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Originally posted by green
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Indeed. That would appear to be the case.Originally posted by KRinAZ View Post
Either that, or you have the wrong value resistor fitted for either R33 or R34.Comment
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Thx, I verified again:
R33 is correct - & I measure 986 ohms across pin 2 of U9 & TP10 (measures R33, 1K resistor)
R34 is correct - & I measure 46.4K across pins 2 & 6 of U9 (measures R34, 47K resistor)
-4.96VDC on U9 pin 4 (VCC-)
+4.93VDC on U9 pin 7 (VCC+)
Battery pack power source 11.04VDC loaded - while powering the MPP
So it seems clear U9 arrived DOA, sigh, I will have to order one (or a couple) as I'm rural and there are no electronics components sources nearby (Radio Shack is 25 miles away but that store mostly has cell phones & does not have any of the IC's we use on this project). Will continue when I have the replacement...Comment
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Hi KRinAZ, from post #77 "I've discussed this coil with Don Bowers and suggested that if a number of us build these coils and would like a housing he could make housings for us. Currently it looks like the housing would be about 8.25" x 10.25" x 1", could be any mount we all agree on (he usually uses the 19mm Whites/Tesoro/Minelab mount tabs unless otherwise specified) We will need to get the cost per housing from him when we are ready, it appears they would be around $15 each (US Dollars) "
Count me in for two housings; I would prefer the Minelab 24mm spacing on the mount tabs. The wider base is stronger and is the standard for most Pulse Induction after market coils except for Whites. Spacers/washers can be used to fit with the 19mm shafts. He may be able to make both widths by having interchangeable tabs on his mold form. The inside height should be a minimum of 1".Comment
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Hi KRinAZ, from post #75; “I measured a 4' length of twisted # 22 Teflon wires with thinner insulation than yours. It measured 39pf on the capacitance meter. Good to know - think there's any coax that would be lower in capacitance?”
I use Blue Jeans LC-1 Audio Cable at 12.2 pF/ft, it gets close to matching twisted pairs. It is very durable and handles better than twisted wires. And it looks better. If you plan on making a number of coils it is cheaper to buy one long cable and cut to length as you use it. Just toss the two connectors that come already attached.
http://www.bluejeanscable.com/store/audio/Comment
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[QUOTE=Chet;198108]
I use Blue Jeans LC-1 Audio Cable at 12.2 pF/ft, it gets close to matching twisted pairs. It is very durable and handles better than twisted wires. And it looks better. If you plan on making a number of coils it is cheaper to buy one long cable and cut to length as you use it. Just toss the two connectors that come already attached.
http://www.bluejeanscable.com/store/audio/
Hmmm, thx for that Chet, seems like it would be some nice cable to try, I'll have to get some...[/QUOTE] .Comment
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OK, finally got parts from Mouser, swapped the bad TL071 for a new one, & step 8 checks out as working fine - my voltage swing at TP9 when adjusting Threshold is +/-4.1VDC, not 5 as the build doc says, don't know if that's an issue or not...
Anyway, I then finished step 9 and, in the words of Gene Wilder, "It's Alive!", yea! it works. Cool!
The audio sounds make me laugh but IMHO the audio is quite effective. I found some small 32 ohm speakers so I'm going to try one soon to see if maybe they aren't so loud.
This MPP is in the build doc form, I'm still using the 470ohm damping resistor (will get to that soon)..., no mods done to it yet but I think I may build a second one and mod it and compare the two...or I may just mod this one...
For the coil's initial air tests, it has no reaction to my hand - even when I have my hand completely wrapped around it - so the self shielding appears to work, will know more when it is in actual use scanning the ground...and as for detection pattern - detection distance is surprisingly uniform all around under the coil and to the sides. I expected a clear cone shaped detection pattern but the cone effect is actually very slight - perhaps a .5" (13mm) deeper detection in true center, and it is very easy to pinpoint a target with the nose or heel of the coil where it is more pointed. I look forward to making a video of it in use on the ground when I get to that point with this project...Comment
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OK, so now it's time to figure how to put it together into something I can use in the field - needs a box to hold the electronics, a pole system to connect the search coil, arm rests, etc. Curious what others have used to complete their project...
I picked up a Whites Classic ID for not much - thought I could remove the electronics and use it for this project - but I made the mistake of trying it out in the field and found it to be quite a nice treasure hunter, I really like it - so now I don't want to make it a donor...but something like that seems like it would work well...Comment
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The voltage swing of +/-5V mentioned in the Build Document is only a guide. The TL071 rails out at about 4V, so your voltages are fine.Originally posted by KRinAZ View PostComment
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You can buy a stick for $48 (ouch) http://www.ebay.com/itm/271609965612...%3AMEBIDX%3AITOK, so now it's time to figure how to put it together into something I can use in the field...
And Coil Housing for $14 http://www.ebay.com/itm/121469795547...%3AMEBIDX%3AIT
And a box for $15 http://www.ebay.com/itm/OtterBox-Pur...item19f156f030
Or look for a cheapo detector. I got a tracker IV for $60 brand new planning on using the stick for other MD'sComment
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Try this -> http://www.whiteselectronics.com/space-saver-rod-kitOriginally posted by Silver Dollar View PostComment
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You could use an ice scraper as a stick;
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I got a tracker IV for $60 brand new planning on using the stick for other MD's
Sven did BH in GMT housing. http://compass-metal-detector-forum....td7600844.html
nice done...Comment
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I bought some GMT housings. They were about $25 each;
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