My take on the HH2

[Carl-NC]

I want to build Mickstv's Audio part. He used JFET PMBF4393 but i can't find the FET in our country. Do you think i can use BF256 as its replacement? Can you introduce me some through hole equivalent?

You can determine this by looking at the data sheets. Most transistors (bipolar or FET) used in metal detectors are fairly generic and substitutions are easy.

I have some questions for you...

Do you know how to read data sheets?

Do you have any electronics knowledge?

Have you ever built any circuits?

Do you have an oscilloscope?

[h9361]

You can determine this by looking at the data sheets. Most transistors (bipolar or FET) used in metal detectors are fairly generic and substitutions are easy.

I have some questions for you...

Do you know how to read data sheets?

Do you have any electronics knowledge?

Have you ever built any circuits?

Do you have an oscilloscope?

Dear Carl, Sorry for my primary questions, i find 2n3819.
I asked from Mr. Mdtoday and Mr. Walter about best connection point of HH1 to Mickstv design C8.
They helped me and told their opinion but there is a different view about TP9 and TP5 (after SW2, before IC8b). Is it possible to tell me your opinion about best point?
Thanks.

[waltr]

Thanks dear walter.
I want to build Mickstv's Audio part. He used JFET PMBF4393 but i can't find the FET in our country. Do you think i can use BF256 as its replacement? Can you introduce me some through hole equivalent?

Should work fine.

[h9361]

Should work fine.

Dear Walter
Please forgive me for my questions. I want to add LM386 to Mickstv's Audio. Is it possible to see attached, do you think C and E of Q1 is true?!

[waltr]

Q1 connections do not look corret.
That is a PNP bipolar so Base pulls current down through emitter (+E to -B) to product emitter to collector current.
Also, you have it open collector so no DC collector current.
In Mickstv's circuit R12 should be to a Voltage more positive than the Q1's base.

Go back and wire per Mickstv's schematic. Place a 50-100 Ohm ressitor from Volume1 pot to Q1 emitter. Then connect the 100uF cap to emitter of Q1.

Like I and others keep telling you, prototype the circuit to see and learn.

Dear Walter
Please forgive me for my questions. I want to add LM386 to Mickstv's Audio. Is it possible to see attached, do you think C and E of Q1 is true?!
[ATTACH]55071[/ATTACH]

[h9361]

Q1 connections do not look corret.
That is a PNP bipolar so Base pulls current down through emitter (+E to -B) to product emitter to collector current.
Also, you have it open collector so no DC collector current.
In Mickstv's circuit R12 should be to a Voltage more positive than the Q1's base.

Go back and wire per Mickstv's schematic. Place a 50-100 Ohm ressitor from Volume1 pot to Q1 emitter. Then connect the 100uF cap to emitter of Q1.

Like I and others keep telling you, prototype the circuit to see and learn.

Very Thanks for your tip. I again drawn based on your explanation, i hope i understood correctly. Is it true?

[waltr]

Very Thanks for your tip. I again drawn based on your explanation, i hope i understood correctly. Is it true?
[ATTACH]55073[/ATTACH]

No. Like this.

[h9361]

No. Like this.[ATTACH]55074[/ATTACH]

Is + and - of the 100uF true?
Should R12 be connected to +VB or + 5V?
Thank you

[waltr]

Is + and - of the 100uF true?
Should R12 be connected to +VB or + 5V?
Thank you

[ATTACH]55075[/ATTACH]

I would use VB+ and connect cap as you have in schematic.
Ideally, one would use a non-polarized electrolytic cap.

[h9361]

I would use VB+ and connect cap as you have in schematic.
Ideally, one would use a non-polarized electrolytic cap.

Very Thanks dear Walter.
I had a experience with TDI with GPX coil and DF coil. My result shows that DF coil is able to detect more depth with high sensitivity.
I attached a schematic of DF coil and a pic from TDI DF coil (it belongs to Mr. Geo). Have you ever tested DF coil with your schematic?
I the schematic, R1 is damping resistor R2 is for internal coil for avoiding oscillation (White DF coil uses 4.7K). Actually, DF coil is mono just the two coils are serialized together.

[h9361]

Hello
Dear Walter
I saw Audio frequency of your schematic (555) about 2KHz, is that right?

[surfdetector]

Very Thanks dear Walter.
I had a experience with TDI with GPX coil and DF coil. My result shows that DF coil is able to detect more depth with high sensitivity.
I attached a schematic of DF coil and a pic from TDI DF coil (it belongs to Mr. Geo). Have you ever tested DF coil with your schematic?
I the schematic, R1 is damping resistor R2 is for internal coil for avoiding oscillation (White DF coil uses 4.7K). Actually, DF coil is mono just the two coils are serialized together.
[ATTACH]55081[/ATTACH]
[ATTACH]55082[/ATTACH]

I made a dual field coil for use on my Crossbow Classic which is a variation of the Hammerhead. I did a video on my Youtube channel of the construction.
https://youtu.be/vyY3-dSVbQs

[waltr]

Hello
Dear Walter
I saw Audio frequency of your schematic (555) about 2KHz, is that right?

For the 555 probably correct.
However, read further and you'll find I replaced the 555 with a PIC12F1501 that creates the audio tones.

[h9361]

For the 555 probably correct.
However, read further and you'll find I replaced the 555 with a PIC12F1501 that creates the audio tones.

DO you remember your PIC audio frequency?

[h9361]

I made a dual field coil for use on my Crossbow Classic which is a variation of the Hammerhead. I did a video on my Youtube channel of the construction.
https://youtu.be/vyY3-dSVbQs

Very nice coil.
Thank you.