How can i make a metal detector

		Quote:			Posted by xavier
	Hi Goldigger LM741 and NE555 what would we do with out them. I don?t use ceramic caps I had a few drifting circuits and at first did not know what it was then discovered that the ceramic cap's were the culprits now I only use good quality cap's Mylar is my favorite and the nice thing is that they are widely used in all sort of electronic devices so it's just a question of collecting what ever don?t work and recuperate the caps  I just love doing that. By the way I posted a small article on how to make your own pot core did you see it? I would like to know what you think of the make shift plan in fact I should like you to try it and let me know how it compares with the bought pot core see I don?t have any to use for testing and to tell you the truth I?m not sure how to do the testing. I have downloaded some nice sine wave generators if you like I can post them for you there is one in particular that I?m not sure if it?s any good for this application it just looks to dam easy here it is. Best regards Xavier

That is different, but not as simple as some I have... I have 2 volumes of the Encyclopaedia of Electronics... lots of good stuff but dated. I find the latest Volume to be a bit high priced.

I answered the post, the one about making your own pot core, what is it and do I really need it? As for setting it on a magnet, I have a magnet that is about 8 or 9 inches across, 1.75 inches thick and weighs about 10 pounds.... shall I interpret that into metric? 

I can not do things like that now, we have about 61 cm of snow, just had 2 snowfalls of 30 cm... it will settle to about 30 cm, after a while. It is not real cold, -6 to +4, but not suitable for epoxy work. It must be nice to live where it is warm all the time! 

I am at about 56 degrees N and a hair over 120 degrees west, we do get warm pacific air, off and on (called "Chinooks," which are adiabatic heating,) with blasts from the deep-freezer, in between. You need at least 20 or 22 deg C, for good results with epoxy. If you take a look with Google Earth, I will wave. 

Eventually I will get some heated shop space made, "den I vill show de vorld." 

I would never suggest using ceramic caps  except for bypass, one unique feature... if you incorporate a ceramic cap into an oscillator circuit, in such a way that you may apply a modulating voltage, (like a serial data, on/off, binary voltage) you will have an FM oscillator, or FSK serial data generator! No, what I said was pick a positive/negative/zero temperature coefficient, to correct frequency drift. All capacitors/resistors have a coefficient rating. Ceramic are just the worst! 

I built a varactor tuned 80 meter QRP, one time that drifted about 1kHz in 15 minutes. To stop it, I experimented with coefficients, until I got it down to about 200 Hz per hour... not crystal quality but fairly stable. Since then, I have discovered PLL controlled VCO's. My fav is PLL02A, it has 511 (512 - 1,) channels spaced by derivation of the reference frequency and good to 5.5 mHz. 

To get 1kHz channels: 1024 X 0.001 mHz = 1.024 mHz reference xtal, the offset xtal depends on what band you want... 40m as 6.999 mHz to 7.501 mHz use a 6.999 mHz xtal, or a 7.000 mHz xtal pulled 1kHz. And fine tune by varying this xtal +/- 500 Hz.... no more drift. for 80m, here, 3.500 to 4.000  mHz a 3.5 mHz offset xtal gives 3.499 to 4.000 mHz 

The same idea could be incorporated into metal locators to get incrementation of the operating frequency, and only 3 or 4 (maybe 8?) "channels" of, say 5 kHz? I still like 30.76 kHz xtal and a CD4040 to get all kinds of frequencies. 

I just realized how to make a simple frequency counter with CD4017's! For 7 digits, 7 CD4017's would be required.... I have to go sketch! 

goldigger



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		Quote:			Posted by xavier
	That re-mind's me I have to add a CD4040 to my components list I did how ever order 2 * CD4017 now I will have to get 5 more and an LCD display I'm preparing my self for the schematic . Over here it gets so hot that one drop of catalyst and a few seconds latter you have a blob of chewing gum dam thats iriritating

What no Acacia gum, or is it that the needles attack? Yummy stuff, and good gum, for a while. You must have lots of them there. Acacia trees, that is.

I do not know if you will like my idea for a frequency meter, I got the idea from an OOOOLD, Don Lancaster article, in Pop Tronics, that was published around 1978! Ooops!

