New Hammerhead Project

[KingJL]

Good eye

BW,
Yes, it is a typo. The resitor between pin 2 and ground is a 1K. Sets the gain at 10.

I will correct and repost!!!

Thanks!!

[KingJL]

Corrected schematic

Corrected schematic attached.

[bugwhiskers]

Hi KingJL,

Attached is a .PDF to setup the PWM.

regards
bugwhiskers

[rajesh]

hammerhead r 23 problem


I got the following voltage from IC7 CD 4016 bcn

Pin 1> –0.70Volt
Pin 2 >0.00 volt
Pin 3 >0.00Volt
Pin 4> 0.70 volt
Pin 5> -5.00 volt
Pin 9 >-2.70 volt
Pin 13 >-5.00 volt
Pin 14> 5.00 volt

TP2, TP3 is 0 volt if R5 open
Hi all I can't seem to zero out pins 2 and 3 of ic8. Everything up to this point has been ok. Any clues as to this. What should I look for. I think all my values are right. I'm following your directions but am clueless.. I can adjust r18 to zero out tp4 but nothing with r23.

I got the following voltage from IC6 TL o81.

Pin 1> 4.70Volt
Pin 2 >-0.04 volt
Pin 3 >0.00Volt
Pin 4>- 4.90 volt
Pin 5> -4.70 volt
Pin 6 > 0.00 volt
Pin 7> 5.00 volt
Pin 8>0.00 volt
I got the following voltage from IC9 pin 3 > -1.16 volt /
Pin 4 > 4.90 volt IC8
Pin 7 > -0.40Volt IC8
Pin 8 >5.00 volt IC8
I got the following voltage from test point
TP 1 >-0.60 Volt
TP 2 >-0.57 volt
TP 3 >0.04Volt
TP 4> 0.70 volt
TP 5> 0.00 volt
TP 6> -5.00 volt
TP 7> -5.00 volt
TP 9> -0.40 volt
I not used just coil all part ok with vco option
please tell me whats wrong .>>>>> rajesh

[KingJL]

I got the following voltage from IC7 CD 4016 bcn

Pin 1> –0.70Volt
Pin 2 >0.00 volt
Pin 3 >0.00Volt
Pin 4> 0.70 volt
Pin 5> -5.00 volt
Pin 9 >-2.70 volt
Pin 13 >-5.00 volt
Pin 14> 5.00 volt

TP2, TP3 is 0 volt if R5 open
Hi all I can't seem to zero out pins 2 and 3 of ic8. Everything up to this point has been ok. Any clues as to this. What should I look for. I think all my values are right. I'm following your directions but am clueless.. I can adjust r18 to zero out tp4 but nothing with r23.

I got the following voltage from IC6 TL o81.

Pin 1> 4.70Volt
Pin 2 >-0.04 volt
Pin 3 >0.00Volt
Pin 4>- 4.90 volt
Pin 5> -4.70 volt
Pin 6 > 0.00 volt
Pin 7> 5.00 volt
Pin 8>0.00 volt
I got the following voltage from IC9 pin 3 > -1.16 volt /
Pin 4 > 4.90 volt IC8
Pin 7 > -0.40Volt IC8
Pin 8 >5.00 volt IC8
I got the following voltage from test point
TP 1 >-0.60 Volt
TP 2 >-0.57 volt
TP 3 >0.04Volt
TP 4> 0.70 volt
TP 5> 0.00 volt
TP 6> -5.00 volt
TP 7> -5.00 volt
TP 9> -0.40 volt
I not used just coil all part ok with vco option
please tell me whats wrong .>>>>> rajesh

rajesh,
by looking at your voltages, I suspect that you have Q8 & Q9 installed. The adjustment routine listed in the article is accomplished with Q8, Q9, and IC8 NOT installed. With Q8 and Q9 NOT installed there should be something approaching +5V on pins 5 & 13 of IC7, that will allow the procedure to be completed as stated.

[rajesh]

h h

hi >> KingJL
actually im missing c26 but now working detector thanks for reply.i planing to change c 19 can you suggest me ? rajesh .....

[KingJL]

hi >> KingJL
actually im missing c26 but now working detector thanks for reply.i planing to change c 19 can you suggest me ? rajesh .....

No suggestions here, I used .47u per the original plans.

[gef12]

Corrected schematic attached.

