Barracuda Legend Kit Problems

[jladre]

Just a note re the 40106 operated from Ground (0 volts) and -5 volts...

The IC itself will operate from 3 to 18 volts (although some manufacturers max voltage may be as low as 15 volts)... more importantly, most datasheets that actually bother to provide the maximum differential (between input voltage and supply voltage) quote 0.5 volts...

In effect this means that pins 1, 3 and 5, exceed the maximum voltage differential for the device... basically they could potentially fail...
Of course modifying R17, R18 and R19 so that they are connected to Ground would also modify the timing so values might require tweaking but it's probably better to operate the 40106 at +/- 5 volts instead (tweaking may still be required)...

Having said that, I have used 40106's for level shifting but only from 3.3 to 5 and vice versa and so far I haven't had one fail...

Mike

In my bara i dont have issue in motion problem. Just be sure that all contacts from board to coil is clean and tight.

[Michaelo]

Just a note re the 40106 operated from Ground (0 volts) and -5 volts...

The IC itself will operate from 3 to 18 volts (although some manufacturers max voltage may be as low as 15 volts)... more importantly, most datasheets that actually bother to provide the maximum differential (between input voltage and supply voltage) quote 0.5 volts...

In effect this means that pins 1, 3 and 5, exceed the maximum voltage differential for the device... basically they could potentially fail...
Of course modifying R17, R18 and R19 so that they are connected to Ground would also modify the timing so values might require tweaking but it's probably better to operate the 40106 at +/- 5 volts instead (tweaking may still be required)...

Having said that, I have used 40106's for level shifting but only from 3.3 to 5 and vice versa and so far I haven't had one fail...

Mike

[6666]

I have more joy experimenting with components on the Suf Pi longboard as the holes are normal there.

Use pcb pins and just solder component on to pins. or use machined IC pins as socket.

[dfbowers]

Hey guys.
I have been following this thread for the last few days. This thing about the coil motion problem seems all so familiar! I have built three Silverdog kits so far. The first one worked like a champ for a couple of season. Then it died and for the life of me I could not resolve it. I built a second. It works well but suffers badly from coil motion problems. I used it at the beach last summer well away from electrical noise sources. The coil is shielded and potted. Same coil as Baracuda #1. I tried matching resistors and FETs without success. So.. I built a third paying careful attention to detail. Same problem : / I cannot offer a solution at this point. But can only suggest that it's not just one or two builds with the same issue. I have pretty much ruled out electrical noise and unpotted or unshielded coils as the sole source.
Don..

[Polymer]

Hello raygdunn,

Don't doubt your part replacement skills. The holes on the Baracuda PCB are too small and unsoldering parts off it is a real f*#?$~ pain.

I have more joy experimenting with components on the Suf Pi longboard as the holes are normal there.

[Old cart]

Thanks for the advice guys. I have a solder sucker, but I suspect the nozzle is too large.. And not very heat resistant. Time for an upgrade I think☺

I've not been very successful with the solder wick in the distant past. Time I tried it again.

Good point about the drilling. I was enlarging the holes very slightly.

Ray

I use solder wick and a toothpick to clear the holes. Put the wick down and press firmly with the hot soldering iron. It will suck up most of the solder. Then heat the component one lead at a a time and gentlly pull on the lead with needle nose pliers. Takes some practice but works fine once you get the hang of it. Might practice on an old scrap board if you have one. For IC's many just cut the leads then extract the pins. FLUX is a godsend! But don't use the acid type, use the rosin type.

Your timing looks fine except the 2nd pulse is too wide. The pulse controls how much earth field cancellation you have which keeps the detector from sounding when you move the coil in the earths magnetic field. You could parallel that resistor then adjust your 100K pot for 44uS. Disconnect and measure the pot then solder that value of fixed resistor parallel to the one on the board. No need to remove the resistor on the board.

An even better method might be to adjust for 44us then wave a small magnet ceramic magnet near the coil, adjust the pot for minimum response to the moving magnet. I think it is better not to use an iron magnet.

Then do the remove, measure, parallel thing.

If you get this right there will little or no response to to the moving magnet.

The 5534 0 adjust is not for this. It looks fine now. Once we get the earth field cancelled then we can optimize the damping resistor and the 0 adjust to give the fastest recovery. This is in direct correlation with the narrowest negative going pulse. Fast recovery is the key to detection of small gold.

[raygdunn]

I use to replace ICs on home computer everyday with a solder sucker. The holes on Silverdogs are quite small and tough to de solder using this method.


liquid flux + solder wick works well for me.

If you are drilling out holes make sure you dont drill out any vias, solder wick and a solder sucker usually does a sufficient job
but if you are only reducing the value of a resistor no need to remove it, just solder another resistor in parallel, or solder in a pot.

Thanks for the advice guys. I have a solder sucker, but I suspect the nozzle is too large.. And not very heat resistant. Time for an upgrade I think☺

I've not been very successful with the solder wick in the distant past. Time I tried it again.

Good point about the drilling. I was enlarging the holes very slightly.

