RELIC HAWK

[porkluvr]

Robopatt,
Your desire is admirable, but you are spinning your wheels by encountering trouble and trying to fix it by replacing parts instead of examining the situation.

Beg, borrow, or steal, but get an oscilloscope. You should try to isolate the problem instead of shotgunning everything. There are so very many little things that could be causing problems.

It is absurd that anybody would think to make IB metal detector from scratch, untested schematic, and make it work without having oscilloscope and a good deal of experience.

Robo, puhleeze get a scope and give everybody a break.

Robopatt why don't you list previous pages of this topic? Instead bugging and harrasing here?? None of your handmade will ever work, considering very none of your knowledge and understanding. Looking at your trivial question i am sure it will be better for you to buy new metal detector, instead trying to make one.
Are you tiktak, ultimate haze or not - does'nt matter. Tiktak, ultimate haze and you acting exactly the same; hundreds of trivial questions, zero understanding and zero knowledge.
With posts like yours this forum turned to very low level. Those few experts already left this forum, mostly cose of anoying persons like yourself. People can not appear here and deal with real things in fear that you and simillar to you will attack with bedlam of stupid questions and demands! Empty and trivial questions and stupid remarks. Sorry, life is rude.

[robopatt]

Now I see.
Can you Please post the wirings for that previous PCB,so I can try it.

[Max]

how many ????

Hi,
Max.
I am very glad that you are finaly here.
Have you checked this last schematic?Why there are 3 X 393?In yours there is only one 393?
Now I have some "idea" about that TR.Could it be this?

Hi,
I see.... it's Ivconic's reduced schematic I think....

Now back to the problem: 3 x lm393 or 1x lm393 ??? or both ?
Or... well... Ivconic's reduced schematic has 4x lm393.... really. (u3, u7, u11, u12)

You must consider also that there's an LM339 in original RH (we know that) and an LM339 contains 4xcomparators (an LM393 just 2) so it's like say that 4xlm393 are like 2xlm393 + 1xlm339.... do you understand what I mean ?

Kind regards,
Max

[Max]

Yes, the circuit is ugly but that does not mean that it will not work.
Now I've got it. My test setup was faulty and I was acting like a dog chasing his tail.

One bad thing about spice is that it is hard to simulate circuits that generate ground because spice likes for ground to be the starting point, not an end. And, if it's ground then it's always going to be zero volts. (duh) You can't measure it, it's just THERE. Believe it. It's true.

Here I have hopefully corrected my error. It would take a lengthy explanation or else a picture. I'll draw a picture because I don't feel smart enough to make a lengthy explanation.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%

Here I have called battery(-) "ground" and ground is "0V". LTspice will not allow me to draw the circuit as it is would be in real-life, but I must transpose. In my picture we can see that if you have a 10V battery, the "0V" will be almost exactly half-way between B+ and B-. V+ and V- would get out of symmetry when the battery voltage is NOT 10V, so I don't understand why Minelab would do this. But, if it works, who cares?

Whew, I hate these crazy power supplies, but so what? Max, I thought your drawing was wrong but it was me that was wrong. Sorry.

Hi,
no problems... also cause drawing is not mine... I mean.... I added some value here and there but author is someone else.... that made reverse engineering on a real RH board.

All that voltages could be confusing... I know. The strategy itself is not bad at all... I see it good having a floating gnd with simm reference voltages for the trimpots etc. Looks really what I expect from that ML schematic... and the reference diode is another interesting thing: they wanna thermal stability from start, though not perfect stability thing seems well more advanced than having some old 7805 plus some voltage divider....I saw in other stuff.

And yes.... LTspice is useful but sometimes frustrating much....

Kind regards,
Max

[robopatt]

Ok.
So mistake is not mine.
I see in front of my eyes exacly what you describe.Start oscillate when you switch DISC/ALLM switch.
Bun now I have manage to fix coils in such position that I have good performance in DISC.Sound at the begining of detection is good.But on closer targets or fast swing only constant sound.

[porkluvr]

I appologize for not taking time to read. I would always get mad when somebody asks questions that have already been answered in a thread,
and here I am doing the same thing.

Yes, the oscillator startup can be a problem if everything is not "just right" and I haven't figured out exactly what is "just right". Not yet (although I might not EVER). I must give my 5kc RH oscillator virtual circuit a little "kick" or else it won't start. A little injection of coil current does the trick.

Just on a hunch I just now fired up my 20kc oscillator after removing the "initial conditions" (.ic ...) statement that I had been using. It did nothing for about 4ms and then took only 2ms to reach full output. It's like comparing apples and oranges, but maybe a clue as to what is happening.

If I Remove .ic from the 5kc oscillator it just sits there and does nothing. Forever. (Well, maybe not forever, but you get the picture.)

