Delta Pulse

[calebsone]

ok on that schem you sent paku they are vd8 vd9 and they are in section A 3 lower right corner good luck.

[paku]

omg you just give me the hint ok i will try but if not working i willl Exploit This Forum All DB will be gone Hahaha just kidding

[calebsone]

Is there any reason why two more 1N4001 could not be used, same as VD7? Those can handle up to 1 amp. They're slow, but so what?

the only problem could be the amount of voltage it takes for the 1n4001 to allow a voltage to pass i think the 1n4148 takes .07 volts so if the 4001 is the same the maybe it would

[kt315]

excellent job Salebsone! thank you for the video.
yes, 1N4001, 4002, 4004, 4006, 4007, will work only good because having more max current than 1N4148. also take 0,7V voltage drop like 1N4148.

[Dean Sarelius]

Hi KT315,
I have finished building the DP3 and I am very happy with the overall performance it is very good..!
I am trying to make it detect gold but without any success...???
I have a very fast coil it is decaying within 6-8us so have decreased R7 from 15K to 2K2 and increased the snubber resistor R5 to 820 Ohm but still no signal..?
Q1 - Should I increase R5 some more in order to make it more sensitive to gold..?
Q2 - Are there any other mods you can recommend..?

[calebsone]

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

[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..?

[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 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

[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 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..?

[kt315]

Dean, what size diameter your coil is?

[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..!

[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 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..!