Powerful PI or Hammer Head (how to increase power of coil?)

[rajesh]

hh

rajesh

15 turns is about right for this coil with a 53.5" perimeter. This is equal to a 17" round coil.

See my article for more coil making details.

http://www.geotech1.com/cgi-bin/page...oils/index.dat

bbsailor

hi bbsailor while i using 15 turns. i found very low sensitivity can you recmonde me to modifie r3 r4 ......rajesh

but same time i use 4" coil that working fine.

[nick_f]

Hi Rajesh,
From what I understand, BBsailor provided you with details for building a larger coil with about the same recommended inductance (around 320uH). If you say it has lower sensitivity than the smaller coil, you are right. I've been explained that by having fewer turns in the coil, the sensitivity as a receiver is reduced. A large diameter coil will be less sensitive to smaller targets, but it should detect the large targets at a larger distance than a smaller coil.
To increase the sensitivity of large coils, Tinkerer has a suggestion, to use a concentric coil. The smaller coil would be the receiver coil and for the same inductance, it will have more turns than the outer (transmitter) coil. I can't remember if there is necessary to have another coil, to cancel the field of transmitter coil in the receiver coil. I think it is not necessary for Pulse Induction circuits (like Hammerhead).

Regards,
Nicolae

[rajesh]

hh

Hi Rajesh,
From what I understand, BBsailor provided you with details for building a larger coil with about the same recommended inductance (around 320uH). If you say it has lower sensitivity than the smaller coil, you are right. I've been explained that by having fewer turns in the coil, the sensitivity as a receiver is reduced. A large diameter coil will be less sensitive to smaller targets, but it should detect the large targets at a larger distance than a smaller coil.
To increase the sensitivity of large coils, Tinkerer has a suggestion, to use a concentric coil. The smaller coil would be the receiver coil and for the same inductance, it will have more turns than the outer (transmitter) coil. I can't remember if there is necessary to have another coil, to cancel the field of transmitter coil in the receiver coil. I think it is not necessary for Pulse Induction circuits (like Hammerhead).

Regards,
Nicolae

hi nick i'm using mono coil. i need to 1oo hz frequency and 256 us man pulse width as like gary has done his pulses induction metal detector.....rajesh

[nick_f]

I made some tima ago a program for calculating the values of resistors and caps for 555 working as an astable circuit. I can't guarantee it works ok, but I remember I was getting good results with it last time I tried it.
I took a screenshot of it and I also attached in here, if anybody wants to give it a try. Basically it sais that: R1+R2 = 136.9kOhm, R3+R4 = 3.7kOhm, C8=100nF.
That means you can have R1 = 56k, R2 = 100k, R3 = 10k, R4 = 1.5k and you have to change C8 to 100nF instead of 10nF.
You can give it a try, but I am not responsible if your MOSFET blows up
If you have a frequency counter, or some headphones, you could listen to the sound produced at pin 3, if it resembles 100Hz.
Maybe somebody else can confirm the results I obtained.

Regards,
Nicolae

[rajesh]

hh

I made some tima ago a program for calculating the values of resistors and caps for 555 working as an astable circuit. I can't guarantee it works ok, but I remember I was getting good results with it last time I tried it.
I took a screenshot of it and I also attached in here, if anybody wants to give it a try. Basically it sais that: R1+R2 = 136.9kOhm, R3+R4 = 3.7kOhm, C8=100nF.
That means you can have R1 = 56k, R2 = 100k, R3 = 10k, R4 = 1.5k and you have to change C8 to 100nF instead of 10nF.
You can give it a try, but I am not responsible if your MOSFET blows up
If you have a frequency counter, or some headphones, you could listen to the sound produced at pin 3, if it resembles 100Hz.
Maybe somebody else can confirm the results I obtained.

Regards,
Nicolae

hi nick you mean .1mfd =c8 i have a 555 astable multibibrator callculator. www. telus.com/ i shall be tring this setting

[nick_f]

Hi Rajesh,
I said 100nF (100 nanoFarad), which is 0.1uF (0.1 microFarad).

You said 0.1mF (0.1 milliFarad), which is 100uF (100 microFarad). It is a big difference and you have to be careful with the units, otherwise your circuits won't work.

Regards,
Nicolae

[nick_f]

Hi Rajesh,

You mentioned there is an astable calculator on www.telus.com. Could you please provide a link? I searched on Gary's web site and I couldn't find it.
Meantime I found another one, at http://www.csgnetwork.com/ne555timer2calc.html Capacitance has to be entered in Farad, and Resistance in Ohm.
To introduce in that calculator 100nF, you have to enter 100e-9
For 136.9kOhm, you have to enter 136.9e3
For 3.7kOhm, you have to enter 3.7e3
With these details, you will see that the values I provided will help you generate 100Hz and 256us pulse width.


