Help with building CCO?

[maikl]

Not according author of both:

CCO:

"With this circuit, I obtained a one-tone shift in an AM radio speaker at 15 cm (6 inches) with a 27mm (1 inch) diameter coin."

BB:

"If well adjusted, it will pick up an old English penny at 150mm (6”)"

The same depth in air. I suppose that author has build both not only one as you.

Generaly speaking it is hard to get something from nothing. And one chip detectors are pretty nothing (even 12V supply was used). With mine BB I can easily detect 30mm silver coin at 15cm in air but in soil (in my testing plant) it is hard detectable deeper than 7-8cm.

In this pdf. author says the following:"""The circuit is presented merely as an experimental idea. With some care, an old Victorian
penny should induce a clear shift in tone at 160mm in a crystal earpiece, and a perceptible shift in
tone at up to 250mm""". It is at par with IB simpler detector that has far more parts of the CCO.So the author has given only as an idea of experiment in desire to further develop.But no one is interested in something new.Here we discuss the models that are 10-30 years old.

[maikl]

I forget to say what the author says to BB:"Range: Up to 6" for 1" dia. coin (sure bet 5")".Which means BB (150mm-125mm) and CCO (250mm-160mm).But we are not little children that convinces.It is important that the Serbian national team beat Germany with 1: 0.

[nabiul]

I am using a crystal earpiece, but I don't know the impedance. Is it possible to damage it from applying too high of a voltage?

Do you know what the voltage reading on the output of the TL071 is? Mine showed something like 8 volts, which is high I assume for any kind of audio device?

[maikl]

I am using a crystal earpiece, but I don't know the impedance. Is it possible to damage it from applying too high of a voltage?

Do you know what the voltage reading on the output of the TL071 is? Mine showed something like 8 volts, which is high I assume for any kind of audio device?

To do the simplest detector in the world must have a basic knowledge of electronics.

[nabiul]

I do have a pretty ok understanding of electronics, but unfortunately bad equipment.

It works, but I can just barely hear the tone. I am only reading about 1.2 volts across the earpiece while using approx 11.5V source, and only when I tilt the circuit board, I think there is a bad solder joint or a broken wire. I used pretty old wire to build it so it's not out of the question.

Now the important part, do I try to find the faults, or do I just buy another $4.00 of parts next week and rebuild it....hmm.

[nabiul]

I think I've fixed the bad connection, but something strange is happening. The circuit seems to work better when powered by 9.5 volts instead of 11.5. At 9.5 volts the earpiece was much louder than at 11.5, I was measuring something like 2.3 volts across it. I was also able to set it up so that a clear tone is heard when a mixed brass and a mystery metal coin was brought near.

Still have some playing around to do before I permanently fix things.

[mikebg]

To do the simplest detector in the world must have a basic knowledge of electronics.

To design the simplest detector in the world, a designer must have a basic knowledge of electronics. Rev Scarborough should learn what is operating point of an opamp and how it is achieved. His designs are in category BAD CIRCUITS having undefined operating point.
Maikl, Congratulations on your victory over Germany.

[nabiul]

Does any one know how to control the output volume of the TL071? Perhaps some way using the offset pins 1 and 5? Otherwise I'm going to have to put another op amp on the output of this thing.

I don't know if it's because of my bad coils, they aren't the full 50 turns, ran out of wire so I reduced them to around 44 or so.

[maikl]

To design the simplest detector in the world, a designer must have a basic knowledge of electronics. Rev Scarborough should learn what is operating point of an opamp and how it is achieved. His designs are in category BAD CIRCUITS having undefined operating point.
Maikl, Congratulations on your victory over Germany.

