Can pinpointer detecting thin chain?

[Polymer]

I give up. Two years ago I tried to make pp and it did not work. Now I have repeated the circuit in a perforated plate connecting everything as shown in the diagram and it does not work either. The only difference is c1 is mkt, I can not find it in mkp. Even if c1 mkt pp should give some signal? My pp is totally silent.

Just tried a 2.5% 1500pF Wima 100V capacitor for C1 which I found in my junk box. It works! It is red with a yellow filling, I don't know if it's MKP or MKP2 or ???

[chemelec]

I just used Polyester Caps.
And a Slightly Modified Circuit, Works Good.
(My Ferrite Rod is just a 1.5 inch Long and 1/4 inch Diameter.)

[Virdi_248]

Like Ionut is saying try a bigger pot first. I understand your frustration, had that too. Wanted to smack it with a big hammer.

I use an approx. 70k fixed resistor in series with a 50k multiturn trimpot in series with a 2k multiturn trimpot (for fine tune).
Are you driving the speaker or LED directly from the 4024? For me this did not work well at all.

Is your coil wound correctly and have you connected it the right way around? Have you checked the voltages? Is your transistor in the right way?
My 3906 & BC560 have different CBE-EBC, so that could be a problem.

I am not sure about the 1.5nF capacitor. I will see if I have one and try it and post the result.

Could you put a photo in here? Good luck!

Thank you.
It is the second time and this time I have taken special care in everything. I have remarked normal nupi with bc560 and bd139 fixing me to place them correctly, without motor.
I also checked the track with multimeter and everything ok.
I will change the two potentiometers to 100k and I will buy the capacitor 1500pf mkp 1500v (22 mm). Then I will comment if it works.

[Virdi_248]

I want to show a photo I'm not home for two days. If I have in my phone a capture of the tracks created, I have mounted the circuit.

[chemelec]

What is the Size of your Ferrite Rod?
And have you checked the Inductance of your Coils?

My Primary Coil is 2 Layers of 30 AWG wire with 110 Turns on each Layer. CAREFULLY WOUND PERFECT LAYERS. (1.1Mh)
My Feedback Layer is 100 Turns, Wound over top of the Primary. (460uH)

[Virdi_248]

Ferrite 100x10mm (used 7cm from the surface)
coil 1 (96)
coil 1a (112)
coil 2 (69)

I also made a coil in three parts the same as in the schematic and did not work.

The unknown inductance.

I want to build this gadget, I am waiting for the microcontroller to be sent and so I can measure inductances. Http://lu6dcs.blogspot.com.es/2015/1...o-digital.html What works well is its pulse detector, many years using it and many things found.

I hope to get this pinpointer to complete the equipment. Pi chemelec, tgsl and missing a pinpointer.

[chemelec]

TYPO ERROR, 1.1Mh is actually 1.9Mh.

What is the Size of your Ferrite Rod?
And have you checked the Inductance of your Coils?

My Primary Coil is 2 Layers of 30 AWG wire with 110 Turns on each Layer. CAREFULLY WOUND PERFECT LAYERS. (1.1Mh)
My Feedback Layer is 100 Turns, Wound over top of the Primary. (460uH)

[ionut_mtb]

I just used Polyester Caps.
And a Slightly Modified Circuit, Works Good.
(My Ferrite Rod is just a 1.5 inch Long and 1/4 inch Diameter.)

[ATTACH]39660[/ATTACH]

Does it have problem with temperature changes or when turn to the sky to 45" angle? need frequent adjustment? Mine had some issues. it has very good detection distance and sensibility to small targets but is not stable. I want to built one stable pinpointer, just on/off switch, with medium detection just for coins. but i'm stil searching.

[chemelec]

Does it have problem with temperature changes or when turn to the sky to 45" angle? need frequent adjustment? Mine had some issues. it has very good detection distance and sensibility to small targets but is not stable. I want to built one stable pinpointer, just on/off switch, with medium detection just for coins. but i'm stil searching.

As with most Pin Pointers it does need Minor adjusting for Greatest Sensitivity.

[Polymer]

I just used Polyester Caps.
And a Slightly Modified Circuit, Works Good.
(My Ferrite Rod is just a 1.5 inch Long and 1/4 inch Diameter.)

[ATTACH]39660[/ATTACH]

Nice re-design Chemelec! I assume your bias design is more robust (temperature wise) than the NUPI one.
If so, please post a schematic.
I can't test circuits quickly on a breadboard, because I live in a humid & salty environment causing lots of contact problems, so I have to solder everything.

[Polymer]

I want to show a photo I'm not home for two days. If I have in my phone a capture of the tracks created, I have mounted the circuit.

Just saw your coil. Like Chemelec & others say: take your time winding the coil really well. I use double-sided sticky tape layers to make this easier.

[chemelec]

Nice re-design Chemelec! I assume your bias design is more robust (temperature wise) than the NUPI one.
If so, please post a schematic.
I can't test circuits quickly on a breadboard, because I live in a humid & salty environment causing lots of contact problems, so I have to solder everything.

Not Sure it is more Robust, But it works for me.
Mainly it gives a fairly fine Tuning Without the need for a Multi-turn Pot.

My Ferrite Rod is Embedded in a 1/2 inch Diameter ABS Rod, than Lathed with a Groove where the Coil is to be wound.
And I Wind all my coils on my Metal Lathe, at Quite High Speeds.

My Modified Schematic:
Depending on the Coil Winding, the 68K Resistor Might Need to be a Higher Value.

[Polymer]

Not Sure it is more Robust, But it works for me.
Mainly it gives a fairly fine Tuning Without the need for a Multi-turn Pot.

My Ferrite Rod is Embedded in a 1/2 inch Diameter ABS Rod, than Lathed with a Groove where the Coil is to be wound.
And I Wind all my coils on my Metal Lathe, at Quite High Speeds.

My Modified Schematic:
Depending on the Coil Winding, the 68K Resistor Might Need to be a Higher Value.
[ATTACH]39670[/ATTACH]

Thank You so much Chemelec. I will be trying this soon.
Your circuit may open the possibilitiy of using NTC/PTC for partial 'automatic' temperature compensation.

It's great you have a lathe. I hand-wind these things. Talk about ZEN meditation.

[blobber]

Nupi's pinpointer in homemade water proof enclosure.

https://youtu.be/nB_lOlpI7Vk

[Virdi_248]

I have managed to make it work. Replaced adjustable resistance of 1k for 100k and also I have changed cd4024 for the new one and now it works. The worse thing is the big size, in the future I am going to make other one small.





https://www.youtube.com/watch?v=OO_Dyu_5lew
Thank you