Can pinpointer detecting thin chain?

[Nupi]

Sorry, emitter TR1

[Fabian]

What is the "immetter"?

At the same point (BC560 emitter), with the R4 connected, got the same volts: 5.1

Fabián

[Nupi]

Connect R4 again and measure the voltage at the immetter. What voltage do you measure now?
nupi

[Fabian]

Hi Fabian,
I assume that you are measuring with the L2 disconnected.

1--Take the power off
2--Disconnect the entire coil.
3--Disconnect R4 on the side of the emitter.
4--Measuring the resistors R1 + R2 should be about 100K are rotated left or right. Tell me if that's right.
5--Add the voltage back on.
6--And then measure the voltage at the emitter of TR1 to the minus. What voltage do you measure now?


nupi

Hi Nupi.

- Measurement of R1 + R2 is 103K and oscillates somewhat.

- Between the emitter of BC560 and minus, measured 5.1 v

[Nupi]

Hi Fabian,
I assume that you are measuring with the L2 disconnected.

1--Take the power off
2--Disconnect the entire coil.
3--Disconnect R4 on the side of the emitter.
4--Measuring the resistors R1 + R2 should be about 100K are rotated left or right. Tell me if that's right.
5--Add the voltage back on.
6--And then measure the voltage at the emitter of TR1 to the minus. What voltage do you measure now?


nupi

[Fabian]

Hello Nupi. I have a problem: I can not get the voltages you recommend in some zones of the circuit. I set up the board to your specifications, but can not get the 4.5 volts at the junction of R5 and C4. There I have 1.65v. Also at the junction of R4, R5, C3 and IC1 I have v 2.5. With VR2 varies between 1.65v and 2.5v.
The only difference with the instructions, is that I used a polyester capacitor 1.8 nf instead of ceramic.

Any suggestions on how to continue?

Fabian

[Qiaozhi]

Nupi Olá, você tem o arquivo no lay-circuito, seria bom!

Please read the forum rules -> Basic Rules of the Forums
and make your posts in English.

[maxm3s]

Nupi Olá, você tem o arquivo no lay-circuito, seria bom!

[Nupi]

Hi Fabián,
No, it is not necessary to put a white LED.
You can put any color of LED.You have to determine the resistance experimentally for another LED.
Regards, nupi

[Fabian]

Hi Nupi. I'm working in your PP and I want to know if in necessary to put a white led (for some matter about consumption or something like that), or can I put any color of LED there.

Thanks in advance,

Fabián

[Nupi]

Nupi, What is the Purpose of C4 & R5 on your Schematic?

Looking at the Output on an Oscilloscope or listening to the output sound, Nothing changes if you Remove them

I know very well how my circuit works. I made it myself.
With my limited knowledge of the English language (I mean, I understand it pretty well),
but if I want to write it down, then it goes wrong.This applies to all languages. With this handicap, I have to live.
But this is only one small problem. So that was a little bit about myself. I should like to ask you to be understanding,
and not immediately think of what writes the troll again.


I'll try to explain it simply.There are not one but two oscillators. The "Harley" BC560 and IC-4024.
The 4024 is not an oscillator but which are also used here as a relax oscillator beside is a 7-stage binary ripple counter with a clock input.
If you remove C4 and R5 you have no longer a relaxation oscillator.(I hope I have explained well and that you understand)


To explain it well in English you would have to ask Davor.
I do not know how big the knowledge of Qiaozhi is (or someone else) but maybe he will explain it to you, too.


Davor has a thing explained in This thread:


"Basically it is an absorption detector.
Tr1 forms a Hartley oscillator and it is biassed so that it operates in linear regime that is prone to amplitude changes.
When a metal object is introduced to the coil, the amplitude of oscillation is reduced because of the eddy current losses,
but more importantly, the transistor power consumption is enlarged, and thus the emitter voltage gets shifted. This arrangement is not new, and most pinpointers work at this or similar principle. The change in the oscillator working conditions is translated into some sort of indication.
What is new and very good here is the way this working point gets detected It is the role of 4024 that forms a relaxation oscillator with narrow strip of input signal levels that brings it from non-operation to saturation, and in a process it provides a very sensitive indication. It operates on the oscillator's envelope rather than the DC level,
pulse durations are set by pulse counting method, and in a process it provides pulsed audio. Brilliant." #137


"......Your biggest achievement with this pinpointer is the 4024 detector. It outperforms all the envelope detectors by far and wide, and it provides a straightforward beeping tone.
That said, every improvement should start from the 4024 circuit............." #300

[Nupi]

Multi-Turn Pots are Expensive. But 10, 18 or 25 Turn Trimpots are CHEAP.
A Short piece of 1/8 Inch Brass Tubing (From Hobby Shops) can be soldered to the Brass Screw Adjustment on these Trimpots, And than can be fitted with a knob for 1/8" Shafts.

Make sure the Brass Adjustment and the Inside of the Brass tube are Clean.
Carefully Than Pre-Tin the Top of the Brass Screw and partly fill the inside of one end of the tube.

Be Careful to Position it Sraight near the trimpot, than using a Weller Soldering Gun,
Heat the Tube to melt he solder in it, Than place it onto the Screw and Quickly Remove the Iron.

If all goes well it will be Straight and work really good.
On MY FIRST ATTEMPT at this, I had to Re-melt the tube Two times to get it Straight, But still didn't damage the trimpot.

Thank you for your positive and constructive contribution.
The Multi-Turn Pots are indeed Expensive and often very large.Your tip is very useful.
I have sometimes used, but I glued the shaft with two component adhesive, because perhaps the problem of the
excessive heat for the trimpot. What I did was supporting the tube so that it lasts longer.I think these tubes are ready on sale.

[chemelec]

Great solution Gary, thank you for share.

Yes I thought it would be good to post it here, Especially since Pinpointer's Usually work better with one.

[chemelec]

Nupi, What is the Purpose of C4 & R5 on your Schematic?

Looking at the Output on an Oscilloscope or listening to the output sound, Nothing changes if you Remove them

[WM6]

Great solution Gary, thank you for share.