SurfMaster Pro III (My Version)

[Sean_Goddard]

I have attached a modified version of the Surfmaster for you all to play with.

Watch the DC voltage on that big fat 250V cap, it WILL bite you and give you a nasty jolt if you don't take care.

Just the machine to try my superfast coil on!

ENJOY.

[Virdi_248]

You have already built surf pi III?

[Sean_Goddard]

This is a new design, based on the Surfmaster Pro PI from Whites. I have looked at where the circuit needed some modification to improve performance like no -ve DC generator, and low value resistors to reduce gaussian noise. I have also stepped away from the silly practice of high gain front ends which have too high a Tau level and thus saturate. Gain should be made up at the DC and LF stages. The idea is to throw this out to people to play with. My design has been simulated and breadboarded and gives good depth and sensitivity.

Still the subject of a multilayer PCB as a work in progress, so no not built ans a machine. works as a prototype no reason why it shouldn't work as a machine once built in a case.

[WM6]

I like so many controls you provided, Sean, - ideal testing and learning platform.

I wish you offer pro-multilayer PCB of this design or even kit's.

[6666]

Thanks Sean.

[Jose]

Hello Seand Goddard
Thanks for sharing this project.
I'm looking at the schematic, and I can see that the pulse width of the first and second sample, alrrededor 50 microseconds, judging by the values of R119, 121 and C115, 121.
I wonder if there is no error, given the high rate of 4 kHz.
Regards and thanks again.
Jose

[Sean_Goddard]

Hi Jose, Yes, you could well be right about those values. I have copied them from another project I was working on at the same time, they may well be wrong. Please experiment or advise what values should be used.

I'm laying out the PCB as we speak, 2 layer so far but I might go for more to get the supply planes right.

All capacitors are Wima 2.5mm pitch polyester caps. They have excellent characteristics and they look great too. If you use metal oxide resistors throughout (1%)

I will post Gerbers and DIPTRACE files when available.

Schematic; https://dl.dropboxusercontent.com/u/...ond%20Case.dip

DIPTRACE; http://diptrace.com/download-diptrace/

I intend to make a "mezzanine" board to mount the pots and controls on for speed of assembly.

[Jose]

Thanks Sean Goddard
Unfortunately, I can not see files DipTrace yet, I have installed a previous version free, and some work done on it. I'm afraid of losing some work.
Be installing the new version, with help from people with more knowledge than me.
I'm anxious to see the design of the PCB.
Best Regards
Jose

[Sean_Goddard]

Hope to have that PCB finished within a week or so. Getting ready for a new job so that is taking up my time at the moment.

[CAS]

Hi Sean

Was just looking at your schematic - D101 in the TX circuit - its across the coil. Is it supposed to be on the other side of D102? When I look at the circuit all that goes through my mind is that there would only be .6v across the coil.

[Sean_Goddard]

Hi CAS. Silly me, D101 is NOT supposed to be there at all. Sorry about that. I have no idea why I put that in there. I havve an updated schematic, but as I'm on board a ship at the moment I cant post it as it's a large file and we get billed by the MB. I will post the new one when I get home.

Also I spotted that the Tx frequency is way out so I went back to 2KHz. That works just fine so the values need to be changed there. If you change the main 555 cap in a standard SM PI to 15nF from 22nF the Tx runs at 888Hz instead of the old 600Hz, it makes the machine MUCH smoother. Also, if you add the snubber to the SM PI it also makes it better.

I built Silverdogs kit and I get around 340mm in air on a 18ct Gold ring using a 300mm search coil wound using 16AWG magnet wire. Nothing special but it gives a great smooth threshold and great sensitivity to small objects. So many improvements to the SM PI I was trying to put them all in one design but I used an old design of mine and reworked it. Looks like I missed a few things that should have been taken out. I need to go back and look at this schematic again when I have the time.

Thanks for your input, very helpful.

[Schall]

Good day Sean_Goddard.
Tried the input layout part. With 555 3pin 50us on gate Q102 22us came. Q104 was open, close began after installing a resistor with a base on the ground. Couldn't understand why D102 C106 R102.

[daverave]

Hi sean
could you give me a schematic for a simple snubber circuit for a surf pi.

many thanks
David

[bernte_one]

Hello Sean,

are you back from the boat? I hope you are allright?

Are you still working on this Project?

[eclipse]

I think it's better to replace the components driving the voltage to the mosfet with discrete Mosfet driver IC