Whites Surf PI schematic

[nelson]

How Cordius.
What kind of cable did you use btw coil and circuit.
In my case i used ordinary electric cable with good results. But last weekend i use rg-58 coaxial cable, and results wehe to bad.
By the way this is my third surfmaster i have done with good results.
Kind regards
Nelson

Good work Kuraja
This is my final version of surfmaster.
There is only one pot tresh
the disc pot is setting onbord trimmer R25 50K and bridge 100K pot for full performance.
Coil is 20 cm diameter.

[lari]

How Cordius.
What kind of cable did you use btw coil and circuit.
In my case i used ordinary electric cable with good results. But last weekend i use rg-58 coaxial cable, and results wehe to bad.
By the way this is my third surfmaster i have done with good results.
Kind regards
Nelson

what are the results from the surf-master detector?
depth?

[cordius]

How Cordius.
What kind of cable did you use btw coil and circuit.
In my case i used ordinary electric cable with good results. But last weekend i use rg-58 coaxial cable, and results wehe to bad.
By the way this is my third surfmaster i have done with good results.
Kind regards
Nelson

Hallo Nelson, I use RG 58 and normal cable, there are not difference of results in my home experiment in the old version of the circuit that you know.
Next days i finish mounting the new pcb, today i have mounting the resistors and same capacitors, there are same mistrake in the new pcb. Add two pad for J7 bridge and J4 bridge.

[nelson]

Hi, in my case for a 22 mm copper coin on air, 26 cms.
Regards
Nelson

what are the results from the surf-master detector?
depth?

[nelson]

Hi Cordius.
Well i wil have to check thecoax i used, cause it didnt made any good results.
When you use btw normal cable and rg58, did you made any re-adjustments to the circuit, specially to the dumping resistor?
Regards
Nelson

Hallo Nelson, I use RG 58 and normal cable, there are not difference of results in my home experiment in the old version of the circuit that you know.
Next days i finish mounting the new pcb, today i have mounting the resistors and same capacitors, there are same mistrake in the new pcb. Add two pad for J7 bridge and J4 bridge.

[Waikiki_Sweep]

I have assembled detector by using oxygeno07 layout. It works!!!
Not so good as I was expected, but works. 26 cm for 1 euro coin in air. (Not a loud and clear but makes a signals). 22 cm loud and clear.

1. First, I have found and fixed mistake with placement Q6 (BC337) in oxygeno07 layout.

2. I have used twisted pair to connect coil. !!! IT WAS WRONG !!! Once I have wires untwisted sensitivity has doubled.

I think capacitance of twisted pair or RG58 coaxial cable may interfere. I expect better results with RG6 coaxial or even flat electric power cabele (not twisted).

3. I have replaced C9 1000pF with 470pF. Look like more convenient for range of pot P3.

I have tested two coils: 24 cm, 21 turn, 0.41 mm and 25 cm, 19 turn, 0.6 mm. Both make similar results.

Second coil with 0.6 mm wire makes little increace in power consuming 5 -10 mA. And may be 1 cm in sensitivity. Both coils are flat (spiral).

My device consuming 50 mA electric current from the batteries. WHAT IS YOUR RESULTS FOR CURRENT?

I have checked that 25 mA is for schematic and 25 mA used by coil because all consumption remains only 25 mA when 555 generator is off. (no impulses to the coil)

SOME EXPERIMENTS

I have tried to double enegry that sending to the coil by rising duty cycle from 10 uS to approx 20 uS by increacing R2 from 3.3K to 6K (just add 2.7K in line) As result sensitivity increases to 3-5 cm. (low level signals I can hear over 30 cm.) But consumed power has been rised to 75-85 mA.

Also here is reserve to increase frequency by reducing R2. It may increase sensitivity but it will rise power consumption too.
You can see on osciloscope some signals from carrent schematics:
1 - impulse to the coil (collector Q1), 2 - main probe (pin 4 U4), 3 - sample probe (pin 3 U4)

_1_2_____3_________________________1_2_____3______ __________________

You can see that here is enough space to double frequency from 600 to 1200 Hz.

_1_2_____3________1_2_____3________1_2_____3______ __1_2_____3________

If you need osciloscope here is FREE software that turns your computer into advanced osciloscope: http://www.sillanumsoft.org/download.htm

You can connect audio LINE-IN of your computer to your schemes but PLEASE put 100 K resistor and diodes to protect computer input from
high voltage. (Same as diodes D1 and D2 on detector schematics protecting input of NE5534P)

Also I have added bright LED between P4 and Q6. It may help to use detector without headphones in water or at night. It flashing pretty well for even small targets.

