Delta Pulse

[kt315]

hi all

it is ok to use irfp460 or no?

thank you

try it. it is better on data vs IRF740 but needed in experience.

[pigeon]

hi all

it is ok to use irfp460 or no?

thank you

[Dean Sarelius]

Hi All,
I have tried replacing the op amps especially DA2(LF357) and DA4(TL062) but without any success. I have also tried swapping out DA3 and DA5 but this made no difference either.
Here are some pics of my gold its not much but it is still more than the M4 screw which I am testing..!

[calebsone]

any progress with the mod dean and if so what steps did you take?

[kt315]

I am trying to make it detect gold but without any success...???

hello Dean, thank you lots for pics of your job. it's perfect!

can you give pics of this gold sample you use? what weight, size, is of it? yes, normal famous fact that a PI detector is more sensitive
to ferrous than to gold. nothing new I do not see here, Eric, Carl, wrote about this fact many times.
also. have you did learn Eric's Foster diagram coil size vs target size more sure?

[Dean Sarelius]

Hi Jose,
Thank you for your comments this is very re-assuring..!
First I think I will look at replacing the LF357 with a faster slew rate op amp and see what difference this makes..!
If changing the op amp doesn't work then I will look at the TX pulse width..!

[Jose]

Hi Dean
I want to discuss my personal experience with the DP if it's any help, this may be wrong, but this is my finding on the issue.
Small gold is difficult to detect with the DP.
You can change the delay to work on minimum values, but the response of the amp (LF357) can reach 17 or 18 microsecond minimum value by design, and this limits the ability to detect small gold, besides the SAT, it is a bit slow.
However, you can spot a good gold ring in 30 or more cm.
Another thing you could see is that it is not stable with low resistance coils. The total resistance including cable, should be 2.5 ohms, or greater.
Also the frequency and pulse width TX, affects performance.
For small objects, works well up to 400 or 500 Hz.
The TX pulse should be between 100 and 200 microseconds
greetings

[Dean Sarelius]

Hi Kt315,
The coild I am using is a flat spiral wound coil is 10inches long and about 8 inches wide refer to the attached picture.
When I measure the inductance with an inductance meter is measures about 300uH.
I have includes some pics of the assembly also..!

[kt315]

Dean, what size diameter your coil is?

[Dean Sarelius]

Hi Everyone,
I lowered R5 to 470 ohm and lowered C5 to 1nF still DP3 will not detect gold.
I can place a tiny M4 screw almost 10cm from the coil and it picks it up very nicely but when I place the same amount of gold right on the surface of the coil I get nothing..?
Question I have is has anyone been able to detect pure gold with the DP3 and if so what was the configuration..?

[calebsone]

yes please let me know i want to mod mine but not till after the season i want to use it for a bit first

[Dean Sarelius]

Hi KT315 and Calebsone,
Thank you for your help, I will make the mods which you have recommended and feedback the results to you within the next few days.
Cheers
Dean

[kt315]

Dean, this will effect T5 also because R8 C5 is general part for both timers. decrease C5 to 1nF. R5 also decrease to a value like guys write in surf pi and hammerhead pi topics(frequently asked questions). you need to tune R5 more precissionly in your case. for 40 and more usec FIRST DELAY not so need, but for 10-15usec yes.

[Dean Sarelius]

Hi Cabelsone,
Thank you for your help.
If I reduce C5 I gather this will effect T4 or will this affect T5 also..?

[calebsone]

dean i think R5 must be decreased not increased and C5 has to be lowered.