I have 4 "pages" in the schematic drawing software! One of them is just to explain how to read it! The idea uses 6 CD4017 decimal counters, so each one has 10 LEDs, over which you place a translucent, corresponding number. That makes 6 columns of 10 LEDs. The bottom LED reads 0, and the top LED reads 9, with all the other numbers reading accordingly (10 translucent numbers,) I had it designed then got to worrying about eye persistence, so redesigned for a frequency snap-shot or continuous run.

Neatness is smallness, of course, if you get the 10 LED strips for the 3914s, and can use tiny numbers, it will be neat, but you will have to squint!

The lowest number is 10 Hz (10Hz clock,) the highest is the highest mHz that a CD4017 will handle, in single mHz. If the CD4017 will do as good as a CD4040 in frequency, it should read up to 9.9999 mHz. I have seen some circuits that use a CD4040, but they are complex, this is simple and no 7 segment displays, no 7 segment decoders, but no LCD unit either. (As with the PICs.) A CD4040 would be simple with a couple of proms, maybe.

To get 10 Hz, I needed a 74C92, but they are archaic! So I designed, using a down counter of 12 counts (programmable,) with a CD4029, dividing 30.72 kHz xtal by 12 then by 256 (Q8) with a CD4040. There are more than 100 uses for a dead sheep.

I will have to learn C+ before I can programme a PIC to read a true bridge and calculate voltage value, using the built in ADC, not frequency.

goldigger

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		Quote:			Posted by xavier
	Hi Goldigger   It sounds like a very interesting project that you have there  I?m also working on the problem I have found quite a lot of schematics on the net some good some not so good and I found that I too will have to learn how to write with C+ but that?s all in the day?s fun the thing is to have an LC meter that is accurate not that I need the capacitance meter at the moment but if I can do both in one why not the most important for me at the moment is to be able to have an inductance meter. I have spent the weekend making a power supply that is ripple protected and variable the one side of the output is just variable and the other is +x ?x with virtual ground I can adjust it from 1.2V to 12V with a current of up to 1.5A I used an LM317T  with a 1.2A fuse for extra protection but it?s not necessary as the LM317T comes with it?s own internal short circuit protection it?s working fine just that the pot that I have at the moment is a 50K pot and I need a 5K pot I am sure that there is a way to get by with the 50K pot but I just don?t know how yet and that brings me to another problem that I have. My friend has a canoe that he runs on a 12V battery has some 40A relays(consumption max=30A) with a switch to select the different windings on the motor allowing for the different speeds he has a solar panel that helps re-charge that battery as he navigates on the canal the thing is that the relays get very hot due to oxidation caused by the salt water and they get sticky causing the whole thing to fail it works very well when the relays are cleaned up but only for a while now do you perhaps have a schematic that could control that motor in place of those relays? I have had a look on the net but I only found one diagram and I would like to have your opinion too on this one I know this is not Thunting material but I just don?t have any one ells to ask. Best regards Xavier

I would have to see a diagram of the relays and motor, and an explanation of how they work, but I also have an idea that could save some grief! Solid state relays can handle loads of amps and they can be totally enclosed.... any wiring can be done inside of garden hose, with the rubbery washers, this will seal out gas and salt water, both.

I have a favourite goody store in a town, 85 miles away that has all kinds of solid-state relays, some are solder lugs and some are screw terminal.

How does that sound? If he can get  solid-state relays, he can exchange for the contact type, as he will know the ins and outs of the circuit. It seems to me they will work on just 5 volts, too, and the max voltage will be listed on them. Basically they work like huge SCRs, but they only work as long as the voltage is applied to the trigger, just like a coil relay.... hey, no coil losses either!

goldigger

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		Quote:			Posted by xavier
	That sound like a good plan    I will tell him about this tonight when I see him. By the way how are you coming along with you aerial setup?  : Xavier

Aerials are shut down until spring! We have had a total of 4 feet (120cm) of snow, in the past 3 weeks... the first 2 feet (60cm) was almost gone when it hit  again! We get pacific lows, coming in over the mountains that either rain or snow, and give adiabatic heating. (Called Chinooks.) They are worse in El Ni?o years, where the westerlies fail, in the Pacific and all that hot water flows back east! 

I want to get a small holiday trailer, before I build aerials, so I have a home for radios! Next summer, I hope.

Next summer, I have to get some gold, while it is over $1100US! How to get it all done?

goldigger

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Xavier, we shouldn't tease those Northern Hemisphere folks.

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