Delta Pulse

[Tepco]

U4 is input amp, U6B acts like integrator, (R19/C16 time constant) auto-zeroing U4 when U9D is closed. U4 (LF 357) is somewhat specific chip, whit common mode range accepting +V, and about 100mV above (can not be replaced whit 5534 or some other typical PI opamp), circuit will work this way. Power supply distribution on XR71 in complete nightmare, but works, no matter how strange it looks, figure out what is GND reference for what part of ckt.

[sevar12]

hello every one
now i see that ne5534 not be the same as lm 357 may be this is a problem to dp not work

[Tepco]

No way to work whit 5534 (or anything similar)

[sevar12]

Yes i see thenk you very much

[mehdi]

Hi friends
anyone know how i can increase strobe impulse to 1000 us in delta pulse?

best regard

[Jose]

Hello Mehdi
Change C1 to (22 nf) by 1.5 nf
Change R1 to (470k) by 68k.
Set PR1
Be careful with power.
regards
Jose

[mehdi]

Hello Mehdi
Change C1 to (22 nf) by 1.5 nf
Change R1 to (470k) by 68k.
Set PR1
Be careful with power.
regards
Jose

Hi jose, vary thanks
please answer to my second question;
haw i can decrease pps to 25 Hz or low?
what mosfet is more powerful than irf740 that i can use in delta pulse?(except irf840)

thanks in advance

[Jose]

Hi mehdi
25 hz for the DP is very low.
If you want to experiment, increase the value of C1, adding capacitors in parallel to achieve the desired frequency.
The forum could see "Mos" higher power, can not remember where.
Mos higher power generally used in low coils are inductance and low resistance ohmic.
It is not the case of DP, where the opposite is true, inductors and high resistance.
I have no experience other than the IRF840 transistors.
By adjusting power properly, you get good sensitivity, cold remains the "Mos" and low battery consumption.
regards
Jose

[Tepco]

Hi friends
anyone know how i can increase strobe impulse to 1000 us in delta pulse?

best regard

This is about last thing you need (25HZ and 1000 uS pulse?!?). Do exactly opposite, increase frequency, and keep reasonable pulse duration (min. to half "power" setting), and you will see improvement.
Btw, from what is your coil made of? Cryogenically cooled superconductor or what? Or just plane old wire. Calculate ohmic losses and compare to current that should be reached whit 1mS pulse for given inductance, and you will see this is not exactly good idea, except if you want to waste power to heat the coil.

[kt315]

Eric Foster gloss

The metal detector is one of the primary workhorses of the treasure hunter, particularly of the hobbyist THer. There are three primary types of detectors. Frequency shift designs include beat frequency oscillator (BFO), phase-locked loop (PLL), and off-resonance. Induction balance (IB) encompasses transmit-receive (TR) and very low frequency (VLF) detectors, as well as two-box detectors that are sometimes referred to as RF (radio-frequency). Finally, there are pulse induction (PI) designs.

PULSE WIDTH. The width of each individual transmitter pulse. Depending on the detector and its intended application, the pulse width can vary between 50 microseconds (uS) and 1000uS. 50 to 150uS is usually the width for ring and coin size objects while wider pulses suit detectors designed for locating larger objects. A boat towed PI designed to look for cannons would likely use 1000uS. Examples are:- Whites Surfmaster 50uS, Deepstar 100uS, Aquapulse 300uS, Superscan and Aquapulse towed 1000uS.

PULSE FREQUENCY or PULSE REPETITION RATE. The number of times the transmitter pulse is repeated every second. The frequency affects the response speed, power consumption and interference rejection, although all of these are influenced by many other factors in the circuit design. Examples are:- Surfmaster 800 pulses per second (p.p.s.) Deepstar 3000 p.p.s. Aquapulse 170 p.p.s. Superscan 66 p.p.s.

[mehdi]

very thanks for your great helps.
all the best
mehdi

[sevar12]

Finaly i finde LF357DP but DP not work good.I try with diferent coils(18 cm) from 730uH to 2.1mH (6om to 9,6om) and dumping 680om to 2.2kom but for plate 10X15 cm maximum range is 6cm .Somwhere i have mistake but no scope and be difikult to find but i try.I use bord one side .Byt with small dumping (680 om ) is more stabilish.

sorry fore bad english

[Tepco]

Build proper coil.

[sevar12]

find mistake on 556 pin 10 no +Ucc in my pcb an fix it .Now work good and stability.Soon make a nwe coil about 40cm diameter or 40X40 now with 30cm 0,8om 430uH detect 1 euro fom 16-18 cm.I try to put a swich for frequency for small and big coil .

[Tepco]

This is much better now, 6-9.6Ohm, 730uH to 2.1mH for 18cm coil is way off. 30cm, 0.8R, 430uH is right one, should do better whit 1E, maybe interference.