Detector Build Stumbling Blocks

[Infamy]

Hi, I have a few issues I would like to raise here.

1) Components, as far as I am aware Silverdog is not supplying anything now and some essential components are either not easy to find or are expensive.
2) I was reading about the Crossbow Classic yesterday and how it is difficult to build, why is that?
3) The taking things for granted hole, your watching a video of a board being constructed and you have an oscilliscope screen but you don't see what everything is connected to and how the oscilliscope was set up. In fact this whole are of test equipement and how to use it seems to be an area where people if they are going to fail will. The little bit at the end you think people will know but if you are not from a electronics background you don't.
4) Haven't seen much on component testing.
5) Patreon website not sure that is the correct spelling but I pay 2 dollars a month to a guy there that does electronic videos. Maybe some of this stuff needs to go there so it can be covered clearly and in detail.

[GeoMax]

Hi, here some comments to your points.

1) The Crossbow PI does not contain any exotic or difficult to find components. All components are very common and cheap parts. However, it maybe depends from where you are from. Are you from Africa? Or from the Middle East? There might be a different situation in getting common electronic components.
2) What is so difficult in building the Crossbow? The step-by-step YouTube videos are excellent and made for not experienced builders.
3) In most of the oscilloscope screens, you can see the oscilloscope settings and the probe connection is very basic knowledge. The crocodile-clip (of the probe) usually connects to ground (GND) and the tip of the probe goes to the point where you want to measure.
If you are not familiar and/or know how to use an oscilloscope maybe you should check-out some learning videos on how to use an oscilloscope.

[Carl-NC]

In general, if you don't know much about electronics or how to use an oscilloscope then building a metal detector is not a good place to start. You should build some simpler circuits and learn the basics before trying to tackle something like a metal detector.

[Infamy]

What I want to understand is why people said the Crossbow Classic was a difficult build, what is it, what is in the fine detail.

I'm building two MPP beach detectors, having to source the components from multiple places. Have you checked the prices recently some of the ICs at my local electronics shop are 10 euros a piece!

Carl what is the raison d' etre of Geotech1?, serious question. It's a great resource no doubt about that with some outstanding contributions but maybe there is room for improvement, eg testing equipement how to use it where to find it.

Geomax I notice you helpfully mentioned ground, that's negative right in a PI detector?

A couple of places I use for help are eevblog and Mr Carlsons lab specifically those places because they know their stuff and explain in a manner which is easy to understand.

[Carl-NC]

The mission of Geotech is to provide technical information on metal detector design. There are lots of web sites & forums that teach basic electronics and how to use test equipment. Even though I recommend using those resources, Geotech still has a General Electronics forum where people can discuss the basics if they want to. Personally, I would rather not use my time to teach Ohm's Law or how to read an oscope when it's already been done a thousand times over (and better) elsewhere. But I also try not to ignore questions no matter how basic.

[GeoMax]

Hi Infamy,

to answer the your question to „ground“ correct, you first need to know what type of power supply you have and how is it connected to the circuit.
There are power supplies with +/- voltages, negative voltages or positive voltages. In general, you can say “ground” (GND) refers to signal ground.
In a circuit that connects to e.g. a 9V battery, the minus is here the “ground” and all other measurements are in respect to “ground” (minus pole of the battery).
If you have a power supply with e.g. +/- 5V like seen in many of the metal detector circuits, the “ground” does not refer to the minus (-5V). It refers to usually
0V (power supply 0V). Therefore, the measured signal can be in respect to +5V or -5V, depending on what signal you want to measure.

[GeoMax]

Hi Infamy,

You wrote “…Have you checked the prices recently some of the ICs at my local electronics shop are 10 euros a piece!...” Which IC is so expensive and from where are you from?

[Carl-NC]

You wrote “…Have you checked the prices recently some of the ICs at my local electronics shop are 10 euros a piece!...” Which IC is so expensive and from where are you from?

In general, IC prices have gone through the roof due to shortages. One of my favorites, the MAX412, is now over $8. It was $3 a few years ago.

[waltr]

In general, IC prices have gone through the roof due to shortages. One of my favorites, the MAX412, is now over $8. It was $3 a few years ago.

Some of the chips needed to build the products where I work have have become hard to get with lead time quotes of 50 to 80 weeks and double the price.
When looking for other supplies, we have been quoted $300 ea, min 1000 pieces for chips that did sell for $8ea.
Our Engineering team have been very busy re-designing circuits to use different chips.

