Barracuda.....update(2)

[1843]

Hi Geo,

Simply add the high pass filter and two diodes after the HH preamp... Also change the HH integrator TC... It becomes a Barracuda!

Regards!

[Altra]

Problem with Hex Trigger

Leto,

The schematic has a mistake Pin 14 "VDD" goes to ground or battery minus.
The CD40106 operates between the -5v rail and Vref (B-). The rest of the drawing looks OK.

Mark

[Geo]

Hi.
The schematic is very closed to Whites Surfmaster.
Whites use a 4066 for sample switch (from +v to -v) and a 4093(from +V..(+5V) to (-V)...-5V) to generate the samples. In general words very closed schematics.
When i will try it i"ll see on the scope.
Regards

[Altra]

Fets

Hi Geo,

FET demodulators work better when switched between Vref and V-. Where as the cmos demodulators (4066) need rail to rail switching.

[kt315]

here is original schematic. are you still remember of it?.... NO?! then we will go to you!!

[Altra]

schematic

Hi Kit,

Your schematic is full of mistakes. The connections all look good except R19 goes to V+ not V-. Someone has mixed all the resistor and capacitor values around so that it will never work. As an example look at the feedback resistor on the NE5534, 22k with the 1M to ground? The 1m should be the feedback resistor with a 1K to ground. This schematic will work like an LRL.

[porkluvr]

wrong R31 value?

Hello Leto-

The value shown for R31 at the input to U1E (240kΩ) makes no sense.

Consider this: (k)R31*C11 and (k)R6*C10 set the sample pulse widths, and both channels should probably have equal sample times. Considering the same "C" values, if the bottom channel uses 1KΩ, why wouldn't the top channel also use 1kΩ? Well, unless some funky magic going on. Besides, U1E won't trigger with that value of R31, the way the circuit is drawn.

In my LTspice simulations, sample widths that I see when using 1kΩ for R31 and R6 are not are not -exactly- the same, but pretty close (with about 2% variation). The top channel pulse (going to the FET on the non-inverting input of U4A) leads the bottom channel by about 18us.

[Geo]

Hi KT... It has wrong values, do you have the original?????
For example U3 writes 555 but must be ICL7660. Also there is difference at 5534 at offset balance.

[porkluvr]

duh, did you do that.

I fully believe that anybody who would draw a schematic diagram that calls an ICL7660 by the name of ua555 needs some education. mmm

[kt315]

Hi KT... It has wrong values, do you have the original?????
For example U3 writes 555 but must be ICL7660. Also there is difference at 5534 at offset balance.

Geo, why you do not find ALL info on the subj in the archive??
be more newsy and read anywhere you see BARRACUDA here! >>>>>>>
https://www.geotech1.com/thuntings/a...x.php/f-8.html

NOTHING OF NEW ON SCHEMATIC YOU WROTE ABOUT

[porkluvr]

wada wada need some wada

The Barracuda circuit (as shown in Barracuda pre2) seems to have an extremely long delay between time of transmit pulse and time of sample.

Delay time is adjustable - but is usually more than 1 ms! ouch.

1ms delay might be good for scuba dive metal detecting (I can only guess, with my being a land lubber and all), but it would be relatively insensitive to most land based objects smaller than an automobile!

I have played with simulation to try and to shorten delay time, but this circuit does not want to accomodate me. Mebe it's my fault. I dunno.

I think CD4538 circuits (ala HH, GS) are more readily adjustable.

[Geo]

I made a new pcb (Ap. send it to me ) and i will try to make it.
1ms is very very long time for first delay, so i will try to change it.
Now i must find the ICL7660.
When i will finish it i will write here
Bye

[kt315]

the original schematic clearly indicates that R6 connect on V-, Rtot on GND, R8 on V-. could try to correct and simulate again.

[Geo]

Thanks KT...
It is time to check the pcb. Now my Barracuda is ready, when i will take the ICL7660 (i have order it) i will try it. It is a classic schematic so i am sure that i will find the errors and to make it to work perfect ( because as i wrote Barracuda was one of the best PI detectors).
Regards

......porkluvr can you simulate again the circuit with editing the errors who KT315 sent here???

Regards

[Alexismex]

Hello Forum
In the past I experiment with barracuda schematic (full of errors) but the result was good after many hours of search
Here my version of Barracuda Timing gate , 100% functional (I use in many detectors) , very good and stable, simple because you get the control of two timing with ONE IC: 41106,
if you want you can change the sample wide window (6K ,the PPS ,the pulse wide,delay, very easy...
Have a good time...