I think that the low-Q tank is a likely source of slow start-up, but then you also must have hi GBW transistor at Q2 and probably a low loss tank capacitor (polypropylene!!).

Increasing my 20kc coil resistance from 2.5 to 5.5 caused startup time to increase fom 6ms to 22ms, but it did start.

I lowered the 5kc oscillator coil resistance from 3.5 to 1.5, and it still does not seem to want to start without .ic.

Back to the salt mine.

edit: Oh yeah, using a gel-cell battery would definately make the floating ground to be a good cheap, effective power supply solution. What, it ranges from about 12.6V to 10V and then it's dead? (just a ballpark guess, not reasearched)

[robopatt]

Hi,
Porkluvr.
RH use 12V seled lead-acid battery.Max have excplained all.Just read.This diode that we tweeked at TX stage have to be 3V3.All there excpained.
Now when I switched on this PCB refuce to work like when I worked early.
Need time and then start oscilate.
I will recheck all.
Can you fins similar TR like this that I showed.Can this be the mistery SMD TX?

[porkluvr]

Could somebody tell me, does Relic Hawk use a rechargable battery pack, or 8 AA alkaline batteries, or what? Reason I'm asking is because I'm wondering about the range of supply voltage change from new battery to dead battery.

Thank you

[porkluvr]

Hello porkluvr,
For this circuit , it is not a temperature compensated for the Zener diode???just a idea ,because i do not know for sure !!!!

I just re-read your question and put into context with Max's last post.
Yes, the voltage reference should be LM336-2.5.

Every time I post a virtual circuit there is a likelyhood that I have taken shortcuts that, although my changes may be OK, probably would need some extensive testing in real-life before you or anybody would want to rely if you were three-hundred miles from civilization and a soldering iron!

[porkluvr]

... For this circuit , it is not a temperature compensated for the Zener diode???

If I understand you correctly you have noticed that I have substituted LM385-2.5 for LM336-2.5? That is purely a convenience for me. I do have LM336-2.5 model (thanks to Aziz) but I have not modified it to conform to the "standard" of other parts in my collection. Out of habit (and laziness) whenever I need a 2.5V reference I use the LM385.

LM385 and LM336 do have substantial differences, but for the purpose of supplying 2.5V in a simulation, I am not real picky. Sorry if I have caused (even MORE) confusion.

I think the LM336 in the RH circuit has much better guaranteed temperature stability than LM385. LM385 will operate over a wider range of current than LM336. Those are the main differences.

I have to make substitutions all the time because sometimes the "correct" parts just don't seem to want to get along with each other. (Notice the OP15C that I used; it's more "friendly" than the TL07x. They are not internally the same, but "sort of" close in performance.)

If that is not what you were asking please try and rephrase your question and I'll try again to answer.
*******************
(Referring to Max's original drawing): Here I would like to explain that when I had question before about the U10B circuit I was being stupid because I was operating U10 with +/-5V supplies. Well... If we had nice +/-5V supplies, then we wouldn't need U10B then, would we??
And, so long as the + and - supplies don't change too quickly, they don't really need to be symmetrical.

(It is more complicated and expensive but I am in love with the idea of using a low power switching power supply and having +/- 5V to operate the machinery. But that's probably just because I'm old, and my brain inflexible.)

edit: I'll edit my LM336 symbol in a day or two. I think the symbol/model works, but I need to make it easier to invoke.

Hello porkluvr,
For this circuit , it is not a temperature compensated for the Zener diode???just a idea ,because i do not know for sure !!!!

[porkluvr]

ground reference

Yes, the circuit is ugly but that does not mean that it will not work.
Now I've got it. My test setup was faulty and I was acting like a dog chasing his tail.

One bad thing about spice is that it is hard to simulate circuits that generate ground because spice likes for ground to be the starting point, not an end. And, if it's ground then it's always going to be zero volts. (duh) You can't measure it, it's just THERE. Believe it. It's true.

Here I have hopefully corrected my error. It would take a lengthy explanation or else a picture. I'll draw a picture because I don't feel smart enough to make a lengthy explanation.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%%%%%%%

Here I have called battery(-) "ground" and ground is "0V". LTspice will not allow me to draw the circuit as it is would be in real-life, but I must transpose. In my picture we can see that if you have a 10V battery, the "0V" will be almost exactly half-way between B+ and B-. V+ and V- would get out of symmetry when the battery voltage is NOT 10V, so I don't understand why Minelab would do this. But, if it works, who cares?

Whew, I hate these crazy power supplies, but so what? Max, I thought your drawing was wrong but it was me that was wrong. Sorry.

[robopatt]

Schematic post #748
Sprintlayout post #754