[Infamy]

I keep reading the same stuff in some of the build videos, I'd like to build that detector but don't have an oscilloscope or can't use one. Taking a side ways look at this, my understanding is most of the detector kits and parts use to come from the UK, which given the dogs breakfast of Brexit, like a hole in the head as far as small business are concerned, means I don't know for certain there is a lack of supply, or increases in time and cost in sourcing parts . Anyone considering filling that void I guess would like to see a healthy demand. You know its the basic stuff that make a difference, as they found out at Nasa when one supply worked in mm and the other in inches.

I'm ordering 20 Crossbow Classic boards Rev. C I'm going to build 2 one with reasonable quality parts the other with high quality parts, and see how they perform. From what I've observed electrolytic capacitors are a basic component, a weak link that is over looked, as to quality and even voltage to be used. Should I use a 30 cent 1000uf 16v cap or a 1.90 Euro 1000uf 25v Panasonic FM/FC audio quality cap?

[Qiaozhi]

I keep reading the same stuff in some of the build videos, I'd like to build that detector but don't have an oscilloscope or can't use one. Taking a side ways look at this, my understanding is most of the detector kits and parts use to come from the UK, which given the dogs breakfast of Brexit, like a hole in the head as far as small business are concerned, means I don't know for certain there is a lack of supply, or increases in time and cost in sourcing parts . Anyone considering filling that void I guess would like to see a healthy demand. You know its the basic stuff that make a difference, as they found out at Nasa when one supply worked in mm and the other in inches.

I'm ordering 20 Crossbow Classic boards Rev. C I'm going to build 2 one with reasonable quality parts the other with high quality parts, and see how they perform. From what I've observed electrolytic capacitors are a basic component, a weak link that is over looked, as to quality and even voltage to be used. Should I use a 30 cent 1000uf 16v cap or a 1.90 Euro 1000uf 25v Panasonic FM/FC audio quality cap?

If you don't have an oscilloscope, and don't know how to use one, then you're just shooting yourself in the foot. It is not possible to build Crossbow (which is a derivative of Hammerhead) or most of the other PI detectors found on Geotech without one.

As Carl suggested, your first task is to learn some basic electronics. Build some other simpler circuits instead of jumping in head first at the deep end by building a metal detector. You would not be the first by any means to ignore this advice, but it always ends badly.

[Infamy]

If you don't have an oscilloscope, and don't know how to use one, then you're just shooting yourself in the foot. It is not possible to build Crossbow (which is a derivative of Hammerhead) or most of the other PI detectors found on Geotech without one.

As Carl suggested, your first task is to learn some basic electronics. Build some other simpler circuits instead of jumping in head first at the deep end by building a metal detector. You would not be the first by any means to ignore this advice, but it always ends badly.

You make too many assumptions.

I'm not asking about generalities but specifics.
Why was it difficult to build?
I've looked at everything I can find on it and I think its something to do as a second project, not as hard as it was, eg. less information black holes.

[Qiaozhi]

You make too many assumptions.

I'm not asking about generalities but specifics.
Why was it difficult to build?
I've looked at everything I can find on it and I think its something to do as a second project, not as hard as it was, eg. less information black holes.

I don't think I'm making assumptions. You actually wrote: "[I] don't have an oscilloscope or can't use one."
Without an oscilloscope your chances of success will be minimal.

Crossbow is only difficult to build for those with limited electronics knowledge, as there is no build document for that detector since it was never intended as a Geotech project.

[GeoMax]

Hi Infamy,

to answer your question of which capacitor to buy... Actually it depends very much were the capacitor is connected within the circuit and which voltage is applied across and/or possible to be expected.
Therefore, there are many types of capacitors for various needs in the market. The best would be following the recommendation by the circuit designer, if you do not have good electronic background knowledge.
Alternatively, you can upload the circuit diagram and let us know to which capacitor you are referring within the circuit. That might help to find the answer easier.

GeoMax

[Carl-NC]

Infamy, metal detectors are not difficult to build as long as you don't make a mistake. If you do make a mistake and don't have an oscope, then you're dead in the water. In any case, if you want to plow ahead I suggest you just start asking specific questions. On the caps GeoMax is right, "it depends." Ferinstance, the cap on the TX driver needs to be low ESR so a polymer type is best, and multiple parallel caps even better.