Surf PI Pro

[stefan646]

I am slowly putting the board together using the latest PCB made by ahcene2035 with NE555 instead of ICL7660 (the LT1054 is quite expensive :-" ).
The only thing I don't understand is how I trim the R2 pot (the one that sets the time of TCL555). After what frequency I am looking after? Or I must trim it based on the best detection range?

[bernte_one]

also take a bigger cap (4700-6800 microF) and set "pulse on" - pulse width time for longer time than 120microS

https://www.geotech1.com/forums/showthread.php?18655-Surf-PI-Pro&p=198193#post198193

[stefan646]

Yes it will heat more, but with a bigger radiator it should work fine. I will try it to see if I notice any difference in range

[bernte_one]

compare rDS(on)

[stefan646]

Hello,
Quick question: why not use IRF9610 instead of IRF9640 as it has less output capacitance?

[waltr]

You must have been using it incorrectly. One common source of error is to enter the diameter of the coil instead of the inner radius.

Another I found is the wire thickness. This seems to be the output diameter if the wire with insulation. This determines how close together the 'bundled' wires can be.

And anther is inside radius. If using a series of nails in a board then then ID can be different than the circle drawn.

[Qiaozhi]

You must have been using it incorrectly. One common source of error is to enter the diameter of the coil instead of the inner radius.

[dbanner]

Like I said, maybe I wasn't using it correctly, but when I tried using it for calculating coils in the few hundred microhenries, I found it to be less accurate compared to measured values.
Maybe someone else can check it out. Wind a coil of say 350uH using calculator, then measure the actual inductance.
The one I posted above is the most accurate I have come across for winding coils for pi( few hundred uH)
I never said it was restricted to values below 1 mH, I implied it was LESS accurate for values below 1mH.

[Qiaozhi]

For inductances below 1mH? Maybe I wasn't using it correctly.
Found something very accurate for hundreds of microhenries which I did actual measurements.

The Coil Calculator is not restricted to values below 1mH.

Most coil calculators are based on the Wheeler equation, which can handle the simple case of a single layer solenoid coil. However, metal detector coils are usually multi-layer, and the Wheeler equation can give incorrect results. The Coil Calculator is based on Brook's equation, which is able to aproximate the inductance of any air core coil. The Coil Calculator is intended for circular coils only, but the values can be fudged to also handle D-shaped and elliptical coils. Please see Appendix A of "Inside the METAL DETECTOR" for the complete details of how it works.

[dbanner]

i use this one, very good

[dbanner]

Dr op pped my negative rail on my surf down to -7.5V, picked up 3 inches. I don't care why. Im happy with it now.

[dbanner]

At the top of the COIL forum is a calculator. It works very well.

For inductances below 1mH? Maybe I wasn't using it correctly.
Found something very accurate for hundreds of microhenries which I did actual measurements.

[Carlos]

hello, please, you can put the new circuit in PDF? Thanks
Carlos

[solmer2]

Thanks!!!!

[Tibuck19]

Hi folks! My Surfmasters works pretty well but I want to make a new coil (9"). How many turns of 22awg or other awg gauge should i use for a 9" coil?

Thanks in advance for your help.

Convert your inches to MM , Use the coil cal to find the number of turns http://www.geotech1.com/forums/showt...oil-Calculator
You can use a chart like this, to find the size of your wire in mm https://www.tedpella.com/company_htm...uge-vs-dia.htm
You might also want to read the pdf on how to make a fast coil, A 22awg coil will not detect small things like gold rings very well.

FastCoil.pdf