Threshold Pot doesn't work

[Carl-NC]

You can run the pulse rate higher but you need to pay attention to heat dissipation. Usually a higher pulse rate requires a shorter TX pulse. You also need to pay attention to timing constraints, especially with the EFE pulse spacing.

What are you trying to accomplish?

[h9361]

As you know, i built HHD with GB.
But HHD has a low sensitivity to nugget and thin foil.
First, i want to increase frequency for fast responding.
Second, set delay time to 8us.
Third, change 5534 by GPX amp.
Maybe i can increase its sensitivity to thin foil.

[Carl-NC]

OK, then yes, running a higher pulse rate will help, and you do not need 100us for the TX pulse. 50us is plenty, even less if you like. Lower delay will also help.

[h9361]

OK, then yes, running a higher pulse rate will help, and you do not need 100us for the TX pulse. 50us is plenty, even less if you like. Lower delay will also help.

Dear Carl
I set sample delaying to 8us and sample width to 22us. Its sensitivity went very high and now can detect foil of cigarette.
But about Frequency, it only works up to 1.3-1.4 KHz (PW=50us). I'm trying to change my timing.
During changing, i realized that i have to increase my TX pulse if i want to increase frequency because my sensitivity will be low. If i increases TX-PW, my sensitivity be high.
Now, i tested high frequency (up to 5KHz) with 118us TX-PW, but it didn't work.

Anyway, i want to make a DD Coil for my HHD.
I 'm going to connect TP4 to O-Scope, then moves RX to TX coil.
Is it possible to guide me how to understand location of RX is correct via monitoring O-scope?
Thanks.

[Carl-NC]

If you set the frequency to 5kHz that is a period of 200us. Subtract 118us and you have 82us for the RX. Subtract 8+22us for the first sample and you have 52us for the GB pulse and EFE pulses. That's not enough time. You need to draw out a timing diagram and figure out all the timing pulses first. For small targets (foil) you should not need 118us.

When you get the DD coil connected post the TP4 waveform and let's see what it looks like.

[waltr]

In the thread "my take on the HH2" I have scope pictures of trying to balance a DD coil.
Take a look.

[h9361]

In the thread "my take on the HH2" I have scope pictures of trying to balance a DD coil.
Take a look.

Sorry for late reply.
Thanks dear Walter.

[h9361]

If you set the frequency to 5kHz that is a period of 200us. Subtract 118us and you have 82us for the RX. Subtract 8+22us for the first sample and you have 52us for the GB pulse and EFE pulses. That's not enough time. You need to draw out a timing diagram and figure out all the timing pulses first. For small targets (foil) you should not need 118us.

When you get the DD coil connected post the TP4 waveform and let's see what it looks like.

Thank you dear Carl.
According to your guiding, i changed my timing and could adjust it.
Now, my HHD is working 4.5KHZ but damping resistor gets very hot. So, i had to decrease it 2-3KHz.
I have a request about output audio from speaker. Now, i'm using a speaker 150R but i think maximum audio volume of HHD is still low.
Do you have any suggestion or guidance for more increasing audio volume?
Thanks.

[Carl-NC]

Damping resistor power dissipation will double if you double the pulse rate.

Design a better audio driver. For example, you could use an LM386.

[h9361]

Damping resistor power dissipation will double if you double the pulse rate.

Design a better audio driver. For example, you could use an LM386.

Thanks.
Is it possible to see the attached, do you think it's correct?

[Carl-NC]

Without reading the data sheet I don't know for sure, but it looks about right.

[h9361]

Without reading the data sheet I don't know for sure, but it looks about right.

Hello
Dear Carl
I built the LM386 with Gain 200 and connected its input to Pin3 of IC9.
My audio is working but its level is very very low, even lower that its original level.
I think it needs an amplifier between pin3 of IC9 and input of LM386.
Do you have any suggestion?
Thanks.

[Carl-NC]

Maybe try a different speaker.

[h9361]

Maybe try a different speaker.

I tested it with following speaker:
150R
8R-0.3W
8R-0.5
8R-1W
16R-0.5W
All of them is very very low level.

[h9361]

I tested it with following speaker:
150R
8R-0.3W
8R-0.5
8R-1W
16R-0.5W
All of them is very very low level.

sorry, i used 5V for 386.
I changed it to 9V, it's OK.
Thanks