Thomas Scarborough excellent knowledge of the basics of electronics. He has designed many different things in the field of electronics. Here are some of his personal design classic IB metal detectors (working on the old principle TX (transmitter) and RX (receiver)) : EPE Bounty Treasure Hunter (160mm-240mm detects old Victorian peny), matchless Metal Locator (110mm-150mm), Minimalist Induction-Balance Metal Detector(Carefully built and aligned, it will clearly pick up a tiny 15 mm dia. brass coin at 70 mm in air, or a 25 mm coin at 120 mm).But what is the problem now? Constructors (with little knowledge of electronics) experienced difficulty with the setup are unable to do it.And the man is more and more simplified detectors.And in the end lost the depth of detection.Therefore, the author of Thomas Scarborough invented something new CCO metal detector(remarkable simplicity that can make it any beginner), that can be measured in the range of the average IB. CCO in principle is a "DOUBLE BFO". BFO and BFO is of him can not be expected much,even if he was double BFO.I heartily recommend all beginners to do CCO.If someone does not believe a done ETI 561 and to do the CCO.Or make EPE Bounty Treasure Hunter.And you'll see the difference "In every way"."mikebg" l will not ask you to tell me some of your personal design.I ask you: What do you think of "turkey Tarsos VLF detector" detects coin to 400mm in the air and easy to build (only two IR and 6 transistors).It is a bit different than the standard VLF metal detector: TX = 12 + 136 turns (no Faraday shield) and RX = 157 turns(a Faraday shield) "DD Form" .Probably his sensitivity comes from the fact that the Faraday shield has the not TX coil.I know that this simple and easy and quite efficient designs represent a threat to the industrial metal detectors.Therefore, discussing the models 10-30 years old and stands in the place(stuck in a time machine). mikebg interested in your opinion about "TARSOS".

[mikebg]

Thomas Scarborough excellent knowledge of the basics of electronics. He has designed many different things in the field of electronics.Therefore, the author of Thomas Scarborough invented something new CCO metal detector(remarkable simplicity that can make it any beginner), that can be measured in the range of the average IB. CCO in principle is a "DOUBLE BFO". BFO and BFO is of him can not be expected much,even if he was double BFO.I heartily recommend all beginners to do .. mikebg interested in your opinion about "TARSOS".

Maikl, You drank too much around your victory over Germany, so your last post is full of unreasonable claims. I will answer all your questions once I'm sure that you understand me. To prove that you are sober, please send me your calculation of the operating point of the operational amplifier in mentioned design of rev Thomas and write the block diagram of TARSOS. I think that you have more knowledge than the rev.

[nabiul]

To be fair, Rev Thomas didn't make the circuit with the opamp, his original was the one that used an AM radio. Some one else modified the circuit and republished it, one Barnaby Brown.

What is worrying is that the guy who republished it, used word by word of Rev Thomas original post on some forum.

I don't understand why the coil circuit and the constant frequency circuit are used as the positive and negative inputs of the opamp. Isn't one of the inputs used for volume control purposes? Bah I have to learn about opamps and modify this circuit.

[mikebg]

To be fair, Rev Thomas didn't make the circuit with the opamp, his original was the one that used an AM radio. ....
I don't understand why the coil circuit and the constant frequency circuit are used as the positive and negative inputs of the opamp. Isn't one of the inputs used for volume control purposes? Bah I have to learn about opamps and modify this circuit.

Nabiul, the most important stage in the design of a metal detector is the composition of its block diagram . If the block diagram is composed correctly and the size of signals at the input and output of each block are determined correctly, good results will be obtained even when using outdated methods such as transistor amplifiers and audio displaying by AM radio.
However, if the block diagram contains an amplifying block, and you do not know how to be its gain, and what should be its operating point, if you save important resistors in order to simplify the circuit diagram, it is ignorance. Unfortunately, ignorance is shown by editors of magazines who have published the BAD CIRCUITS of rev Thomas.

[yhl]

cco metal detectors you can use 9V battery?

[mikebg]

cco metal detectors you can use 9V battery?

Yes yhl, but you should create 4.5V operating point in output using two resistors for bias. Post me an email with attached your circuit diagram, to show you the correction.

[maikl]

Maikl, You drank too much around your victory over Germany, so your last post is full of unreasonable claims. I will answer all your questions once I'm sure that you understand me. To prove that you are sober, please send me your calculation of the operating point of the operational amplifier in mentioned design of rev Thomas and write the block diagram of TARSOS. I think that you have more knowledge than the rev.

Hi mikebg.Threads in Forum , Schematics: "Popular Electronics, Feb. 1969". I'm not even realize at first.At first, I thought you had a proposal for improving the design.But later I realized that you changed so much that it would not be more CCO metal detector. In post # 39 something trying to persuade you.I have made the CCO and the CCO with a TL071 integrated circuit and capacitor of 1nF (with the help of AM radio).Work great just as the author says.Excellent sensitivity and discrimination. Is my English so bad in the rank of "drunken Englishmen," or whatever???