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Offline lazzyTopic starter
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« on: January 26, 2011, 05:01:07 am »
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Dear Friends,

Has any of you come across the construction of EPE Magnetometry Logger?

If so, please reply, particularly if you have gone all the way and finished it to the point of proper functioning.

I have carefully constructed  and thoroughly tested the kit, but I cannot succeed to make it function properly: it seems that either the pic code or the board circuitry design is faulty.

Any advice would be much appreciated!

thanks in advance  Idea

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Offline GoldDigger1950
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« Reply #1 on: January 26, 2011, 02:29:35 pm »
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Describe the problem. What is it doing or not doing?

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« Reply #2 on: January 27, 2011, 03:07:16 am »
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Dear GD1950

I am glad to hear from someone out there!

Please allow me to describe the problem I'm experiencing:

Only the first time I ran the instrument after construction, it went through the whole cycle of functions described in the article (showing for example, the sensor's readings, the intensity bargraph, etc.) - but this only lasted for about 10-15 seconds and only in the first run; after that, I constantly get the following 'unstable' behaviour:

- lcd shows some info, then goes blank; sometimes, lcd remains blank from switching-on (but sampling beeper beeps and diode flashes)
- eeproms are not detected (although present) or detects only one of them (however, the unit may still work without any eeprom attached)
- after the initial 'welcome' messages, information on the lcd is intermittent: there appear some numbers, sometimes like the ones shown in the magazine article, sometimes unidentifiable rubish
- response to panel switches is also problematic: for example, diode D1 is activated with 'Record' switch and diode D2 with the sampling rate

This behaviour exists with/without the sensors attached, and even with replacing the pic with a pre-programmed one (I use Velleman K8087 for programming, while the pre-programmed pic is supplied by Magenta Electronics).

I have tested all connections, re-programmed the pic many times, but behaviour remains 'unstable'.

Persons who further tested the kit, advised that it is electronically ok and thus the problem should be with the pic program code. But how does this explain the "correct" behaviour in the first run?

Personally, I think the problem is somewhere else, perhaps in some faulty component or the circuit design... I have thought about the eeprom chips, but the unstable behaviour is still there without them; I have also replaced the crystal, no improvement; also thought about improper programming of the pic, and for that reason I tried to use a pre-programmed pic, but the problem still exists!

One last thought: could the problem appear due to the pcb tracks? for example, due to some damaged, but not visible, parts of the tracks, resulting in a haphazardly unstable power in the circuit?... Or is it definitely a pic-code problem?...

I would like to thank you in advance for any suggestions, hoping that I would finally not abandon the project at this very late stage (and all my efforts so far)...

Regards
Lazzy          Idea

p.s. I have seen some negative comments elsewhere, suggesting that the epe magnetometer project is problematic and not of any use; however, I have already constructed the epe reslogger -by the book- and it works just fine! I generally appreciate John Becker's work and dont think that any of his projects is unusable... 

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« Reply #3 on: January 27, 2011, 12:13:52 pm »
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I just located the July and August 2007 EPE and have printed out the articles. Let me look them over. In the mean time, here's something from the September issue with a circuit correction.

"In the Sept. 04 issue (P.623) we advised that the correct number for Speake & Co., the suppliers of the flux sensors, should be 01600 780150 and not as printed. In the Nov. 2004 issue we said that on Page 474 Fig 6, the FGM6 legends for Sig Out and GND have been transposed. GND is pin 2 and SIG OUT ispin 3. The wiring connections to the PCB should be transposed."


I really can't see that being the problem but it will impede proper operation later for certain.

Posted on: January 27, 2011, 07:46:35 PM
In looking it over, I suggest that you add a 30k resistor between pin 40 on the PIC chip and ground. You should be able to do that easily on TB1 using alligator clip leads to test it. Or just wrap it round the posts and crimp the leads to hold it in place. If it works, solder the resistor to the back of the PC board.

The PIC chip can become unstable in operation if the data in pin is left floating during operation. Normally, a 22k resistor in series with pin 40 and a 10k resistor to ground on the input side of the resistor is added for stability.

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« Reply #4 on: January 27, 2011, 01:18:26 pm »
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Dear GD,

Many thanks for your reply and suggestions so far, particularly with respect to the pic resistors.

Please do have a look at the project description (in the July 2004 article) and let me know of any other shortcomings you may discover.

I may mention here the fact that in the geotech website forum, a guy reports that he successfuly completed the project and it is working, the only concern being some deviation in the measured values of the two sensors, namely about 10-50 units (nT?) - but, apart from that, he claims that overally the kit behaves ok.

I, too, think that the project should be generally well designed and useable.

Regarding the corrections/comments about the sensors' connections, etc., which appeared in later issues (after July/August 2004), I would much appreciate if you could send me copies of the relevant articles, if possible.

regards, lazzy

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« Reply #5 on: January 27, 2011, 02:53:55 pm »
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Quote:Posted by lazzy
Regarding the corrections/comments about the sensors' connections, etc., which appeared in later issues (after July/August 2004), I would much appreciate if you could send me copies of the relevant articles, if possible.

That WAS the entire correction article. I quoted the entire thing. Nothing more was said. It would account for his sensor error, though. Perhaps you should go back to Geotech and tell him about the errata.

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« Reply #6 on: January 28, 2011, 12:27:55 am »
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Ok, I got it! And thanks once more.

Could I refer to your reply and relevant text about the errata on the Geotech forum, in case someone would like to contact you for further discussion?

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« Reply #7 on: January 28, 2011, 12:58:23 am »
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Certainly but I have no additional information. Just site the post I made with the quote in it. I have looked over the article and the schematic and other than the floating data pin, I see no errors. The newest revision of the PIC chips with that part number can't tolerate a floating data pin if you set it up for in situ programming like he did. That could very well be your problem.

Have you tried the resistor? If 30k doesn't work, try 22k. Then 10k. Let me know what you find.

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« Reply #8 on: February 25, 2011, 12:09:09 pm »
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Do you have an update on the status of this project?

Crane

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« Reply #9 on: February 25, 2011, 03:25:14 pm »
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I was hoping to hear from the project builder myself. Either my suggestion worked and he's off using it in the field somewhere or he's given up.

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