Ray

[Koala]

If you are drilling out holes make sure you dont drill out any vias, solder wick and a solder sucker usually does a sufficient job
but if you are only reducing the value of a resistor no need to remove it, just solder another resistor in parallel, or solder in a pot.

I use to replace ICs on home computer everyday with a solder sucker. The holes on Silverdogs are quite small and tough to de solder using this method.


liquid flux + solder wick works well for me.

[6666]

Also spent ages redrilling the holes with a pin drill.

If you are drilling out holes make sure you dont drill out any vias, solder wick and a solder sucker usually does a sufficient job
but if you are only reducing the value of a resistor no need to remove it, just solder another resistor in parallel, or solder in a pot.

[raygdunn]

Here is a good example. Impulse has .55 volts on pin 1 of the 40106. This is an actual measured voltage, not a simulation. This clearly exceeds the absolute maximum input voltage rating of TI. This 40106 also is not working correctly. It introduces additional pulses that should not be there. They are runt pulses ( smaller than normal) the occur on the rising and falling edges of the transmit pulse. These may have no effect on the Baracuda operation, but they should not be there!

One simple solution would be to cut the trace that leads to the +5 volt regulator very near the 33k resistor attached to pin 1 of the 40106. Cut the trace between the 33k and the regulator NOT between the 33k and pin 1. This will allow R17,18, and 19 to float. Then tie this point to pin 14 of the 40106 with a thin jumper wire. This hold place pins 1 ,3 and 5 at 0 volts which is still a logic high and will not exceed the chip specs. However it will likely alter the timing of the two timing pulse and require resistor value adjustments.

if someone can look this over it advise if I have this right that would be great.

Well that looked a simple change, but I made a meal of it. My part replacement skills are useless. At least I've now made myself a nice hook tool from a bit of wire. Levering on adjacent components really wasn't a good idea. I probably should have done a YouTube search for methods. Also spent ages redrilling the holes with a pin drill. (Maybe the bit was not hard enough). Is there a good desoldering tool that clears the components holes?

For me the adjusted resistors are:
33K : 13.3K (two for the pulse widths). I used 10K+3K
150K : 56.6K (interpulse gap) I used 56K

So I now have:
First sample pulse: 44us (schema 45us. Original was 40us)
Pulse gap: 141us (target was 144ms to match my original)
Second sample pulse: 50us (schema 45us. Original was 40us)
<br>So I've badly matched the pulses. My conclusion is that though the sample width resistors were adjacent on the strip they must have varied. The original pulse widths I think matched fine.

Presumably zeroing NE5534 output is intended to balance this out. (It was actually only about 0.02V out)

Works fine anyway. Yet to try it in a less noisy environment.

Ray

[raygdunn]

Ray the 390 vS 330 ohms can make quite a difference. Not for troubleshooting but for optimizing. On my detector critically damping the finished coil, adjusting the offset and carefully adjusting the delay gives 30% more depth. This is more than all other changes I have made combined!
We will optimize that later once the coil is finalized, that is, if you wish.

Any more depth would be very nice. I had assumed it was more about faster decay times. I did this on the PI-1, but didn't test range before and after.

I saw 390 ohms as a useful change, as would need increasing anyway and I've seen no signs of oscillations on a pretty standard wind 10" coil. I furvently hope Qiaozhi can figure out that coil movement problem, so I can really up that resistor with a spider type coil. Way beyond me I think... Though I still have to try adding the extra components.

Ray

[ivconic]

Good points Ivconic but you ARE an English speaker! Indeed your English is better than many Americans.

Speaking of "speaking"....

P.S.
Thanks to Davor!

[Qiaozhi]

Very interested to hear what you find out. Do you plan on checking ours the incorrect pull up reference we have been discussing?

Yes - I intend to check everything.

[Old cart]

Indeed too bad! World would be a better place if it was based on enthusiasm like we are having it here.

"... the difficulties non English speakers ..."

Actually, the language itself is not a problem. It is easy to learn and understand. No need for translators. At least i don't use them at all in last dozen years.
What can be problem from time to time is not the language but the context and a way of thinking.
Different people, different minds, different way of thinking and expressing here.
And over the top there is also a "modern" way of talking; using too much abbreviations!
Internet introduced too many funny and crazy abbreviations lately. Sometimes it is problem to connect all those together in a thought which is making any sense!
And additional obstacle may be difference in education and different levels of knowledge here.
Highly educated and conversant people can easily understand each other with use of strictly "technical" language and common professional phrases and terms.
Lightly educated enthusiasts and hobbyists (my category) however will need a bit of more "human" explanations and help to understand some of the articles.
So it's not always about language, pretty often is about many other "side" factors.

Good points Ivconic but you ARE an English speaker! Indeed your English is better than many Americans.

[Old cart]

Well ... we will find out soon!
Impulse is sending me his Baracuda PCB (with coil and cable) for testing, so we'll get to the bottom of this in the near future.
Once testing is complete I will post a sticky with the official schematic, and ask Silverdog to put it on his website as well.

Very interested to hear what you find out. Do you plan on checking ours the incorrect pull up reference we have been discussing?