Lrl from Italy

[FrancoItaly]

Hello everyone and Mr. Franco. Mr. Franco, I am using a 14.7456 MHz crystal. How do I know what a good harmonic setting is for the c10 capacitor? When I turn the c10 trimmer, the output voltage of the sensor reaches its maximum in one place and the lowest in another. Where is the good harmonic?

It's ok when the output voltage of the sensor stage reaches its maximum.

[hoshi]

Hi dear friend Mr jeg
Your plan will not work properly

[Jeg]

Hi dear friend Mr jeg
Your plan will not work properly

Hi hoshi
What do you mean my friend? Its a simple differential amplifier.

https://www.electronics-tutorials.ws/opamp/opamp_5.html

[JHERICKU]

hello to all and to friend franco..I tried the 8mhz circuit display with 1led..Can u advice me if I got the correct output?when I turned on the potentiometer with the trimmer maximum I got 4 or 5.+ volts on resistor which connecting to sensor stage.When I connect the multimeter probe the beep and led goes off after I removed it the buzzer and keds on again...What do u think Franco?
Ps. The buzzer and led high and low when turning the potentiometer and trimmer..

[JHERICKU]

Hey Jh
Print the circuit and the board drawing and compare them to find out the components. If you have problems then put in a red circle what you need to know, and help will arrive.
ps. Why don't you use the other circuit with the trimmers?

I used it already Jeg..When I measured the output on resistor connecting on sensor stage,I got 4/5+.volts and the bezz and leds off..When I remove the test probe the buzz and leds goes on again..Do u think I got the correct output on display?
Ps..I used the display with 1 led..

[Jeg]

Hi Jh


Your voltage levels at sensor's output look that they are normal.
Assuming that your circuit is correct, then try the following.


When your voltmeter is connected alter your potentiometer to adjust again the buzzer/led threshold. Normally you will be able again to turn on your led.


Find a way to firm your meter's probes on the right points and then move your hands away to see if there is a variation on numbers. Then attach antenna with your hand and confirm that the output voltage drops down.



In general, device interacts with your body as it uses it to close the circuit between device and earth. Your hand acts as a capacitor plate. When you adjust your device your hand has to be firm and steady attaching the handle of your device or your aluminum box.


Regards

[JHERICKU]

Hi Jh


Your voltage levels at sensor's output look that they are normal.
Assuming that your circuit is correct, then try the following.


When your voltmeter is connected alter your potentiometer to adjust again the buzzer/led threshold. Normally you will be able again to turn on your led.


Find a way to firm your meter's probes on the right points and then move your hands away to see if there is a variation on numbers. Then attach antenna with your hand and confirm that the output voltage drops down.



In general, device interacts with your body as it uses it to close the circuit between device and earth. Your hand acts as a capacitor plate. When you adjust your device your hand has to be firm and steady attaching the handle of your device or your aluminum box.


Regards

Hi Jeg.I am not yet on sensor stage..The voltage I got is from the display circuit,the R10 from ic3a pin3..I will try to finish the sensor stage today..
ps..I do not have voltmeter so I used the 1 led display..

[FrancoItaly]

Hi Jh


Your voltage levels at sensor's output look that they are normal.
Assuming that your circuit is correct, then try the following.


When your voltmeter is connected alter your potentiometer to adjust again the buzzer/led threshold. Normally you will be able again to turn on your led.


Find a way to firm your meter's probes on the right points and then move your hands away to see if there is a variation on numbers. Then attach antenna with your hand and confirm that the output voltage drops down.



In general, device interacts with your body as it uses it to close the circuit between device and earth. Your hand acts as a capacitor plate. When you adjust your device your hand has to be firm and steady attaching the handle of your device or your aluminum box.


Regards

I state that the calibration inside the laboratory is difficult due to the many disturbances and the calibration must be done with the antenna inserted. Once the right value at the sensor stage output has been established, it connects to the display stage and any measurements, if the LEDs do not light up by varying the threshold, then the controls must be done on the display stage. If you want to measure the output on the collector of TR4 with the oscilloscope, the signal at the sensor stage output goes to zero.

[JHERICKU]

Thank u franco..I will finish the sensor stage today and update u so soon..Thank u..

[Jeg]

Hi Jeg.I am not yet on sensor stage..The voltage I got is from the display circuit,the R10 from ic3a pin3..I will try to finish the sensor stage today..
ps..I do not have voltmeter so I used the 1 led display..

There is a communication barrier my friend. When you finish your sensor with the antenna in place we talk again.


Tnks Franco

[Jeg]

If you want to measure the output on the collector of TR4 with the oscilloscope, the signal at the sensor stage output goes to zero.

Why is that Franco? I don't remember noticing this. Oscilloscope has a high input impedance.

[FrancoItaly]

Why is that Franco? I don't remember noticing this. Oscilloscope has a high input impedance.

The oscilloscope has 1M impedance with few picofarads, however this is what happens, this shows how sensitive and critical the sensor stage is.

[JHERICKU]

There is a communication barrier my friend. When you finish your sensor with the antenna in place we talk again.


Tnks Franco

Hell Jeg..I have finish both the display and sensor..When I turn on there is a tiny sound coming from the buzzer..when I turn the potentiometer and trimmer there is no effect..no buzz and leds on only the tiny sound from the buzzer..

Ps.I used Bc547b,10k potentiometer trimmer..
where should I put the test probe to measure the output dc?
Thank u in advance..

I am sorry for my badproject..I am not an electronic eng noraquire formal education about electronic..I badly meeding this device so I am trying my best build..

[Jeg]

Hi friend
Looks like something is wrong, but wait for Franco to tell his opinion as he is very experienced on this.


(try connecting your voltmeter at the output of your sensor. When you touch the antenna, does the output signal drops?)

[FrancoItaly]

Hi friend
Looks like something is wrong, but wait for Franco to tell his opinion as he is very experienced on this.


(try connecting your voltmeter at the output of your sensor. When you touch the antenna, does the output signal drops?)

Yes, otherwise it could mean that there is a self oscillation. By touching the antenna a part of the signal on the base of TR2 (the mixer) is absorbed by the body and therefore the signal amplified by the sensor stage decreases slightly.