Delta Pulse

[porkluvr]

thanks friend
my pcb is on page: http://www.geotech1.com/forums/showt...a-Pulse/page82
if you want video for the true delta i can upload.
my delta work but is poor
thats sens a box 12*5cm in 7cm in air
i think my coil isnt good,i change some part for better sens gold and small object
friend please help me..

What is the value of the damping resistor you are using? I can't see it in the picture you showed me. The damping resistor is the one that connects directly across the coil.

[alonejax]

What is the value of the damping resistor you are using? I can't see it in the picture you showed me. The damping resistor is the one that connects directly across the coil.

are your end of damping resistor that resistor other side irf840 fet?
this is 680 ohm 2wat
bro do you now how i can understand my lf357 is real lf357 and it's not tl065 or els & work normaly?
tahnk you

[porkluvr]

are your end of damping resistor that resistor other side irf840 fet?
this is 680 ohm 2wat
bro do you now how i can understand my lf357 is real lf357 and it's not tl065 or els & work normaly?
tahnk you

One problem you have is that your damping resistor is probably too high for the coil you are using. I can't really tell you what is best (not with any certainty) because that depends on your coil, cable, FET... and some other things. From what you told me earlier I calculate your coil inductance at about 460uH, with only 1.9Ω series resistance. You previously stated the resistance being higher, but did you subtract the multimeters lead resistance??

All I can do from here is plug in an IRFP460 spice model into quick DP transmitter simulation in LTspice, make an "educated" guess at your coil parameters, and then try out different damping resistors. I look at settling times, and the value of damping resistor that settles the fastest is "the winner". That might seem dumb, but I don't have any better way of working.

What I have determined is that something like 430Ω or maybe 390Ω (2W) would probably be a better choice for your damping.

I can only guess at the coil and cable capacitance of your rig, so, my analysis is not very scientific. It is a lot of guesswork. But, my unscientific (virtual) analysis seems to indicate that with 680 ohms, your coil's fly-back would take more than 50us to settle, which bothers me. With the correct damper you may be able to knock 20us off that time.

By the way... the big honking "1.5k" resistor in your picture looks to me more like 1.0kΩ, (brown black red gold (?!), and that, being the preamp input resistor affects my "winner". I will assume you are using 1.0kΩ unless you tell me different. But that resistor's effect is not nearly so great as your coil/cable combination, and like I said, that is a big guess from where I sit.

Damping resistors are something that have to be determined through trial and error, so having multiple values to play with is a good thing. You can try paralleling 1/2 watt resistors across the damper until you can determine the "correct" damper value, but that is not meant to be permanent. A 1/2 W resistor will not withstand 500V pulses for very long...

You should be aware that at the higher settings of your "noise" (pulse-width) potentiometer, (with a low resistance coil) you will be shooting a good deal of current through your FET. A heatsink is a very good idea.

And do not use the highest PPS setting at the highest PW setting, or else you can expect the FET to run very warm.

Did the person who sold you the kit give instructions for making a coil for you to use with it?
I used to think that bigger is better when it comes to coil wire, but that ain't necessarily true.
**********************************************

I have no idea how to tell if your LF357 is the genuine article.

[zlatica]

Hi all, I have a problem with my DP, works, depth is not bad, but DP is not stable. Coil is 42 cm diameter, 29 turns with 0,5mm wire. Damping resistor is 2,2K 1W. Does anyone know what the problem is? Sorry, my english is bad.

[kt315]

Hi all, I have a problem with my DP, works, depth is not bad, but DP is not stable. Coil is 42 cm diameter, 29 turns with 0,5mm wire. Damping resistor is 2,2K 1W. Does anyone know what the problem is? Sorry, my english is bad.

find out my post about anti E-field shielding inside housing. that is strong and hard necessity for DP as DP is working in static mode and is very sensitive device.

[zlatica]

Thanks

[jap]

are your end of damping resistor that resistor other side irf840 fet?

Hi alonejax
-U entered into a problem using another number
U use irfp460,,,If U returned to the original number may get rid of the problem,
-The original is IRF740 or 840------>Must be tested by the first.
best time
j.

[alonejax]

hi jap
thanks bro
i change that for test,
jap, can you help me to build nice gold detector please ?

[ouiarabe]

HI maximusdesmus
change the lcd 1X16 by 2X16

[alonejax]

hello again kt315
i'm sorry if i bugging you for privet massage
i only want you help me, excuse me !
i want to build a good gold detector for dept
if you help me i so thanks
Good luck!

[alonejax]

very very very thanks porkluvr
i get many your time....
i wish happy time for you and i can make up for your oblige
i think in your guide and come back again my friend

[maximusdesmus]

HI maximusdesmus
change the lcd 1X16 by 2X16

Hmm,the lcd is 2X16, the flat cable goes only to the one pinned side.
Why did you suggest me that?

[ouiarabe]

Hmm,the lcd is 2X16, the flat cable goes only to the one pinned side.
Why did you suggest me that?

excuse me my friend I did not pay attention your circuit discrimination with PIC16F676

[RS_Phil]

Hi! Nicolas did you solved the problem of your LCD discrimination? what programmer you,re using? I have the same problem,.

[Orbit]

hekskod wrong !!!!!!!!!!!!!can not be resolved Turkish business !