My Pulse Oscillation detector project.

[Tec]

Hi,

I am interested in this. I am working on a similar design.

It has good FE discrimination.

There is frequency shift due to a metal target.
I believe this is no different to the frequency shift in a PI pulse, or the frequency (not phase) shift in a 'Induction Balance' detector.

All these technologies do the same thing to a target: Present a changing magnetic field.

The good thing about a free-running oscillator like this is that the tiny shift in each cycle adds-up (compounds) over time, so if you measure over say 1000 pulses, you get a decent measurable change.

Another excellent thing is that power is not wasted in a resistor, it is re-used (i.e resonating)

I believe this style of detector can be more sensitive than any other technology.


I think:
To decrease the sensitivity to high resistance targets (wet sand and ferrite) : decrease the frequency.

[TekJosec]

I am currently working at it, to add this feature. Current plan is to make some kind of dual tone sound, so that Ferro NonFerro will make different sounds. I want it to sound something like old times PC speaker music. The information to distinguish is already there, just need to program new sound system.

Struggling with sound algorithm. I guess I will try to make dual tone sound by switching periodically between audio frequencies. Keep one frequency constant, alter other frequency depending on target.

Any ideas welcome! If anyone knows a good page about how pc speaker sound was generated for old games, please post link here!

And why not upgrade the project to another PIC and put a LCD display , headphones output and many other things...
I could help!! my problem is the assembly language, i only program mplab on C language.

Seems a very nice project and waiting for parts to test. About the range of the detector it must be worked (find the better coil project), the entire structure construction (wood, PVC).

[6666]

Hi Teemo
I had a bit of success and good start to your project
output from pin 2, programmed with Pickit3 and MPLAB IDE 8.76

[bernte_one]

hello
i search for some replacements of IRL630
which is the best one?

	Polarity	Struct	Pd	Uds		Ugs	Id	Tj	Fr	Cd	Rds		Caps
1.	2SK1221	N	MOSFET	80	250		30	10	150			0.4		TO220AB
2.	2SK1761	N	MOSFET	75	250			12				0.23		TO220AB
3.	2SK2841	N	MOSFET	80	400			10						TO220AB
4.	2SK2866	N	MOSFET	125	600			10						TO220AB
5.	2SK900	N	MOSFET	80	250		20	12	150		1800	0.3		TO220AB
6.	AUIRFB4127	N	MOSFET	375	200		20	76				0.02		TO220AB
7.	AUIRFB4227	N	MOSFET	190	200			65				0.026		TO220AB
8.	AUIRFB4332	N	MOSFET	390	250		30	60				0.033		TO220AB
9.	AUIRFB4620	N	MOSFET	144	200		20	25				0.0725		TO220AB
10.	HIRF630	N	MOSFET	74	200		30	9	150	28	240	0.4		TO220AB
11.	IRF630N	N	MOSFET	82	200		20	9.5				0.3		TO220AB
12.	IRF640N	N	MOSFET	150	200		20	18				0.15		TO220AB
13.	IRF644	N	MOSFET	125	250		10	14	150			0.28		TO220AB
14.	IRFB23N20D	N	MOSFET	170	200		30	24				0.1		TO220AB
15.	IRFB260N	N	MOSFET	380	200		20	56				0.04		TO220AB
16.	IRFB31N20D	N	MOSFET	200	200		30	31				0.082		TO220AB
17.	IRFB38N20D	N	MOSFET	320	200		30	44				0.054		TO220AB
18.	IRFB4020	N	MOSFET	100	200		20	18				0.1		TO220AB
19.	IRFB4127	N	MOSFET	375	200		20	76				0.02		TO220AB
20.	IRFB4227	N	MOSFET	190	200		30	65				0.026		TO220AB
21.	IRFB4229	N	MOSFET	330	250		30	46				0.046		TO220AB
22.	IRFB4233	N	MOSFET	370	230		30	56				0.037		TO220AB
23.	IRFB42N20D	N	MOSFET	300	200		30	42.6				0.055		TO220AB
24.	IRFB4332	N	MOSFET	390	250		30	60				0.033		TO220AB
25.	IRFB4620	N	MOSFET	144	200		20	25				0.0725		TO220AB
26.	IRFB5620	N	MOSFET	144	200		20	25				0.0725		TO220AB
27.	IRL630	N	MOSFET	74	200		4.5	9.0	150			0.4		TO220AB
28.	IRL640	N	MOSFET	125	200		4.5	17	150			0.18		TO220AB
29.	KF13N50P	N	MOSFET	208	500		30	13	150	45	210	0.35		TO220AB
30.	KF9N25P	N	MOSFET	83	250		30	9	150	25	96	0.31		TO220AB
31.	KHB019N20P1	N	MOSFET	140	200		30	19	150	33	80	0.14		TO220AB
32.	KHB9D5N20P	N	MOSFET	87	200		30	9.5	150	62	96	0.345		TO220AB
33.	PHP20NQ20T	N	MOSFET	150	200			20				0.13		TO220AB
34.	PHP33NQ20T	N	MOSFET	230	200			32.7				0.077		TO220AB
35.	PSMN057-200P	N	MOSFET	250	200			39				0.057		TO220AB
36.	PSMN070-200P	N	MOSFET	250	200			35				0.07		TO220AB
37.	TK13E25D	N	MOSFET	102	250			13				0.25		SC46/TO220AB

Über 37 Ergebnisse

[Waikiki_Sweep]

IRL630

L = Logic level gate voltages. With "IRL" MOSFETs you can drive it straight from the microprocessor.
For other MOSFETs you will need to add to schematic MOSFET driver IC or transistor (transistors).

