My take on the HH2

[waltr]

i made the pcb, out of curiosity i want to test it but at the input of the u7 I only read 6.7 volts.
Do you use MCP 604?

What is the output Voltage of U7, the LM78L05 regulator? I'll guess it is about 4V.
I will try to remember to measure the input Voltage to U7 tonight to verify what I remember.

Also do check the output of the 7660 and the input to the 78L05 with a scope.

I have an option for an MCP604 quad op-amp that actually is not used on the board that I use as an active detector.
Never did connect it to monitor battery Voltage, etc.

I am using the basic circuits for another design where I do use the MCP604 as a level-sifter/Voltage limiter to feed a PIC32' ADC input.
So the MCP604 and other parts around it can be eliminated (not installed).
Note: There is a design flaw with the Transistor to 604. The transistor should be an PNP that is referenced to 'ground' (Battery +) to act as a variable current source.
It kind of works as on the schematic but output varies with batter Voltage.

So you made the PCB from my drawing. Are you also using the PIC code I posted?

Very interested in how it works for someone else.

[waltr]

Saba,
Actual measurement at input to U7 (78L05) is 8.5V and 8.9V on two boards that I have running.
My memory was a bit off but with a drop out of 3V this has enough extra Voltage to have a ~5V regulated output (on my boards this measures 4.9V).

What are you clocking the 7660 with? The PIC's pulse output?
Which version of the 7660 are you using? What Voltage into the 7660.
Best is the 7660A and 12V input which is what I am using.

[saba]

Yes clock is from pic pulse out.
i use zener 4,7V.
Not shure for 7660 model.
I will check,maybe i made some mistake somewhere

[waltr]

Yes clock is from pic pulse out.
i use zener 4,7V.
Not shure for 7660 model.
I will check,maybe i made some mistake somewhere

Ok.The Zener was there to drop the battery Voltage to within the maximum Voltage a 7660 allows with is 10V for the 'standard'. The 7660A allows a max of 12 Volts so a dropping Zener is not required for a 12V battery.

If you have a 12V battery the zener drops 4.7V so only 7.3V goes to the 7660 and since it not 100% efficient the 7660's output is lower.
Do you have a lower Voltage Zener like 3.3V? That should increase Voltage to U7 by 1.4V to about 8.1V.

Or you can try a series resistor then a 10V zener across the 7660 to limit the Voltage. Basic shunt regulator.

[h9361]

Hello
Dear Walter
Before everything, thank you for sharing your result.
Please see the schematic, i used your schematic to edit HH1 Rev. D, added your GB, Audio part and Gain pot.
Is it possible to see it and tell me your opinion?
Thank you

[waltr]

You posted this is in multiple threads and I answered.

The other thread is not correct place due to this is not within the thread's title and subject.
Here is a good place.

What you drew is NOT what I did to add GEB.
In your schematic one of the FET switches is the target Sample the other one is the EFE sample.
I did not look at any of the timing so unknown what this will do.

My GEB uses Three Samples on the Two FET switches.
Target sample, then GEB sample on other switch then just before the next TX pulse an EFE sample using the first switch.
All timing is controlled by the PIC processor (you can use an Ardunio or other processor) or a third timing circut to do this.

[h9361]

Thanks Dear walter
Please see the new schematic, three sample, TC,EFE,GB
What do you think?

[waltr]

Thanks Dear walter
Please see the new schematic, three sample, TC,EFE,GB
What do you think?
[ATTACH]55040[/ATTACH]

On a quick look of the schematic that one should work.
Only way to really know is build and test.

Go back over my method and you'll see I did not need the extra switches, integrators, diff amp and timing circuits.
Plus very easy to adjust timing parameters when using a processor.

Also in this thread are links to GEB discussions. Follow them and read. These are where I learned what needs to be done.

[h9361]

Thanks dear Walter.
Can you tell me size, uH and damping resistor if your Coil?

[waltr]

Thanks dear Walter.
Can you tell me size, uH and damping resistor if your Coil?

The Coils I have build and used are in this thread above. Inductance is around 400uH if I remember correctly, READ this thread for that detail.
Damping resistors are around 300 to 700 Ohm (do not remember exact values). They were selected by testing with O'scope on Pre-amp output.

[green]

The Coils I have build and used are in this thread above. Inductance is around 400uH if I remember correctly, READ this thread for that detail.
Damping resistors are around 300 to 700 Ohm (do not remember exact values). They were selected by testing with O'scope on Pre-amp output.

When selecting Rd while looking at Pre-amp output, have you clipped scope lead to coil hot lead insulation to see if coil is critical damped?

[h9361]

Dear Walter
Do you have any info. about audio part of GPX 5000? Do you think we can build such audio (soft sound) with CD4046?

[waltr]

When selecting Rd while looking at Pre-amp output, have you clipped scope lead to coil hot lead insulation to see if coil is critical damped?

Never tried doing that.
I do have a resistor divider on the HH2, about 80:1, that I use to 'see' the coil wave forms.
It has been a while since I did any scope work on the HH2 so memory not great.

[waltr]

Dear Walter
Do you have any info. about audio part of GPX 5000? Do you think we can build such audio (soft sound) with CD4046?

Never anything on the GPX. I did on that schematic you referenced in another thread today.
I did model it in LTSpice and prototyped the 4046 circuit. It works.

However, for my HH2 it was so much easier to use an 8-pin PIC and write some code. This has many less parts, 1 chip, 2 caps, a few resistors and a pot.

[h9361]

Never anything on the GPX. I did on that schematic you referenced in another thread today.
I did model it in LTSpice and prototyped the 4046 circuit. It works.

However, for my HH2 it was so much easier to use an 8-pin PIC and write some code. This has many less parts, 1 chip, 2 caps, a few resistors and a pot.

You right, using 8-pin PIC is very very easy, i will try it.
Yes, Mr. FatBob has used CD4046. As you see, there are two TL072 for generating two fixed tone (i think). Now suppose that i remove the two amp and out of HH is directly connected to Pin 9 of CD4046.
Do you think we will have different tones for different metals, size or etc?! I think GPX audio isn't using two fixed tone, i think it's a range frequency.