Lrl from Italy

[brs]

Amplification
sorry for my bad used a translator

[FrancoItaly]

You must decrease the amplification until the compass and the sky effect disappears.

[brs]

Amplification of capacitor or resistance

[FrancoItaly]

If you have the 3 leds version turn P1 for less sensibility, if you have 1 led version turn P2, I think that it's not necessary hardware change.

Best Regards

[brs]

thank you franco

[brs]

http://store1.up-00.com/2016-05/1462916372161.jpg

[FrancoItaly]

I don't understand, the scheme is correct, the presence of a target is signaled by an increase in voltage to the signal input (from sensor), then at out of IC3A the signal decreases (the signal is applied to inverting input). When signal at not inverting input of IC3B is more low then 6V (Determined by the R12 / R13 voltage divider) the out of IC3B goes low (zero volt) and then the LED lights up and the buzzer sounds.

Best Regards

[brs]

Thank you Franco
accept greetings

[abdou2014]

I want to make this change. is there anyone who is interested ?

[FrancoItaly]

Before making any changes you have tested the LRL on the field ? In my opinion my LRL works only in the 100Mhz range. The low pass filter is no critic as the output is a DC voltage
with some residual RF (8Mhz).

Best regards

[Mohlrl]

hi Franco. In your opinion, transistor with hfe 450 is good?

[FrancoItaly]

Yes I think it's ok, look " http://alltransistors.com/transistor...ansistor=22466 ", 450 is the minimun value for " hFE " ( transistor gain ). Anyway for more gain you can increase C13 and/or C14. Any transistor BC...C series with 150Mhz frequency or more is ok.

[abdou2014]

location of the filter corrected .what is the resonance of LC circuit ? and why we not add a resistor for get a wideband .

[FrancoItaly]

LC resonance is about 100 Mhz, I have not measured accurately, It must be taken into account the capacitor formed by the BE junction of TR2 (about 10pF). C15 is a simple coupling capacitor with a very low impedance at the frequency of 8MHz, should at most is a simple high pass filter. The set of C15, D1, D2 and C16 constitute a full-wave rectifier, while TR5 operates in emitter follower with high input impedance and low output impedance. R15, R16, C17 and C18 constitute a lowpass filter to eliminate the residual signal at 8 MHz.
I repeat that the sensor stage is very critic for the high gain, in my opinion it should be built on a separate PCB, preferably double-sided, with components soldered directly on the copper of a part, while the other part is connected to ground and serves as a screen to prevent auto-oscillations. I will post again my original PCB.

[abdou2014]

So your device is Capacitive detector , and if we add an antenna in base of TR2 we have a Static and Capacitive Detector . I'm right ?

[goldfinder]

Sounds like he is using the capacitor as a scalar sensor to detect the gravity eminations of the minerals ( gold).
Goldfinder

[FrancoItaly]

I do not know if it is a Capacitive detector. Static presupposes very high impedance receiver, but it's not the case.

[abdou2014]

PLEASE Mr FRANCO WERE WE PUT THE VARIABLE CAPACITOR FOR TUNING. IN C9 OR C10 (8 MHz Stage). AND WHAT IS ITS VALUE?

[FrancoItaly]

In place of C 10 and the value is 22pF. Usually the variable capacitor has the range from 4 to 22pF. To test lower frequencies you must add in parallel a 10pF capacitor.

[abdou2014]

THANK YOU

[LRLMAN]

Hello dear friends I have a small obstacle to put to work my LRL I only need to complete the stage of Power-Display, I develop a PCB but this I did not work because the potentiometer 20k I put the device began to heat up and smelled burned and decided to review all the PCB but nothing; Now draw another PCB through the program called: Live Wire and PCBWizar and the program suits me the tracks as follows but I have the impression that even is not complete the PCB and I think that some lines should go to negative part and I would like to know if someone in the forum here can help me to complete the Power-Display Stage and can test it on field.

Regards.

LRLMAN.

[FrancoItaly]

Try to feed the part relating to IC2 (the stage display) with a stabilized power supply, obviously with 12V, excluding all the part related to 78l12 and IC1. With led off the absorption will be a few mA, if it is not so you have to check that there is no short circuit between the + 12V and ground. Leaving the power section disconnected connects the stabilized power supply instead of batteries and if the absorption is very high you have to control C1 and C3, sometimes it happens that the electrolytic capacitors are defective, otherwise it can also be a short circuit here between + 12V and ground.

[LRLMAN]

Originally Posted by FrancoItaly

Try to feed the part relating to IC2 (the stage display) with a stabilized power supply, obviously with 12V, excluding all the part related to 78l12 and IC1. With led off the absorption will be a few mA, if it is not so you have to check that there is no short circuit between the + 12V and ground. Leaving the power section disconnected connects the stabilized power supply instead of batteries and if the absorption is very high you have to control C1 and C3, sometimes it happens that the electrolytic capacitors are defective, otherwise it can also be a short circuit here between + 12V and ground.

Ok thanks Dear Franco, but then... how do I know which are the tracks that are missing for the pbc is properly ?? and can work well? could you help me a little ?? please.

Thank you so much for your help Franco.

receive a big hug.

Lrlman.

[abdou2014]

Is it necessary MR Franco to make two power supply. One for sensor and one for display stage. And separate them. Because I have supplied both with a single supply ?

[abdou2014]

Here is my PCB 8 Mhz