Whites Surf PI schematic

[Qiaozhi]

Hello.
I have a question about the surf 1.2 delay test piont.
If I observe the pulse at tp and measure the time with scope... Is the lenght of the pulse the actual delay time?
How to measure the actual sampling time if I want to set it
at some desired value? Can someone explain or direct me to the right post?

The signal at the test point (TP1) is a delayed version of the TX signal. i.e. the main sample delay.
The main sample pulse can be found at U4 pin3, and the EF pulse is at U4 pin4.

[homefire]

Delay is from the End of Tx Pulse to the Start of Sample times.

[peppe30679]

Hello guys
I have a little problem with my SurfPi (Silverdog Kit): the detector in the air work well, but if i bring the coil to the ground, receive sound even if it does not detect metals (false signal).
Do i need to adjust the trimmers better?
Thanks for your help

[waltr]

Check this forum for discussions about Mineralized Ground.
Could be there is Metal in the ground where you tested.
Possibly just increase the Sample Delay time.

[ionut_mtb]

Hello guys
I have a little problem with my SurfPi (Silverdog Kit): the detector in the air work well, but if i bring the coil to the ground, receive sound even if it does not detect metals (false signal).
Do i need to adjust the trimmers better?
Thanks for your help

If detector beep's every time you sweep it might be earth field elimination problem. If have oscilloscope check sample1 and sample2 to have same width. if not check values of the to be exactly the same as in schematic.

[peppe30679]

Thanks for the reply.
Yes, i live in mineralised zone (volcanic area), but also vlf detector work well: i'm sure it's a calibration problem...... i'll try, but unfortunately i haven't an oscilloscope.

[scs]

In circuit there is a problem with creating the sound. Everybody make" Surf" and no one notices ...

[ionut_mtb]

In circuit there is a problem with creating the sound. Everybody make" Surf" and no one notices ...

as long as is working... no one thought about it. is the 4066 D switch cutting over audio signal?

[scs]

The output transistor is closed for a long time and loose for a short time. It should be flip.

[scs]

Control output sound transistor???

[tifred]

Good airplan SCS

[ionut_mtb]

The output transistor is closed for a long time and loose for a short time. It should be flip.

Control output sound transistor???[ATTACH]41325[/ATTACH]

Little hard to understand for me the audio. In the way i can explain, sample from ic4D 4093 closes the switch ic7d 4066, result audio transistor Q6 off. Aprox 100us off Q6, rest of signal (1450us-100us=1350us) on. Why? What we hear in the audio, not sample1 voltage change? What is cutting ic7d switch?

[waltr]

Little hard to understand for me the audio. In the way i can explain, sample from ic4D 4093 closes the switch ic7d 4066, result audio transistor Q6 off. Aprox 100us off Q6, rest of signal (1450us-100us=1350us) on. Why? What we hear in the audio, not sample1 voltage change? What is cutting ic7d switch?

[ATTACH]41326[/ATTACH]
[ATTACH]41327[/ATTACH]

U7D switching is what creates the Audio Tone (frequency of audio is Same as Coil pulse frequency).
Then the LEVEL of the signal through D3 Modulates the Amplitude (loudness) of the Audio tone.

So when all is properly adjusted and metal come under the coil the Audio tone increases in volume.

[ionut_mtb]

U7D switching is what creates the Audio Tone (frequency of audio is Same as Coil pulse frequency).
Then the LEVEL of the signal through D3 Modulates the Amplitude (loudness) of the Audio tone.

So when all is properly adjusted and metal come under the coil the Audio tone increases in volume.

I see U7D switch only put the base of transistor to ground, on and off. the signal from cd4093 is not going to transistor base.

edit: the audio signal that come through D3, from sample1 is cutted by U7D switch, result frequency of audio and voltage variation of sample1 give the amplitude. right?

[waltr]

I see U7D switch only put the base of transistor to ground, on and off. the signal from cd4093 is not going to transistor base.

You need to LOOK at the Whole schematic.
U7D is switched at the SAME Rate as the 4093 (switched Once per Pulse/sample cycle).
The LEVEL of the signal through D3 ALSO goes to the base of Q6.