere on the internet, and that file has been deleted.

Ok, but when I hit the "Insert Image" button, it prompts me for a file on my computer !!!! So what have i done wrong ? I am just doing what I am told ..