VLF MD (by Sascho - Varna)

[aft_72005]

hi aft_72005
I have a feeling I collected MD vlf on WRONG way , Can you connect the part with pcb show the sites of the right. You can use Paint software.
Thank you


Greetings

Hi Salih
Sascho VLF detector is not easy project , you need for calibration to oscilloscope.
Best regards.

[salih]

Is there one Try Detector VLF MD in the ground
What are the results

[salih]

help

Hi salih
Why without shield?? You must be shield it , then begin tune null point.
I am not found more free time, install PCB to box yet!!! , but all laboratory test
Is OK , without problem .
Best regards.

hi aft_72005
I have a feeling I collected MD vlf on WRONG way , Can you connect the part with pcb show the sites of the right. You can use Paint software.
Thank you


Greetings

[Pompey]

You can use jpg file .With any image editor you can get the correct size of the pcb.

[smity]

Thank you. But I have not installed AutoCad and I can not open (. DWG) files.

[Pompey]

http://geotech1.com/forums/showthrea...t=13817&page=2 Here is PCB ,made by LETO. Everything is tested and works.With 19cm OO coil 18mm bronze coin - 38sm in air with adjusted ground pot.

[smity]

Share please proven PCB in (lay.) file. Thank you.

[aft_72005]

hello aft_72005
I built this detector without shield , The results were not satisfactory
Have you been tested in the field and What are the results.
Regards

Hi salih
Why without shield?? You must be shield it , then begin tune null point.
I am not found more free time, install PCB to box yet!!! , but all laboratory test
Is OK , without problem .
Best regards.

[salih]

Hi all
I forgot said about my latest result with Sascho detector (the best vlf detector).
Test coin dia . 28mm, coil dia. 19cm shielded. Test conditions, on the
Workbench ,working frequency = 5.7Khz
From 30 cm at air I having clearly move on meter needle and 40cm is weaker.
Discrimination , working good.
Stability, at during five hour continues working on the workbench, excellent.
Best regards.

hello aft_72005
I built this detector without shield , The results were not satisfactory
Have you been tested in the field and What are the results.
Regards

[aft_72005]

Hi all
I forgot said about my latest result with Sascho detector (the best vlf detector).
Test coin dia . 28mm, coil dia. 19cm shielded. Test conditions, on the
Workbench ,working frequency = 5.7Khz
From 30 cm at air I having clearly move on meter needle and 40cm is weaker.
Discrimination , working good.
Stability, at during five hour continues working on the workbench, excellent.
Best regards.

[aft_72005]

………….And again Hi unregistered
I recheck discrimination, it is working well now .
Best regards.

[aft_72005]

Hi,Aft!With audio disc 200k (500k to me) after ground balancing turn on the switch for audio disc and by 200k choose the level to discriminate iron.It works good.But every time when you need to groundbalancing you must turn audio disc off-balancing to ground and again turn on.

Hi unregistered
Thanking for your guide.
Best regards.

Hi,Aft!With audio disc 200k (500k to me) after ground balancing turn on the switch for audio disc and by 200k choose the level to discriminate iron.It works good.But every time when you need to groundbalancing you must turn audio disc off-balancing to ground and again turn on.

[aft_72005]

