Hammerhead made But problem with detection

[Nikil]

Hi Carl,

I just made my hammerhead with through whole PCB. If I use IC6 is NE5534 it is very much noisey and detection is almost not working, but if I use IC6 is LM318 It is working but detection is very low depth. It can detect a 4-inch nail cutter at 10CM with very high pitch sound. If R5 is open IC6 PIN6 voltage is + 4.2 and no effect with R18 at this time (Q8 and Q9 is not installed) and TP4 is always 4.2 volt. If R5 is close and If I move R18 the voltage is vary at +2.19 to + 3.8 volt but I never found at TP4 0volt. I don’t found any effect R23. But across PIN 2 and 3 of IC8 is always 0 with PAD1 of IC7 is grounding. I use R11 at 680 ohm. I use IC NE555, 74HC221, LM318, TL072, 40066BE and transistor Q3 is IRF740, 2N3904, 2N3906.

Carl Please help me

Nikil

[Carl-NC]

"If R5 is open IC6 PIN6 voltage is + 4.2 and no effect with R18 at this time"

Well, we need to figure this out, because it's the problem. Double/triple check supply voltages, namely IC6 pins 7 & 4. Also check the voltage across C27, you should be able to vary it (via R1 from -1.7v to +1.7v. Check that IC6-pin3 is 0v, and TP2 is 0v.

- Carl

[Unregistered]

Hi,
I got the following voltage from IC6

Pin 1 + 2.33Volt
Pin 2 0 volt
Pin 3 0Volt
Pin 4 - 4.88 volt
Pin 5 2.37 volt
Pin 6 3.32 volt
Pin 7 4.74 volt
Pin 8 -3.76 volt

TP2, TP3 is 0 volt if R5 open

It is working but detection depth is not satisfactory as others mention. I chnge R 17 to different valuse but TP4 never get 0 volt.

At R5 connected I found following voltage

TP1 -0.5 volt
TP2 -0.09 Volt
TP3 -0.06 volt
TP4 3.32 volt
TP5 -3.9 volt
TP6 5.50 volt
TP7 -5.03 volt
TP9 -1.15volt +0.5 volt


My VCO work quite well, when detect any metal it sound with Hi pitch.

My coil is 11 inch .

The detector detecting depth is only 3 to 4 inch for a 4 inch nail cutter and i found it is noisy inside house but out side it is stable.

[Carl-NC]

"Also check the voltage across C27, you should be able to vary it (via R1 from -1.7v to +1.7v."

[Unregistered]

Thanks for your reply. Yes I cheek the voltage across C27 and I found a small soldering problem here, after solve this problem its voltage is vary from -2.12 volt to +2.12 volt. But still IC6 pin 6 voltage is vary from + 2.7 to +3.12 . Detector is working but not satisfactory level.