BARACUDA-Legend-1

[Wilson]

Porkluvr Olá, eu tenho que ajustar o resitor Damper para corrigir ok.

[porkluvr]

Wilson, I don't know if you want to read this or not, but I think your scope display indicates a problem. Look at Mohandes' scope shots in #904. That is more like what your rx should look like. Problem is, I do not know what you need to do to fix it.

Q: What was wrong before, why did you replace NE5534 with OP27??

Mohandes, 904 is almost good (flyback is really slow but at least the rx amplifier is not ringing). You do not want to have what you drew in 909.

[Wilson]

Mohandes Hello, I'm sorry I made a mistake in stating for you to use the channel of the oscilloscope in AC. I use DC Corrigo I unfortunately can not edit the text after a while.
I usually use the oscilloscope to almost all measurements, follows a photo offset adjustment marked with a blue line. I make mistakes anguns using the translator because I do not speak English.

[mohandes]

am i say right about the above pic,is it possible the problem for sound of that?????(my speaker have not sound)

[mohandes]

Let me think about this...

Please put your oscilloscope on DC coupling and please LEAVE IT THERE. I was right when I told you that in a PM. Ignore anybody telling you you need the scope on AC coupling. That is a bone-headed idea.

Why didn't I think of this yesterday... if you were nulling an IB coil then you could use AC coupling, but you are not. Use DC coupling when you are attempting to null a DC voltage. You cannot do it the other way.

my friend i think my problem in pin6 ne5534.
i can not set 0volt by pot 25k , why?i use pot 1k ohm 3 watt to find the best set point .
when coil voltage near 70 volt , pin6 ne5534 is 0.13 volt and can not set it.and when i return the pot this voltage goes higher near0.4volt ( my means ne5534-6).AND LARGER out put voltage that i can see in the oscope is near 140 vgolt , i use irf9640 and tip127 and both of them are same voltage
the important thing that when i measure coil voltage by multimeter , it is between 0.02 volt and 0.35 volts (correct voltage is 2.9 volt tht says Apberg)
summary :
i think this wave should like under pic ,please tell how i adjust like it:

[fabienmartin]

Hi. this pi can detect a bronze metal 20*20 in 2 meter in the underground?

[Old cart]

All, take a look at the following: http://www.testequity.com/static/86/

This is a very good collection of basic scope info. I think you can also get these at tek.com in foreign languages. I was a technical salesman for Tektronix for 31 years. I have taught thousands of customers how to use a scope properly. It is not that hard to learn and these documents provide a good background. As far as I am concerned a scope is essential for any design and optimization work. It doesn't have to be Tektronix. Most any scope 20 Mhz or better will do. it should have at least two channels. i do not recomend PC based scopes. You wil also need at least two x10 probes for low capacitance. A x1 probe wil be helpful as well. If you have limited budget <$1000 USD avoid digital scopes. The low priced ones has severe limitations regardless of brand.

Metal detectors in particular require waveform observation.
Last night I optimized an ancient Garrett XL 500 for low conductivity. I was able to improve depth from 21 to 27 cm on a nickel by reducing minimum pulse delay and adjusting first stage offset.mwithout a scope I would not been able to observe some clamping diode funnies that were going on.

[bion]

Hello everyone. Before constructing this metal detector wanted to know if I need oscilloscope to the settings or can be adjusted with the tester?. Ask because I have no oscilloscope. Thank you very much.

[porkluvr]

Let me think about this...

Please put your oscilloscope on DC coupling and please LEAVE IT THERE. I was right when I told you that in a PM. Ignore anybody telling you you need the scope on AC coupling. That is a bone-headed idea.

Why didn't I think of this yesterday... if you were nulling an IB coil then you could use AC coupling, but you are not. Use DC coupling when you are attempting to null a DC voltage. You cannot do it the other way.

[mohandes]

hi
ok!
but i can noy set pin6 5534 on 0 VAC.
look pic under
pin1 lf412cn and 5534-6
another pin2 40106 and 5534-6

[porkluvr]

Mohandes, will you please THINK. If you are already thinking, then please think just a little bit harder? (No, I take that back... would you please try to think a whole lot harder?)

When you select AC coupling, a capacitor gets inserted in series between your probe tip and the oscilloscope's signal amplifier. Any direct current (DC) voltage will be rejected. For instance, if you have 0.8V alternating current (0.8VAC) riding on top of a 500V direct current voltage (500VDC), with AC coupling selected, you would only see the 0.8VAC. You would very possibly be completely oblivious to 500VDC that is also present. You might not even know that a potentially lethal voltage was present (except that your oscilloscope might fry, and/or you might get a nasty shock if you were un-lucky).

If, on the other hand, you used DC coupling to view that same signal, you might measure a 500VDC signal and be completely unaware that there was also 0.8VAC present. The same thing goes for when you are using a multimeter. If you set your multimeter on a 500VDC (Direct Current) scale and plug the leads into a 220VAC socket, the meter would essentially read 0V. Hmmm, would that mean that 220VAC was not present? NO it would not, (touch it, and find out for "pretty sure"). There is a capacitor used in the AC measurement section that blocks any DC voltage present. DC might be there, but your meter will not let you know, if set for AC measurement.

You would need to have the oscilloscope (or multimeter) set to a suitable voltage scale before you would be able to discern either of those two voltage components. The point I am trying to get across to you is that it is very unlikely that you would be able to measure both of those two voltage components at the same time, even though they are both there at the same time. AC and the DC voltage components, when they are combined, very often each need to be looked at individually before you can have understanding. You should ask yourself, "have I seen everything there is to see"??

Now, I used 500VDC and 0.8VAC in my example because their differences are vast and obvious, but even if the voltage components were a more realistic 5VDC and 0.8VAC, the same rule applies: it is often necessary to take more than one look at a signal before you can have any understanding.

So, when Wilson told you to set your meter, or scope (or whatever) to AC coupling, that is because you do not need to be concerned with any DC voltage that is present, you are only concerned with the AC signal component (AT THIS TIME).

[mohandes]

Rock and roll.

i am not good dancer.
i put my waves tonight and you look at them

[porkluvr]

Rock and roll.

[mohandes]

Hello Mohandes, you must adjust the zero on pin 6 of the IC NE5534 and not in the LF412 pin 1, the adjustment should be done with the coil connected and away from metals. Adjust the trimpot ofset IC NE5534 with a multimeter measuring AC in scala pin 6. You can also use the oscilloscope, centralizing the cycle positive and negative, that does not mean that the pulses from pin 6 to disappear.

hi wilson
thanks , i try too that but in AC show 0.75volts and on DC 0.335 volts (not change value on ac or dc points when i measure by multimeter)
why do put on AC point the multimeter and not DC point?!!
regards man and sorry me.

[Wilson]

Hello Mohandes, you must adjust the zero on pin 6 of the IC NE5534 and not in the LF412 pin 1, the adjustment should be done with the coil connected and away from metals. Adjust the trimpot ofset IC NE5534 with a multimeter measuring AC in scala pin 6. You can also use the oscilloscope, centralizing the cycle positive and negative, that does not mean that the pulses from pin 6 to disappear.