Many thanks for your help and attention

Hi,Aft!I think that you may even without oscilloscope to null the coils -pin1 NE5532 -less reading.With oscilloscope I measure exactly wire from Rx coil .First by changing cap 100nf(or 150nf) of Rx coil -you must achieve biggest amplitude in Rx (Coils must be nulled before making that)After achieving most amplitude in RX -try to null coils again to make minimal reading in RX.Then your detector must work like it should.Try to make ground balance by trimer.If is not possible-sound appear only in one direction -then change da cap 3,3* nf.Change this cap so the potentiometer 10k must be somewhere in the middle when the ground is adjusted.Discrimination - I put varistor 100k to adjust discrimination.DIscrimination must be adjusted once time - without extended potentiometer.Adjusting disc affects the ground balance.
1. Make the coils nulled.(shielded coils)
2. Try to make Rx in full resonanse by changing cap* (max amplitude in Rx)
3. When max amplitude is achieved in Rx -try to null again by slightly moving coils for less reading in NE5532 ,or directly otput RX (with oscilloscope)
4.Now for the test you may put C comp (from 10 to 100 pf) to get amplitude in rx most minimal.If adding C comp* increases amplitude-you must move coils to make null,but from other side - then C comp decreases amplitude in Rx.
5.Try with a little ferrite to adjust ground.(to me ferrite is about 8mm diameter and 3sm long.Don`t move ferrite too close to the coils.If sound appears only when ferrite goes to the coils ,you must increase 3,3nF* cap To me -270pf.(Disc varistor must be set in the middle).When you make ground -try with little iron - meter should go left when sound appears,and for coloured metals -right.If no,or sound is no like should it be,or you can not adjust the ground -you must turn around the Rx coil and again 1,2,3,4,5 If everything correct by varistor 100k (discrimination) you should get the place where meter start to move left for irons,and right for coloured metals.Once adjusted -make the ground again and your detector is ready :P.Disc. 100k must be in the pcb,not outside the box.Once adjusted you don`t need to adjust again.outside the box must be Ground pot,SENS,VOLUME and meter ofcourse
I`m not expert this is my third pcb -that was the way which I used to get my detector to work.I hope all that will at least little help you.

Hi unregistered
Many thanks for your help and attention.
I done all of steps that you said. Minimum null , tuning receiver thank for maximum read
And ………..
At the first ,I think ,this detector be able reject iron item . I built tgsl detector by iviconic
It is be able mask iron item almost completely very good.
But I understand now, this detector (Sascho vlf) cannot mask iron , meter divide to two section ,Ferro
And non ferro .
My meter full scale is 500 microampere , but seem most time apply more voltage
To it. For stoppage from damaging it , need two silicon diode limiter on meter pin.
Best regards.

Hi,Aft!I think that you may even without oscilloscope to null the coils -pin1 NE5532 -less reading.With oscilloscope I measure exactly wire from Rx coil .First by changing cap 100nf(or 150nf) of Rx coil -you must achieve biggest amplitude in Rx (Coils must be nulled before making that)After achieving most amplitude in RX -try to null coils again to make minimal reading in RX.Then your detector must work like it should.Try to make ground balance by trimer.If is not possible-sound appear only in one direction -then change da cap 3,3* nf.Change this cap so the potentiometer 10k must be somewhere in the middle when the ground is adjusted.Discrimination - I put varistor 100k to adjust discrimination.DIscrimination must be adjusted once time - without extended potentiometer.Adjusting disc affects the ground balance.
1. Make the coils nulled.(shielded coils)
2. Try to make Rx in full resonanse by changing cap* (max amplitude in Rx)
3. When max amplitude is achieved in Rx -try to null again by slightly moving coils for less reading in NE5532 ,or directly otput RX (with oscilloscope)
4.Now for the test you may put C comp (from 10 to 100 pf) to get amplitude in rx most minimal.If adding C comp* increases amplitude-you must move coils to make null,but from other side - then C comp decreases amplitude in Rx.
5.Try with a little ferrite to adjust ground.(to me ferrite is about 8mm diameter and 3sm long.Don`t move ferrite too close to the coils.If sound appears only when ferrite goes to the coils ,you must increase 3,3nF* cap To me -270pf.(Disc varistor must be set in the middle).When you make ground -try with little iron - meter should go left when sound appears,and for coloured metals -right.If no,or sound is no like should it be,or you can not adjust the ground -you must turn around the Rx coil and again 1,2,3,4,5 If everything correct by varistor 100k (discrimination) you should get the place where meter start to move left for irons,and right for coloured metals.Once adjusted -make the ground again and your detector is ready :P.Disc. 100k must be in the pcb,not outside the box.Once adjusted you don`t need to adjust again.outside the box must be Ground pot,SENS,VOLUME and meter ofcourse
I`m not expert this is my third pcb -that was the way which I used to get my detector to work.I hope all that will at least little help you.