Need help Gary metal detector

[Qiaozhi]

I mean, I had the circuit to 1000HZ. Current 230MA. Depth increased.
Perhaps the problem is the coil. I have done two circuit boards are the same. I use the NE555. You are also right?
Hope is caused by detection of small low coil current.

Your detection problem is not low coil current. As Gary says, the current is actually a little too high. Please check the following, as they can all cause lack of sensitivity:

1. Sample pulse delay time - may be too long.
2. Sample pulse width - may be too short.
3. Wrong value of damping resistor.

You will need a scope to check these.

[yhl]

I have followed Gary PI 1 circuit. Assembled two circuit boards. Has not changed R5/15K R7/3.3K R9/4.7K .
Do I need a true coil. To a 20CM0.8MM data to me.

[yhl]

I suspect the problem is the coil. Because I do not have a real coil. No inductance tester. Only be estimated. My English is not good. Can only say that China's English. Hehe

[yhl]

IC1 I am using LM317. Will be affected?

[WM6]

I suspect the problem is the coil. Because I do not have a real coil. No inductance tester. Only be estimated. My English is not good. Can only say that China's English. Hehe

Here you have all instruments you need (inductance meter too).

http://www.sillanumsoft.org/prod01.htm

A l l f o r f r e e ! Dont say anymore that you have any meter.

You need to build only a probe like this:

[Qiaozhi]

Here you have all instruments you need (inductance meter too).

http://www.sillanumsoft.org/prod01.htm

A l l f o r f r e e ! Dont say anymore that you have any meter.

You need to build only a probe like this:

WM6 - Have you tried it?
If so, how good is it?

[WM6]

WM6 - Have you tried it?
If so, how good is it?

Yes I have tried one of previous version without ZRLC modul meter.
Tried scope and spectrum analyser - it is working fine (how it works on someway depend on sound card sampling). Test was done under Win XP SP2.

I will try newest 2011 version with ZRLC meter (under Win CE on mini notebook) too.

http://www.sillanumsoft.org/ZRLC.htm

Here how to build probe (error correction interface) for ZRLC meter:

http://www.marucchi.it/ZRLC_web/INTERFACCIA_ZRLC_p.pdf

I have tried different free PC sound card scopes software and mostly are working ok in field of audio frequencies. Well enough for MD builders.

If one wish to try some different here some others free scope software on net:

http://www.electronics-lab.com/downloads/pc/index.html

[yhl]

I do not know ，I had to use the oscilloscope. Do not know how to measure your pulse.

[WM6]

I do not know ，I had to use the oscilloscope. Do not know how to measure your pulse.

If all goes according to plan there is no need to use oscilloscope. But if something go wrong with your PI project it is hard to solve problems without a scope.

You need to do some Google in Chinese to find basic instruction on how to use a scope. There are no significant difference between analog, digital or software scope regarding its controls and measurements.

[Qiaozhi]

I do not know ，I had to use the oscilloscope. Do not know how to measure your pulse.

Try using the BabelFish translator -> http://uk.babelfish.yahoo.com/
Enter the website address and select "English to Simplified Chinese" translation.

[chemelec]

I do not know ，I had to use the oscilloscope. Do not know how to measure your pulse.

Since your detector is Working somewhat, I would assume you have the correct Pulses from the 555's. I have Never seen a Situation to the contrary.
So a Scope won't really help you much.

Poor Sensitivity is probably Either your Coil or a Poor J-Fet for Q3.

You can do better testing on this with just a Voltmeter.

1) Do you have +5, -5 and -9.75 volts on the Appropriate TEST POINTS

2) Did you set the output, Pin 9 of IC6 to beween .2 & .5 Volts, using VR1?

3) With the Voltmeter Still Connected to pin 6 of IC-9, Bring a Pop Can Near the coil.
Now Tell me What Readings you have Without and With the pop can near the coil.

4) NEXT, REPEAT this test, but with the Voltmeter connected to Pin 6 of IC-10.
And Again, Now Tell me What Readings you have Without and With the pop can near the coil on this test.

Than Maybe I can help you better.

[yhl]

HELLO

All voltages are normal. IC9 SIX feet is 0.6V. JFET I use my 2SK30A, did not pick the wrong pin. Do not know can use it?

[chemelec]

All voltages are normal. IC9 SIX feet is 0.6V. JFET I use my 2SK30A, did not pick the wrong pin. Do not know can use it?

Some J-fets don't work as good as others.
And Some Batches Lots of a particular J-Fet can also give problems.

I Only use the 2N3819, And I test each Batch lot to Varify Performance before selling them.

Since you didn't buy the parts from me, it is Anyones GUESS to all your Problems.
Poor Quality parts can also result in poor performance.

You Also DIDN'T Answer ALL MY QUESTIONS.
So How do you expect me to help you?

But 0.6 is a Bit High.

And as to your Previous Statement Re: the LM317, It is ONLY Good, IF YOUR BATTERY IS FULLY CHARGED at 12.6 Volts MINIMUM.
If your battery goes below that, you lose regulation.

[yhl]

HELLO

2N3819 J310 can be used instead of it? I now have J310.

[chemelec]

2N3819 J310 can be used instead of it? I now have J310.

Sorry I Can't help you anymore.
You Never Answer my Questions!