I am using headphones. If you will use speaker then better install LED from +12v to colector Q6 with 1 K resistor because 50 mA current through speaker may burn the LED.

[Waikiki_Sweep]

Can somebody help to find a company where we can just layout file and receive PCB?

It was a real pain to assemble detector on Grid-Style PC Board from Radioshack http://www.radioshack.com/product/in...ductId=2102843 because I am unable to find any parts or technology here in Honolulu.

Can somebody help to find a company where we can just send layout file and receive ready PCB by mail for reasonable price?

Also I can recommend http://www.taydaelectronics.com to buy a parts. Most of them. For example IRF9640 is only $0.50 here. They will send you parts from Thailand for very low privce. Shipping is low price too. It will cost $1-2 to send by USPS mail. Delivery approx. 1 week - 10 days. (To USA. For other countries please check.)

But please check resistors you will receive from Tayda because sometimes they make errors. I have received 240k resistors in plastic bag marked "15k". So I had 2 days headache to find why my detector is not working.

Some parts that I am unable to find on Tayda I have purchased on http://www.digikey.com It is more expensive. You can see the same IRF9640 for $2.39 Delivery time is same or little smaller: 5-7 days and shipping affordable too. USPS First Class approx $2. (For USA)

[Alexismex]

Hello Waikiki,
goto
http://www.expresspcb.com/index.htm
draw your board , after the software will give you the price , send your files via the same software , and two days or three your will have yours boards very professional boards.I have work with them ,very cool service and super fast...

[Geo]

Hello Waikiki,
goto
http://www.expresspcb.com/index.htm
draw your board , after the software will give you the price , send your files via the same software , and two days or three your will have yours boards very professional boards.I have work with them ,very cool service and super fast...

Hi Alexis.
I use this program, but i never sent any file to construct me a pcb.
What about the prices for pcb and the minimum quantity of constructed pcbs???

Regards

[WM6]

"Our board manufacturing service makes top quality two and four layer PCBs.

Use our MiniBoard service and pay only $51 for three boards (plus shipping)."

[cordius]

fantastic!!!
50 euro cent at 30 cm!!!!!

[geminis74]

Cordius congratulations, has remained stable, with no noise of mass? the coil is 350UH and 3.3 Ohms?, thanks.

[cordius]

Md is very stable in house, no noise or other problem.
Coil is 23 cm and 20 turns 3,3 ohm. I do not know inductance.

[bklein]

Hi guys,
I plan on making this detector due to its simplicity etc. but ....
I recently acquired a Surfmaster PI - the real deal, with 9.5" coil.
I would like to maximize its sensitivity and really do not see anywhere the trim procedure. Can someone do a writeup of the trim procedure? I have a scope etc. and would like a description of test points and what to look for... What should the open air sensitivity be on a US cent or dime? Don't have any EU coins handy....
Also I see some of you say you are doing simulations of this circuit. Could you post your LTspice simulation file?
I'd also like to see some discussion on the use of LTspice for your circuit optimization. I am just learning the program and its quirks. Curious how the simulation has a realistic receive signal to work with. How is your simulation written so to represent faint receive signals of various metal types? I realize this is a lot of things to ask for but what I read mostly here is - "I can't get mine to work like yours....." and this kind of information would go a long way to resolve such issues.
Thanks, Barry

[porkluvr]

Hi guys,

Also I see some of you say you are doing simulations of this circuit. Could you post your LTspice simulation file?
I'd also like to see some discussion on the use of LTspice for your circuit optimization.
Thanks, Barry

I have using LTspice to analyse some detectors but the Surfmaster circuit defies me.

LTspice does not come with CD4000 family device models so someone wrote their own and passed them around. Those models are what I've been using. For the most part the models work for normal logic circuits, but for some reason CD4093 schmitt trigger NAND device models (and also CD40106 schmitt inverters as used in the Anchor Barracuda) do not trigger correctly when used as one-shots.

Without being able to simulate the sample timers there is no way I can help with the Surf PI. PSpice or CircuitWorks might be able to handle the circuit but that is beyond me. Or, maybe somebody could describe how to correct the commonly used LTspice schmitt models.

For the received signal, what I have done with CD4538 based PI detectors is to kludge some arbitrary RLC network and maybe a diode to rectify the ringing, between the transmit and receive coils to delay the fall time at the receiver preamp.

That is not an accurate representation of any particular target but can be useful to provide -some- input to the preamp and integrators. Unfortunately, that's not much use here without having the sample timers running.

I would like to resolve the issue one way or another but time is limited and for me it is just not a priority.