Regards,
Nicolae

[rajesh]

hh

Hi Rajesh,

You mentioned there is an astable calculator on www.telus.com. Could you please provide a link? I searched on Gary's web site and I couldn't find it.
Meantime I found another one, at http://www.csgnetwork.com/ne555timer2calc.html Capacitance has to be entered in Farad, and Resistance in Ohm.
To introduce in that calculator 100nF, you have to enter 100e-9
For 136.9kOhm, you have to enter 136.9e3
For 3.7kOhm, you have to enter 3.7e3
With these details, you will see that the values I provided will help you generate 100Hz and 256us pulse width.


Regards,
Nicolae

hi thank's nick this is good calculator. 100 hz is ok but i need some high pulse width for that coil....rajesh

[nick_f]

Hi Rajesh,

Just tell me what is the width of the pulse you want and I will give you the R and C values. What can be simpler than that?
Last time you asked for 256 microseconds, I provided you the values required for resistors and capacitors.
If you want 100Hz and 500 microseconds pulse width, just use: RA=129kOhm, RB=7.22kOhm, C=100nF.
And I consider the program I attached for you is better than the calculator on that web page.

Regards,
Nicolae

[rajesh]

hh

Hi Rajesh,

Just tell me what is the width of the pulse you want and I will give you the R and C values. What can be simpler than that?
Last time you asked for 256 microseconds, I provided you the values required for resistors and capacitors.
If you want 100Hz and 500 microseconds pulse width, just use: RA=129kOhm, RB=7.22kOhm, C=100nF.
And I consider the program I attached for you is better than the calculator on that web page.

Regards,
Nicolae

hi nick i used frequency and pulse width like as gary done hi pi. carl-nc wrote his article cmose verssion for ic 5. what is the diff. between cmose version or TTL NE555

[nick_f]

Hi Rajesh,
If Carl recommended the CMOS version of 555, then you should use that one.
I used standard 555 and the circuit works well. I didn't have to add a pull-up resistor (to ground) on pin 3.
I don't know what is the difference in practice for this circuit between CMOS 555 and standard 555.
They have higher impedance, lower currents, lower power consumption, lower spikes and they are faster. And probably more precise.

Regards,
Nicolae

[rajesh]

hh

Hi Rajesh,
If Carl recommended the CMOS version of 555, then you should use that one.
I used standard 555 and the circuit works well. I didn't have to add a pull-up resistor (to ground) on pin 3.
I don't know what is the difference in practice for this circuit between CMOS 555 and standard 555.
They have higher impedance, lower currents, lower power consumption, lower spikes and they are faster. And probably more precise.

Regards,
Nicolae

hi nick actually i have use NE555 TTL that. so i need to knowe which vallue will be fit of pull up resister ic5 pin 3 to ground. can you tell me how to recognige a cmos/ttl. there are some calculator.
http://www3.telus.net/chemelec/Calcu...alculators.htm

[nick_f]

CMOS Astable 555

hi nick actually i have use NE555 TTL that. so i need to knowe which vallue will be fit of pull up resister ic5 pin 3 to ground. can you tell me how to recognige a cmos/ttl. there are some calculator.
http://www3.telus.net/chemelec/Calcu...alculators.htm

Hi Rajesh,
NE555 are not CMOS. For example, LMC555 and TLC555 are CMOS.
You can notice there is a C after LM or TL, indicating the IC's are CMOS.
Also, LM7555 is CMOS.
There might be some others, but I don't know them. You can use google and search for "CMOS 555".

Regards,
Nicolae

[rajesh]

hh

Hi Rajesh,
NE555 are not CMOS. For example, LMC555 and TLC555 are CMOS.
You can notice there is a C after LM or TL, indicating the IC's are CMOS.
Also, LM7555 is CMOS.
There might be some others, but I don't know them. You can use google and search for "CMOS 555".

Regards,
Nicolae

hi thank's nick actually my hemmarhead giving me some noise but i don't understand where is wrong i'm curently using ne555 of ic5 tp no.7 is very fluctuate and audio continues doing sound. you can see my built hh image above......

[nick_f]

Rajesh, do you have an oscilloscope? How do you know TP7 fluctuates? TP7 should be identical with TP6, just a bit later in time. That pin should give very clean pulses and it is a simple circuit, almost identical with the circuit that provides signal at TP6. Compare the signals or voltage levels at pins of IC11 with IC12, they should be identical.
Also, the voltages of Q8 and Q9 should be the same.

Regards,
Nicolae