Hi Kingjl
Just looking at your schematic
Any particular reason you chose an AD8031 over an AD8055 for the second opamp..
The AD8055 has a faster slew rate ..lower noise I thinks and wider bandwidth.. Just curious...
thanks
gef

[KingJL]

Hi Kingjl
Just looking at your schematic
Any particular reason you chose an AD8031 over an AD8055 for the second opamp..
The AD8055 has a faster slew rate ..lower noise I thinks and wider bandwidth.. Just curious...
thanks
gef

gef12,
No real reason. I had considered it, but selected the 8031 because I knew it had performed well as a single stage pre-amp. I really wanted to evaluate the split pre-amp properties, in particular the 797 running non-inverted as the first stage. The noise figure of the second stage is not as near as important; the S/N performance is pretty much dictated by the first stage. I have found that sometimes the specs can be misleading in that they may look great and end up for some obscure reason perform abysmally. I am not saying this is the case for the 8055, because I simply don't know. When I am trying to evaluate one change in a design I attempt to not introduce other unknowns. In this build I had already changed more tha I like to at one time (DD, split pre-amp, gain contol (reduction), and GB). But except for the gain control, the areas of impact were fairly well isolated.
I am still evaluating the results, but so far I am well satisfied with the outcome.
In my next project, I plan on using a AD600 VGA as the second (and probably 3rd) stage. The VGA will be uprocessor controlled of course.

If you decide to check out the 8055, let me know the results.
Regards,
J. L. King

[gef12]

Ye am currently testing / running first stage ad797 then ad8055. First stage gain of 150 inverted then gain 1 non-inverted 2nd amp. Should really try the other way around ... will be moving house soon so not getting much into it at the moment. Using lower gain infront end then making up for it in later stages. This seems to be working ok thou would like to improve it more. May even try ur approach with the ground channel that looks ok. Also this is a low power unit so helps a little with the ground problem me thinks.
cheers

[KingJL]

Ye am currently testing / running first stage ad797 then ad8055. First stage gain of 150 inverted then gain 1 non-inverted 2nd amp. Should really try the other way around ... will be moving house soon so not getting much into it at the moment. Using lower gain infront end then making up for it in later stages. This seems to be working ok thou would like to improve it more. May even try ur approach with the ground channel that looks ok. Also this is a low power unit so helps a little with the ground problem me thinks.
cheers

Just a note to remember: When you use the 797 at relatively low gains it is important to shunt the feedback R with some capacitance or you WILL have oscillations (this area is also addressed in the data sheet, though not in depth). In my case with a gain of 10 (which seems reasonable), I used 10pf shunt capacitance (the oscillations actually stoped with 1pf).

[KingJL]

Project Complete

Well, the project is complete. Now to exercise it!

Attached are scope pics of pre-amp output, Tx current pulse, Flyback signal. The IC3 drain and source pics only show the traing edge of the Tx coil waveform.

Scope settings:
preamp - 2 usec/div .5v/div
flyback - 2 usec/div 50v/div
IC3 source - 2 usec/div .5V/div
IC3 drain 2 usec/div 2V/div

Also attached are final pics of the completed MD.

It has been interesting, fun, and very rewarding!

Regards,
J. L. King

[bbsailor]

Well, the project is complete. Now to exercise it!

Attached are scope pics of pre-amp output, Tx current pulse, Flyback signal. The IC3 drain and source pics only show the traing edge of the Tx coil waveform.

Scope settings:
preamp - 2 usec/div .5v/div
flyback - 2 usec/div 50v/div
IC3 source - 2 usec/div .5V/div
IC3 drain 2 usec/div 2V/div

Also attached are final pics of the completed MD.

It has been interesting, fun, and very rewarding!

Regards,
J. L. King

J.L. King,

I have been following your progress. Nice Job!

What was the final value of the damping resistors on both the RX and TX coils and the inductance values for the RX and TX coils?

What distance do you get from a U.S. nickel in the air? Try this test outdoors away from noise for the best results.

One last question.

As a result of building and modifying the Hammerhead PI circuit, what is the most valuable thing that you learned?

bbsailor

[KingJL]

J.L. King,

I have been following your progress. Nice Job!

What was the final value of the damping resistors on both the RX and TX coils and the inductance values for the RX and TX coils?

Damping Tx 560 ohm, Rx 680 ohm.
Inductance Tx ~294uH Rx ~416 by your recommended calculator; my cheap LC multimeter indicated TX 260 Rx 360

What distance do you get from a U.S. nickel in the air? Try this test outdoors away from noise for the best results.

~22cm (in my 20V boost Tx mode about 30cm)

One last question.

As a result of building and modifying the Hammerhead PI circuit, what is the most valuable thing that you learned?

That I can still learn. (be shown new facets of things that I already knew or thought I knew). I have you to thank for that. I would not have achieved these results without your input.

bbsailor

I had sent you a PM concerning one of the scope photos. The answer does not have to be private. I did not know you were following my progress!
regards,
J. L. King

[rajesh]

hh new project

my dear friend king jl very good setting.whats coil dia meter actually my requirment 12inch dia ms plat up to five feet.can you do this detect in free air ?.......rajesh