Threshold Pot doesn't work

[h9361]

Where did you buy your opamps?

Is it possible to add a meter (for exp. VU or uA meter) to HH1?!

[Carl-NC]

There is a very good chance that your Chinese TL072 is not a TL072 at all. I bought some Chinese TL071 opamps, they were not TL071. Even worse, whatever they were they were a dual opamp, not even a single. I threw them away.

When you open SW2 it is critical that IC8 has ultra-low bias current or it will quickly rail out, and that sounds like what is happening.

[Carl-NC]

Is it possible to add a meter (for exp. VU or uA meter) to HH1?!

I suppose so, the collector of Q6 could drive a meter. If you want both meter & audio then add a parallel R35a, R36a, and Q6a. Adjust the R's for whatever meter you want.

[h9361]

I suppose so, the collector of Q6 could drive a meter. If you want both meter & audio then add a parallel R35a, R36a, and Q6a. Adjust the R's for whatever meter you want.

Thanks dear Carl.
Is it possible to see the attached? Is it correct ?

[Carl-NC]

Yes, that is what I was thinking.

Edit: the other side of the meter needs to be -5V, not ground.

[h9361]

Yes, that is what I was thinking.

Edit: the other side of the meter needs to be -5V, not ground.

Hello
Dear Carl
Today i did a test with 1x1m coil and have faced with some problems, but its depth detection was very very nice!
1- I think my basic vco sound intervals is fast (pitt .. pitt...), while position of my THD Pot is at first! Do you think using R22/C16 can help?
2- I have a pitch sound when my frame get down quickly and touch ground. Other words, i have action when my frame hits ground.

[h9361]

What is interesting is that my THD Pot can not mute the sound with 1x1m, but it can increase pitch and make a high sound.

[Carl-NC]

1- I think my basic vco sound intervals is fast (pitt .. pitt...), while position of my THD Pot is at first! Do you think using R22/C16 can help?

R22/C16 will have no effect on the threshold. You need to adjust R30 and/or R32.

2- I have a pitch sound when my frame get down quickly and touch ground. Other words, i have action when my frame hits ground.

If the wires have any looseness then impact will cause them to move and create a false signal.

[h9361]

Yes, that is what I was thinking.

Edit: the other side of the meter needs to be -5V, not ground.

Hello
Dear Carl
I changed R30 value and my THD problem is solved.
But i have still problem with my VU meter.
According to your advise, i built the attached circuit but i have no any reaction over meter.
Before building, i tested my VU meter, it works correctly.
I checked all of Ground (+12), -5 connections using MM and all is correct voltage.
I checked both pins of meter with MM, both voltage is -5V!!!

[h9361]

I measured voltage collector of Q6 in my HH1, it is -2.5V, while my VU meter is micro range.
Similarly, i measured voltage collector of Q6 of my meter part, it's -5V.
I think i should use Ampere meter but i don't know which range is good (uA, mA or A).
I'm sure my circuit is without any mistake, i built twice and checked more and more.

[h9361]

I measured voltage collector of Q6 in my HH1, it is -2.5V, while my VU meter is micro range.
Similarly, i measured voltage collector of Q6 of my meter part, it's -5V.
I think i should use Ampere meter but i don't know which range is good (uA, mA or A).
I'm sure my circuit is without any mistake, i built twice and checked more and more.

Sorry dear Carl.
I had a mistake, it works very very nice!
Thank you for your advise.

[Carl-NC]

Glad it all worked out!

[h9361]

Glad it all worked out!

Hello
Dear Carl
As you know, my problem was that my threshold audio (pitt...pitt..) did not mute. So, according to your advise, i decreased R30 value from 150K to 50K and 100K. The problem of muting threshold audio is solved but my coil becomes unstable with up/down. Do you have any suggestion for testing?
Thanks

[Carl-NC]

Probably you will need a design that has ground balancing. Hammerhead does not have that. There are several threads about ground balance designs.

[green]

Probably you will need a design that has ground balancing. Hammerhead does not have that. There are several threads about ground balance designs.

h9361 suggested in reply #96, I used a new PCB rev. D, now i have no noise.
Now i'm working over 4delay ground balancing (suggested by Mr. Carl.). My result is very very nice and i can work in 10us-25us with high stability over mineralization.

Don't know what the problem is. Seems to work one day, not the next.