PI Audio

[mickstv]

Thanks Dear mickstv.
Can you tell me your opinion about best point of HH1 for connecting to Mdtoday's Audio or your audio schematic ?

Directly after the integrator stage at c19 on HH circuit.

But my output circuit won't work correctly with the HH circuit unless you modify it to do ground balance...

Micro control with three sample taken, s1 s2 (gb) s3 (ef cancel)

S1+ S3 - S2

[h9361]

Directly after the integrator stage at c19 on HH circuit.

But my output circuit won't work correctly with the HH circuit unless you modify it to do ground balance...

Micro control with three sample taken, s1 s2 (gb) s3 (ef cancel)

S1+ S3 - S2

Thanks, your mean after SAT (after SW2)?
Yes, i'm going to add GB with S1,S2 and two EFE

[mickstv]

Thanks, your mean after SAT (after SW2)?
Yes, i'm going to add GB with S1,S2 and two EFE

No pin1 of IC8a. Forget about the HH sat, the rest of the circuit has a manual threshold control, which is better for small target detection.

It's easier to do three samples the you only need one integrator.

S1 about 5us, S2 130us and S3 125us all approx. Then you adjust the delay between S1 and S2 to ground balance

[h9361]

No pin1 of IC8a. Forget about the HH sat, the rest of the circuit has a manual threshold control, which is better for small target detection.

It's easier to do three samples the you only need one integrator.

S1 about 5us, S2 130us and S3 125us all approx. Then you adjust the delay between S1 and S2 to ground balance

Thanks.
Your mean is after C19 or before it?

[mickstv]

Thanks.
Your mean is after C19 or before it?

You don't need and circuit after c19 on the HH

[Elliot]

Should be possible using a circuit similar to what the TDI-SL has. I'll see if I can figure it out. Realize though that by making the VCO more responsive near the balance point you will end up with a much more "lively" audio threshold.

I had a look at the TDI-SL circuit. I think a simpler version (less components) may be possible. I agree with your comment about the risk of a "lively" audio threshold, but we deal with those in all-digital machines these days (eg NOX). A way around it is to have an adjustable width dead band, or to wind back ones' threshold a bit. I'd like to give it a go on my breadboard if you can come up with a potential design solution.

[h9361]

I had a look at the TDI-SL circuit. I think a simpler version (less components) may be possible. I agree with your comment about the risk of a "lively" audio threshold, but we deal with those in all-digital machines these days (eg NOX). A way around it is to have an adjustable width dead band, or to wind back ones' threshold a bit. I'd like to give it a go on my breadboard if you can come up with a potential design solution.

See TDI PCB.

[h9361]

You don't need and circuit after c19 on the HH

Thanks. Do you think i can put a GAIN Pot in Mr. Mdtoday's schematic?

[mickstv]

Thanks. Do you think i can put a GAIN Pot in Mr. Mdtoday's schematic?

What do you mean by "gain pot" ?

[h9361]

What do you mean by "gain pot" ?

Actually, i want to put a pot over my unit like TDI for controlling GAIN.

[mickstv]

Actually, i want to put a pot over my unit like TDI for controlling GAIN.

Your better off having your gain control on the preamp...

This circuit has set values for a reason, the first opa1642 has to be adjusted to 0mv output with no signal input otherwise the output won't work correctly. So a gain control in these stages will cause a offset issue with the circuit....

BTW. I've been using this circuit for a few years and works fine....

[Elliot]

See TDI PCB.[ATTACH]55104[/ATTACH]

Thanks H9361, but I was only referring to breadboarding an alternative audio section, not an entire TDI.

[h9361]

Your better off having your gain control on the preamp...

This circuit has set values for a reason, the first opa1642 has to be adjusted to 0mv output with no signal input otherwise the output won't work correctly. So a gain control in these stages will cause a offset issue with the circuit....

BTW. I've been using this circuit for a few years and works fine....

Thanks dear mickstv for your guiding.
I want to add GB part to HH1 with Mr. Mdtoday's Audio schematic. I hope i have different audio frequency than different metals so that i can almost discriminate metals.
Please see attached, it belongs to one user that tested different metals in Oscilloscope.

[mickstv]

Thanks dear mickstv for your guiding.
I want to add GB part to HH1 with Mr. Mdtoday's Audio schematic. I hope i have different audio frequency than different metals so that i can almost discriminate metals.
Please see attached, it belongs to one user that tested different metals in Oscilloscope.

[ATTACH]55118[/ATTACH]

I suggest you start a new thread for help regarding this one.

Looks like something Moodz was playing with maybe ask in the corresponding thread...

BTW in reality it's next to impossible to accurately discriminate using PI, objects at different orientations have different TC....

[Qiaozhi]

Thanks dear mickstv for your guiding.
I want to add GB part to HH1 with Mr. Mdtoday's Audio schematic. I hope i have different audio frequency than different metals so that i can almost discriminate metals.
Please see attached, it belongs to one user that tested different metals in Oscilloscope.

[ATTACH]55118[/ATTACH]

As mickstv said, attempting to discriminate on a PI using target conductivity is a fruitless task.