MPP Beach REV-E

[Goaty]

Hi all,,,,If I make this Damping tool to set the Damping resistor of my MMP Rev D and E, can I use ordinary 1% or 5% 1/4 watt resistors with an ordinary 10k Potentiometer? Thanks in advance. Marty

Just in case anyone builds this and can't get it to go down to 118R as specified, I think that figure is a typo and should be 181R minimum.

[Qiaozhi]

Just in case anyone builds this and can't get it to go down to 118R as specified, I think that figure is a typo and should be 181R minimum.

http://www.geotech1.com/forums/showt...785#post227785
http://www.geotech1.com/forums/showt...ool#post226164

[Goaty]

http://www.geotech1.com/forums/showt...785#post227785
http://www.geotech1.com/forums/showt...ool#post226164

Yep - your links correctly show min 181R but the image in post #69 of this thread says min 118R. Could cause some confusion.

[Phantom]

George,

Have we in any place the full revision E schematic in only one sheet as we have for revision D?

It is useful for me to see all the circuit in one look.

Thank you.

Regards

[Qiaozhi]

George,

Have we in any place the full revision E schematic in only one sheet as we have for revision D?

It is useful for me to see all the circuit in one look.

Thank you.

Regards

I have added the schematic as requested -> MPP Beach REV-E

[Phantom]

Thank you very much sir

Best regards

[samsearcher]

Just started making the Revision E board. All OK up to step 5, but not seeing much action from the very basic 'test' coil (25 turns around 190mm dia former, 0.22mm enamelled wire, not screened ). Does anyone have 'scope photos from the various test points so that I have some idea what I should be seeing?

THANKS

[Qiaozhi]

Just started making the Revision E board. All OK up to step 5, but not seeing much action from the very basic 'test' coil (25 turns around 190mm dia former, 0.22mm enamelled wire, not screened ). Does anyone have 'scope photos from the various test points so that I have some idea what I should be seeing?

THANKS

Have a look at Fig.7 - Coil Configurations.
Do you have pin 2 of PL1 connected to pin 2 of PL2?

[samsearcher]

Yes Rx and Tx pins linked, coil between link and ground. TP3 Scope pulse changes when a can is near, but not amplitude?
or is this OK for a very 'crude' coil?

[Qiaozhi]

Yes Rx and Tx pins linked, coil between link and ground. TP3 Scope pulse changes when a can is near, but not amplitude?
or is this OK for a very 'crude' coil?

[ATTACH]45475[/ATTACH][ATTACH]45476[/ATTACH][ATTACH]45477[/ATTACH]

That looks fine to me. If the pulse moves along to the right when metal is near the coil, then it's working correctly.
The preamp output shows the last part of the decay curve as it approaches 0V. Initially the preamp is saturated due to the huge input signal. But, as the signal exponentially decays away, it comes out of saturation. When metal is near the coil, the decay takes longer, and hence the curve moves to the right.

[samsearcher]

That's great, thanks for the info, I'll press on then!

john

[waltr]

That looks fine to me. If the pulse moves along to the right when metal is near the coil, then it's working correctly.
The preamp output shows the last part of the decay curve as it approaches 0V. Initially the preamp is saturated due to the huge input signal. But, as the signal exponentially decays away, it comes out of saturation. When metal is near the coil, the decay takes longer, and hence the curve moves to the right.

Yep, the scope traces look perfect.
Remember that the first sampling will be just as the decay curve approaches zero without a target. With a target the Voltage during the first sample is much lower thus producing a change on the output of the integrator stage.

[samsearcher]

Well that's all finished, seems to detect well (even with that basic coil) are there any links to case/handle/stems anywhere?

[waltr]

Great news on success on this project.

Lots of posts on DIY cases, poles, etc.
Many go to their local hardware store and look at the PVC pipes and fittings.

[samsearcher]

I'm just getting back to the MPP-Beach after final coil potting, and going over the preset adjustments.

I read about the benefits of a 'fast coil'....in Step 6, Adjusting the sample delay on TP6, instructions state 10uS, I can adjust for a minimum of 5uS before it cuts out.... is this a measure of how fast the coil is? and better for detecting than 10uS?