Tweet
About 3 meters from test field , About my friend R3, R4 and C1 as the schematic, Two battery 9V that is to say 18v Connect with LM7812, he told the gain decreases alone and slowly, exp : If it sets the gain potentiometer to a point where the led flashes, after a few seconds the led turns off , and the sensitivity decrease ???
-
-
As I said you have to check the output of the stage sensor, the DC voltage must be very stable. Another cause can be the influence of the human body, moving the hand away after making the adjustments can cause a decrease in the signal.
Best RegardsComment
-
you was right, the DC output of the sensor stage isn't stable, What is the source of this disturbance ? What must he change ?Comment
-
Probably the stage sensor is oscillating, there is too much amplification or the defect is in the PCB. You must repeat the tuning process.Comment
-
hi franco
how are you
I don't have any self oscillation at the sensor stage
but i have self oscillation at the display stage
how can i reduce self oscillation in the display stage
R3,R4,C1 are schematic value
thank you very much
best regardComment
-
hi
I have made some many pcb
I don't have any problem for revealed the metal this lrl work absolutely
MY problem is stability of this device
some of the pcb increase and some of them decrease voltage of the ledes
all of this pcb not have self ocsilation at the sensor stage without the xtal
when the devise is stable that revealed the baried metal very easy
thank you very much mr franco for your lrlComment
-
Disconnects the output of the sensor stage and checks if there are still oscillations.
If so, increases from 22nF to 100nF the capacitor between the output and the input- of the first operational (DC amplifier) and set the potentiometer to the minimum gain.
To minimize the possibility of auto oscillations, it is advisable to use two pcb one for sensor stage and the other for display stage, plus the sensor stage pcb is better double face, with lower face connected to ground. If there are no oscillations it's possible that there is too much gain in sensor stage, In this case decrease C13 / C14 and increase C2 / C3 / C4 for to have a DC output in the range 4-6V.
Best RegardsComment
-
You can also try to change the quartz frequency for example 6 or 4Mhz. It seems strange that the DC amplifier may oscillate as there is not much gain.
Best RegardsComment
-
hi franco
thank you so much
best rgardsComment
-
hi dear franco
one of the my friend ask two question
and he want your respond about that
1-when does the led turn off? while the antenna is above the target or operator's feet is above the target
2-what's the difference reaction of the lrl when that sense the sky or compass effect and when that sense the barried metal
thank you so much
best regardComment
-
The behavior is normal for a lrl, near and on the target's vertical, the signal disappears. Instead, with the compass effect, the signal remains practically constant moving in the north / south direction or vice versa. However, the lrl must be set to not have this effect (decreasing the gain).
I would like to know the type of buried metal and the distance of revelation, thank you.
Best RegardsComment
-
display problem senior franco
i need your help franco......
my dispaly stage it is on all time.......
any help from all of you...plz
thank you all on this forumComment
-
If you refer to the schemas I put here the output of IC1A is too high, this means that the output of the sensor stage is too low, it must be about 4 to 5V. Tell me what the value is.
Best RegardsComment
-
lrl
hi franco and thanks for replay
it is crazy but ....i have 13.5 volt aoutput
my sensor work perfect......5.86 v
0 withaout crystal......155 mv on antenna
2 side pcb
but i make 1 led sensor and give me 13 volts
i tray the 3 led dispay
and somthing more senior franco....tl072 chip itray tou make whith this
tell me your opinion and thanks againComment
-
TL072 as TL082 are not suitable because did not work well with single power supply.
Best RegardsComment
Comment