Threshold Pot doesn't work

[h9361]

No changes needed.

Thank you.
Dear Carl, i have a technical question about 78L05 in HHD schematic. I need to learn about it.
As you know, pine 3 is output and pine 1 is input, but you used the pines as reverse in HHD.
Is it possible to tell me why? I am learning about it.
Thank you.

[Carl-NC]

All of the 78Lxx regulators I have seen have this pinout:


You built the HHD circuit, did you have to install the 78L05 backwards?

[h9361]

All of the 78Lxx regulators I have seen have this pinout:


You built the HHD circuit, did you have to install the 78L05 backwards?

See attached, the pinout of LM7805 is different.

[Carl-NC]

The 7805 and 78L05 are entirely different parts.You can use the 7805 in place of the 78L05 but you need to correct the pinout.

[h9361]

The 7805 and 78L05 are entirely different parts.You can use the 7805 in place of the 78L05 but you need to correct the pinout.

Dear Carl
I need more than 100uA for +-5V in my PCB.
Do you think it is OK if i only replace the both 78L05 and 79L05 with LM7805 and LM7905?

[Carl-NC]

Yes, just make sure you get the pins correct.

[h9361]

No changes needed.

Thank you.
I sent you a private message, please check it.
Thanks again.

[h9361]

Yes, just make sure you get the pins correct.

Dear Carl
I am learning about electronic and shematics.
Please see the attached, it is the clamping-Diode part.
My question is, what will happen if we use model 2 instead of model1?

[h9361]

Yes, just make sure you get the pins correct.

Hello Dear Carl
As you know, i am trying to find a good solution for Iron detection in my HHD.
Now, i am finished micro version of my HHD with GB, it is very nice.
But i want to add it an Iron rejection.
According my research,
Iron detection in the GPX series is usually based on three time intervals where the return signal is analyzed in each interval.
The basic idea: The device measures the return signal at three different time intervals after sending the TX pulse.
Different metals have different responses in these intervals.
Iron usually responds strongly in the first or second intervals (the earlier intervals).
For better under standing, see the pictures:


As you know, we should see at the TX turn-on response curve where iron is much different than non-ferrous.
A probable rule for decision IRON/non-Iron can be as follows:

Before adding and testing on my micro, please see the method and tell me your suggestion or any correction.
For exp, tell me your suggestion about
1- number of Delay (in above, i used three delays)
2- Delay values (S1, S2 and S3).
3- Sample width for S1, S2 and S3
4- Your edit for rules R1 and R2
5- Your suggestion for adding Iron threshold (for exp, 0.6 and 0.4 ). Do you think i can use a one threshold instead of both 0.6 and 0.4?
Thank you.

[Carl-NC]

Please see the attached, it is the clamping-Diode part.
My question is, what will happen if we use model 2 instead of model1?

R15 limits the clamp current through the diodes. Moving it to the other side means you are directly applying 400V to the diodes. They will immediately burn up, and 1us later the opamp will burn up.

[Carl-NC]

Iron detection in the GPX series is usually based on three time intervals where the return signal is analyzed in each interval.

You can do it this way and it will probably work fairly well in air. I have no idea on the timing, you will have to experiment and find out. But when you add mineralized ground the results may prove to be useless.

I believe that Minelab iron ID is not done this way, rather they sample the TX-on target response where you have both a resistive and a reactive signal. This only works when using an IB coil like a DD. ITMD3 shows some responses:



Mineralization limits the effectiveness of this method as well.

[h9361]

You can do it this way and it will probably work fairly well in air. I have no idea on the timing, you will have to experiment and find out. But when you add mineralized ground the results may prove to be useless.

I believe that Minelab iron ID is not done this way, rather they sample the TX-on target response where you have both a resistive and a reactive signal. This only works when using an IB coil like a DD. ITMD3 shows some responses:



Mineralization limits the effectiveness of this method as well.

Thank you for your valuable information.
I have tested this way and i adjusted my sampling on TX when is on and i used the following schematic.

This schematic works very nice only Concentric coil. I also tested it on DD coil but its sensitivity is only for big object, not small targets.
According to my tests, CC coil makes a high decrease/increase voltage, but DD coil can not.
Do you have any suggestion for increasing sensitivity on DD on this schematic or on micro?
Thanks

[Carl-NC]

Sorry, I don't know.

[kt315]

Thank you for your valuable information.
This schematic works very nice only Concentric coil. I also tested it on DD coil but its sensitivity is only for big object, not small targets.
According to my tests, CC coil makes a high decrease/increase voltage, but DD coil can not.
Do you have any suggestion for increasing sensitivity on DD on this schematic or on micro?
Thanks

let us to know you county, note a flag in the icon left.

[h9361]

Sorry, I don't know.

Sorry dear Carl for my asks,
Do you remember frequency responses for the two channels in HHD?
Thanks