Delta Pulse

[demone]

this problem occur with many people


i can tell you the following


1-D9 AND D8 check if they good and not shorted

2- check the E- without connecting IRF740

it should be -10.6 with respect to E+

if you dont have oscilloscope as me

you can use buzzer to here some click sound at LM556 output

3- never start the machine with high power tx pot p3


4- low turns may make this problem

you need (2-4 ohms coil with 25 turns for small one and 16 or less for large one)


if all above was ok

connect the IRF740 or better replace it

dont connect the coil and remove R6 temporary

check with buzzer at the IRF740 GATE
is there any sound




*- very important note


c30 and c31 connected always to the battery then connected to the machine by switch
use c7 200 uf as this will speed up the generation of E-



REGARDS

Hi ossamaussama and thank you for the fast respond.
1-D8 and D9 both of them have a voltage between 0-0,03.They do not seem to conduct.
I disconected the IRF740 and checked the voltage bt it was -11.3 and not -10.6.
The has alrady worked on another delta pulse and it was just fine.

[ossamaussama]

Hi everyone.Recently i managed to "construct" the delta pulse.
My circuit works great.All the 4538's 062 etc working BUT i got 12 volt output there where i want to put my coil.I get 12V dc voltage.When i connect my coil(3.5R) i get a high current.As a result my Irf740 getting hot and i have to pull off the dc power!If i leave the coil for 4-5 sec my 740 is no more usefull;has been destroyed.
Enyone that could help?
Thank you!

this problem occur with many people


i can tell you the following


1-D9 AND D8 check if they good and not shorted

2- check the E- without connecting IRF740

it should be -10.6 with respect to E+

if you dont have oscilloscope as me

you can use buzzer to here some click sound at LM556 output

3- never start the machine with high power tx pot p3


4- low turns may make this problem

you need (2-4 ohms coil with 25 turns for small one and 16 or less for large one)


if all above was ok

connect the IRF740 or better replace it

dont connect the coil and remove R6 temporary

check with buzzer at the IRF740 GATE
is there any sound




*- very important note


c30 and c31 connected always to the battery then connected to the machine by switch
use c7 200 uf as this will speed up the generation of E-



REGARDS

[demone]

12 volt output in coil

Hi everyone.Recently i managed to "construct" the delta pulse.
My circuit works great.All the 4538's 062 etc working BUT i got 12 volt output there where i want to put my coil.I get 12V dc voltage.When i connect my coil(3.5R) i get a high current.As a result my Irf740 getting hot and i have to pull off the dc power!If i leave the coil for 4-5 sec my 740 is no more usefull;has been destroyed.
Enyone that could help?
Thank you!

[Jose]

"Remove or open collector T2 leg 5 of 4538"

Why?

Hello szucs_g
This circuit, T2, 4538, acts by increasing the delay time to avoid overload, with large objects near the coil.
For the detection of small objects with coils of 28 cm, you can override this, for a smooth adjustment of the delay control.
Regards

[ossamaussama]

to remove the effect of feed back network on delay


this work with small coil 28 cm

not with large coil that will not work good with low delay

[szucs_g]

"Remove or open collector T2 leg 5 of 4538"

Why?

[Jose]

This is my mod DP, to detect small objects.
To decrease the delay, change the value of "C4 =1 nf".
Remove or open collector T2 leg 5 of 4538
To reduce the gain, increasing the value of R6 1.5 K
Increasing the frequency to 600 Hz
Pulse width adjust TX 125 usec.
regards
Jose

[ossamaussama]

try this

to make delta pulse work with lower delay

need to reduce the effect of feedback network on delay sample

by inserting 50k

and the gain have to be reduced

so use pot 100 k instead of 20 k

to ensure stability

and use 300 hz instead of

100 hz


try it and its work

now it can detect small gold

http://www.geotech1.com/forums/attachment.php?attachmentid=17556&stc=1&d=1322337584

[szucs_g]

OK. Maybe my LM357 was wrong...

[Jose]

Not "You were wrong." The salesman were wrong. Sorry.

Hello Szucs
For your information, DP works best with the LF357.
regards
Jose

[szucs_g]

Not "You were wrong." The salesman were wrong. Sorry.

[szucs_g]

The mistake is found. I trusted the salesman. Said it, that it LM357 like the 356 good. You were wrong. Unfortunately this component it was not accused by me till now. The Internet department store's components arrived, I put them into it, but the 356 I exchanged it as last one only. See a miracle. It's working. It is possible to experiment with the depth. A battery of mine was destroyed in an alley. R.I.P.
Thank you for your help!
Newer moral! Only your own eye believe!

[porkluvr]

HCF4538 is not one to use. Datasheet states that minimum timing capacitance is 5nF which is higher than the 1.5nF used on the DP. This is stated on page 2 of the datasheet.

CD4538 and HCF4538 are not equivalent. They perform the same function, but HCF4538 imposes constraints on timing components where CD4538 does not.

(Don't know for sure but this restriction on timing components may be due to HCF4538 having schmitt trigger inputs where CD4538 does not.)

[szucs_g]

CD4538 these are in the PD.

http://pdf1.alldatasheet.com/datasheet-pdf/view/22373/STMICROELECTRONICS/HCF4538BEY.html

Theoretically -0,5 -18 volts it's working. The detector not yet indicates any metal.

[DOOLEY]

cheers porkluver ,

that explains why i had to nearly double the cx values to get the same timing pulses after i substituted a 4538 for a 4098 when i built a version of the blind squirrel.

they still works well ,but i found a site comparing the 4098 to the 4538 and it said "the 4098 is not as precise as the 4538"
i expected the worst with unstable / fluctuating timming , but no , all stable , happy with the 4098 , and there 1/2 the price.