making my own pinpointer, Ferrite rod size?

Yousername · Sep 22, 2013

So im thinking of making my own pinpointer gonna head into town either today or tomorrow to price out a soldering iron and the metal detector soldering kit at radio shack, The ferrite rod that comes with the MD kit is of decent size, bout 2 inches long and half inch or so in diameter, my question is what size ferrite rod should i use in order for it to be as strong as if not stronger then the garrett pro pointer? Would the one that comes with the kit be good enough or do i need to buy a bigger one? The one that comes with the kit is big enough to wrap the copper wire around 163 times(i built one yesterday at my colleges alumni thing as i was showing people how to solder.) I figure 15bucks or so for a soldering iron at 10-20 bucks for the MD kit and another 10 or so if i need a bigger ferrite rod would be better then spending 120 on a propointer.

HarveyH48 · Sep 22, 2013

There is a whole lot more to it, than size of the core, and number of windings of copper you put on it. Might help some, but not enough to make a huge difference. Haven't built kits in years, but most of the ones in the past, were technically functional, but not exactly useful. They are mostly learning tools. You learn to identify parts, pins, polarity, soldering, and usually some troubleshooting/testing skills. Just guessing, but there is probably little range to the kit, almost touching. To get more range, you will need a more powerful transmitting circuit, or more amplification in the receiving side, little of both, probably. You'll need to filter what is received, so it can operate stable, at higher power.

Without a schematic, anyone who could actually give detailed help, would be just guessing. A link to the kit online, would help from the description. Radio Shack use to have manuals online for everything the sold, not sure if they still do. Was never a huge fan, high prices, poor quality components, but pretty much the only place you could go to get parts in town, if you didn't want to wait days to order them. Worked out about the same, adding shipping to the price. It's been decades, things change.

Yousername · Sep 22, 2013

HarveyH48 said:
There is a whole lot more to it, than size of the core, and number of windings of copper you put on it. Might help some, but not enough to make a huge difference. Haven't built kits in years, but most of the ones in the past, were technically functional, but not exactly useful. They are mostly learning tools. You learn to identify parts, pins, polarity, soldering, and usually some troubleshooting/testing skills. Just guessing, but there is probably little range to the kit, almost touching. To get more range, you will need a more powerful transmitting circuit, or more amplification in the receiving side, little of both, probably. You'll need to filter what is received, so it can operate stable, at higher power.

Without a schematic, anyone who could actually give detailed help, would be just guessing. A link to the kit online, would help from the description. Radio Shack use to have manuals online for everything the sold, not sure if they still do. Was never a huge fan, high prices, poor quality components, but pretty much the only place you could go to get parts in town, if you didn't want to wait days to order them. Worked out about the same, adding shipping to the price. It's been decades, things change.

Thanks for the info, looked online for "Radio Shack Metal Detector Soldering Kit" and couldn't find it sadly, one thing i do remember is it has 2 ceramic capacitors a 322 and a 200 something, says to test them both out and use w/e works best, also i remember when looking at the page for the resistors it said something about 10k OHMs and 100k OHMS, also the "MD" that you build has a sensitivity adjustment, what i figured was buy it, build it(just found out i have a soldering gun so no money spent there) and test it out, if it gets better range then my fisher pinpointer great! if not then monkey around with it and post it here on the forums, im not knowledgeable on circuits and all that happy horse poo, but its something interesting that i do wana get into, i'll try and look again see if i can't find the kit online and i'll post the link if i can find it.

EDIT: can't find the one from radio shack but this one looks exactly like it http://www.kitsusa.net/phpstore/html/VELLEMAN-K7102-Metal-Detector-soldering-kit-554.html don't know about a schematic for it but this is all i can find.

HarveyH48 · Sep 22, 2013

Found the manual, pulled the schematic. Pretty much as expected, very minimal circuit. You really might reconsider the soldering gun, most get way too hot, not really intended for circuit boards. A 25 watt iron should be okay. Check the gun, could be low wattage, like an iron, just gun-style, have seen them that way. Excessive heat destroys semiconductors, like transistors and diodes. Not real good for capacitors either. You can clip a heatsink (alligator clip, hemostat) on the lead you are soldering, to help keep it cool. Try to get the lead soldered quick, if you go with the high wattage gun.

Yousername · Sep 22, 2013

HarveyH48 said:
Found the manual, pulled the schematic. Pretty much as expected, very minimal circuit. You really might reconsider the soldering gun, most get way too hot, not really intended for circuit boards. A 25 watt iron should be okay. Check the gun, could be low wattage, like an iron, just gun-style, have seen them that way. Excessive heat destroys semiconductors, like transistors and diodes. Not real good for capacitors either. You can clip a heatsink (alligator clip, hemostat) on the lead you are soldering, to help keep it cool. Try to get the lead soldered quick, if you go with the high wattage gun.

alright, thanks for the info. Guess i'll just buy the propointer but still might mess around with some boards and try to build one for !!!!! and giggles.

HarveyH48 · Sep 22, 2013

I've always had fun building stuff. It's challenging and rewarding. It's always so cool to get them all assembled, power them up the first time, never knowing if it's going to work or not. Still have some failures, after all these years, but it's not a total loss, have to go through and figure what went wrong.

Yousername · Sep 22, 2013

HarveyH48 said:
I've always had fun building stuff. It's challenging and rewarding. It's always so cool to get them all assembled, power them up the first time, never knowing if it's going to work or not. Still have some failures, after all these years, but it's not a total loss, have to go through and figure what went wrong.

was told the garrett PP has a range of 1.5 to 2 inches and found this schematic says it has a range of a few inches, don't know, may try to figure this out since i have no idea how to read schematic and once i figure it out build it and test it out, if i can build it cheap enough might not need to buy the PP if its as strong.

HarveyH48 · Sep 23, 2013

Here's a link to more information on that project.

http://chemelec.com/Projects/CS209/CS209A.htm

I don't do surface-mount components, and he says the traditional package is tough to find anymore.

It's a great site for electronics project, pretty easy to understand. He has a dozen or so other metal detecting circuits as well.

John in NC · Oct 2, 2013

The length of wire used and the size of the wire for L1 and L2 on the ferrite rod will make or break it. I would experiment with 22 gauge wire for L1 and about 30 for L2. If you know the resistance and impedance values of L1 and L2 it will help. L2 is going to be your receive coil. Use coated magnet wire for the windings and you might even experiment with 1 L1 and 2 L2 windings to make it more sensitive.
John

making my own pinpointer, Ferrite rod size?

Yousername

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HarveyH48

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Yousername

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HarveyH48

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Yousername

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John in NC

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