Lrl from Italy

[FrancoItaly]

I don't think, but I have send a msg with another Email. confirm if you receive.

[liudengyuand]

Ok

[liudengyuand]

I now face a problem, c18 voltage at 6.58 v, I reduce the capacity of c1 to 220 p, the decrease of the output voltage without any, c2.3.4 these three capacitance is I use 9 3 p series, I disconnect c4 and tr2 the base, the decrease of the output voltage or no, excuse me how should I solve this problem?

[FrancoItaly]

Hi liudengyuand,

if with quartz disconnected you have a DC output (more than 6V at C1 means the the stage is auto oscillating, so you have to reduce the gain by reducing C13 and / or C14. if with quartz disconnected you don't have a DC output disconnect C4 and connect quartz and if there is more than 6V DC output (this is your current case, I think) means that there is a parasite coupling and/or too much gain then reduce C13 and / or C14. It's better a double side PCB with the lower side connected to ground.

Best Regards

[liudengyuand]

Thank you for your guidance, I will slowly to solve the problem

[zakari]

Hi dear francoitaly

I made two sensor of your sensor stage similar together and components are equal
I named these A and B
when i touch antenna of A out voltage drops 20miliv and I touch antenna of B voltage drops 150 mili v

what's your opinion about this difference

thank you very much for your guidance

best regards

[liudengyuand]

I disconnect crystal, the output circuit of 0 v, I might be graffed in crystal, circuit output is 6.58 v, I remove the c13, circuit output is 5.1 v, if it's not c13, it to the actual impact on the way to detect metal? Where is my question? Is a question of tr3?

[d4rkh00d]

Hey FrancoItaly

Can I ask an schematic diagram from your 10 LED using LM3914? I'm not really good in electronics but I can Follow instructions from the schematics. Thank you.

[FrancoItaly]

Hi zakari,

The behavior of the two lrls is normal and is part of the component tolerance.

Best regards

[FrancoItaly]

Hi liudengyuand,

the amplification of sensor stage It depends mainly on the "beta" of the transistors (TR2-TR3-TR4) and therefore there will always be differences between two LRL with the same components. Balancing C13 and C14 we can get the right gain. 5.1V is Ok if touching the antenna the output drops down.

Best Regards

[FrancoItaly]

Hi d4rkh00d,

I'm not in Italy and I don't have the LM3914 display schematic, here I post a generic schematic, with reference to display (3leds) stage you must connect IC1A output to pin5 LM3914, for better adjustment can add between P1 and ground a resistance of 68K (or more).


Best Regards

[liudengyuand]

When I touch antenna, why the output voltage is higher, not lower, it is 5.17 v, when I touch antenna, it changes to 5.18 v, is this normal?

[FrancoItaly]

Usually the voltage drops down 10mV or more, perhaps you have little gain. Your PCB is double face?

[liudengyuand]

I was welded with a universal plate, not a double sided, but why is it rising instead of falling? Will you touch the antenna board, the voltage from the number of changes to the number v?

[zakari]

Hi franco

I assembled sensor stage and dis play stage .now my out put voltage is 5.34v and i touch the antenna led turn off

is this voltage is normal or is high?

is it necessary to reduce the out put voltage?

I can't test at test field because i am far from test field