[Waikiki_Sweep]

As you can see IRL630 can drive several Amperes (ID) with less then 5 Volts on gate (Vgs). It is not so easy to find a replacement.

[Teemo]

For IRL630 replacements the priority parameters are:
-Gate treshold voltage(Vgs): must be less than 4,5V (often called "logic level mosfet")
-Drain source voltage Vds: must be 200V

Other project news:
I have done some testing with the audio, managed to program the variable volume and tone using available resources. Only modification to schematic:It is clear that piezo speaker will not do, instead there will be dynamic speaker or headphones. New sound will use 8 or 10 bit PWM, not clear jet how the modulation will be. I guess the fancy circular buffers from the current version is not good for the new version -- the new algorithm must be simpler. To get the direct unbuffered information from the coil to the headphones/speaker.
And thanks all who participate in here forums. The tips I get here are most useful, even if I can't grasp all the ideas promptly.

[bernte_one]

ok
thanks for reply
i have choosen irl640
and some testing replacements for elko 1000 -3300uf 10-16V, the 1uf and the 47nf cap
will post results asap

kind regards
special thanks to teemo

[bernte_one]

detector is alive

i used a ferrite core inductivity around 340µH (desoldered from some scrab electronics)
i think it should work fine as pinpointer
now i search for the smallest 5V power source so that all fits an a small tube enclosure
and i will make a better ferrite-coil

would say it is the best beginners project in category microcontroller/pinpointer

kind regards

[Waikiki_Sweep]

now i search for the smallest 5V power source so that all fits an a small tube enclosure

I am not sure will it work from 3.7V (charged 4.2V) 18650 Li-Ion battery. If yes it will be absolutely great because it is compact, rechargeable, lightweight and very powerful 3000-4000 mA/h!

I am using 3 cells starting at full charge 4.2 Volts (12.6 V) and discharging to 3.9 Volts (11.7 V) after 10 hours of work of my overclocked to 130 mA Surf PI.

At least microprocessor will work.
Operating Voltage Range:
- 2.3V-5.5V (PIC12F1840)
- 1.8V-3.6V (PIC12LF1840)

The problem is IRL640 will work from 4 volts or not also maybe some adjustments are required to software and / or electronic.

[bernte_one]

i think about 18650 bacause i had a lot of them
but the have a critical voltage max 4.2 is not enough
so my favourite is a small akku pack of 4*1,2V aaa nimh (eneloop?)
and a simple charger plug with max charge of 5V usb or micro usb??? - modern standard

what do you think?

[bernte_one]

hello teemo

can you give me some advice to increase the detection range
at the momnt i can get maybe 4cm on a 2€ coin with a pinpointer coil (16mm diameter, 5cm long, litzwire with ferrite core around 80µH)
the sound range (from little noise till full sound) is very small maybe 5mm range
is it possible to inrease this threshold sound range? a litle bit more noise is no problem if i get two more centimeters of range

at which parts should i focus my work?

will post a picture later

kind regards

[Teemo]

hello teemo

can you give me some advice to increase the detection range
at the momnt i can get maybe 4cm on a 2€ coin with a pinpointer coil (16mm diameter, 5cm long, litzwire with ferrite core around 80µH)
the sound range (from little noise till full sound) is very small maybe 5mm range
is it possible to inrease this threshold sound range? a litle bit more noise is no problem if i get two more centimeters of range

at which parts should i focus my work?
will post a picture later
kind regards

Hello
The solution that comes to mind first is to modify the firmware PIC program. As you very well describe it should be possible to get some more range when to allow some more noise.
I've also have had this in mind. The current firmware is very well optimized to my original objective of scanning logs, the digital filtering allows very few noise.
This requires quite big modifications to the firmware. Basically the digital filters must be redesigned. In the assembler program there are variables f_result and t_result those are the basic measurements that are passed to the filters in the main program.

Best regards and thanks.

[bernte_one]

hello teemo
i have to make some experiments with the source code
but for the moment lokk what i have done (only prototype)
http://www.youtube.com/watch?v=9eG3-gmh7tA

if i get more depth by changing the code i will send you the changes if have done
and i will post a link on my video to your shop side if that would be ok for you?

my goal is to get 2cm for a small nugget and around 8cm for a 2€ coin
will see

kind regards

[Teemo]

Hello bernte_one

Thank you for the video.
Wery interesting construction. Nice to see.
I will gladly examine the code changes if you send to me, and of cource I will be happy when you put link to my site in your video.

Best regards