Whites Surf PI schematic

[porkluvr]

I' don't know where is the problem on surfmaster??? it is very very simple to built!!!

Is it easy to adjust? I have problem with Surfmaster because I can't get LTspice simulation of the sample timing one-shots (built around 4093 nand gates) to run correctly. I'm not saying there is anything wrong, but it is impossible for me to analyze or confirm proper operation of the timing.

I do not believe that the timing circuits are particularly flexible, but that is only my opinion. If the RC components are not kept within a certain range, then the 4093s may fail to trigger.

I do not want to badmouth Surfmaster. It has a very low parts count for what it does. An alternative might be CD4538 circuits (or HC221 etc.), but when you use CD4538 one-shots; you may get more flexibility and straght-forward setup, but the parts count goes way up.

Surfmaster is certainly functional. It does what it does, but until I can flog it I could not possibly feel safe modifying downstream from the LM555 timer in the Surfmaster circuit. That does not mean that YOU should not do it, but I won't. That's just me.

This morning I have pulled out my instruction book and a copy of PSpice Schematics (which I once loved but now thoroughly despise). I will attempt to setup and play with the Surfmaster timing circuits. It will take some time... let me get going. MAYBE I can get Surfmaster working on my computer.

[cordius]

I' don't know where is the problem on surfmaster??? it is very very simple to built!!!

[nelson]

Hi porkluvr. Yes i think you are right, cause i have checked everyting and is fine.So now i´ll try to play with the damping resistor.
I ´ll post my results.
Thanks and take care.
Nelson

Hello Nelson,

I have a feeling that you should play around with the damping resistor. If you used 390 ohms; that is tailored to the IRF9640. I don't know if it should be larger or smaller but you should not assume that 390 is good for IRF9630. GOOD thing you have a scope!

I think the best value would be higher but I might have it backwards. I don't have a good spice model for IRF9630 to put into my stupid simulator.

update: I found a model and I'll compare IRF9630 and IRF9640 side-by-side. I think best: LOWER damping R (I changed my mind) but I want to run some tests.

[kuraja]

ApBerg...

Could you please make one layer PCB?

[porkluvr]

I used a test coil of 230uH, 1.4ohms, 234pf (234 is just a wild guess). Data gleaned from Carl's "Coil Parameters" page, for the Surfmaster Pro. Surfmaster is not listed.

http://www.geotech1.com/cgi-bin/pages/common/index.pl?page=metdet&file=info/coils/index.dat

(If anybody knows any difference in coil parameters for the Surfmaster, please share.)

If you must use IRF9630 I think you might better off with a damping resistor in the neighborhood of 430Ω.

Today I think I've learned that different damping resistors affect the decay curve differently depending on the value of coil and cable capacitance. Since this capacitance is an unknown quantity, I am blowing smoke if I try to pin down a "best" damping R value.

Whoops, I've stuck my neck out enough here to last for several days.

[porkluvr]

damping resistor?

One change i made is that i replace IRF9640 with IRF9630. Thank´s
Nelson

Hello Nelson,

I have a feeling that you should play around with the damping resistor. If you used 390 ohms; that is tailored to the IRF9640. I don't know if it should be larger or smaller but you should not assume that 390 is good for IRF9630. GOOD thing you have a scope!

I think the best value would be higher but I might have it backwards. I don't have a good spice model for IRF9630 to put into my stupid simulator.

update: I found a model and I'll compare IRF9630 and IRF9640 side-by-side. I think best: LOWER damping R (I changed my mind) but I want to run some tests.

[ivconic]

Hi Ivconic.
What cable did you se btw the coil and the circuit.
I didn´t find IRF-9640, so i replaced with IRF-9630, coul be this the poor sensitivity and sound that came everytime i swep the coil in one direction?
Regards
Nelson

I just saw your question. Ordinary coaxial cable....audio cable.. good shield and pvc isolated Cu wire in the middle.
No i dont think fet is the problem there. Any simillar will do.

[kuraja]

Cordius...can you please upload your .lay files of SFMD?

[nelson]

Hi hobbes and thanks for your response.
Ok, yes i have an oscilloscope, but i´m not very good with it.
One change i made is that i replace IRF9640 with IRF9630. I used a short peace of RG-58.
The detector is working, but has i posted before, with a few problems.
My electronics knolegment is very low, so i really need help from you and the experts of the forum. Of course everytime i build a nwe detector, i can get more expirence and knolegment.
This weekend i ll do some measurements with my scope.
Thank´s
Nelson

Nelson, re-posting the same questions repeatedly is not going to get you help any faster. You must provide some information for someone to work from.

Do you have an oscilloscope? If so, you may want to post some pictures of signals from your circuit. If not, it's going to be tough to help.

Adding the cable will change the capacitance in the coil circuit, so the circuit may not be properly dampened now. Also, double-check your work to make sure everything is still hooked up correctly.

If you have a scope start with the output of the NE5534, pin 6, then go from there.

[hobbes_lives]

Nelson, re-posting the same questions repeatedly is not going to get you help any faster. You must provide some information for someone to work from.

Do you have an oscilloscope? If so, you may want to post some pictures of signals from your circuit. If not, it's going to be tough to help.

Adding the cable will change the capacitance in the coil circuit, so the circuit may not be properly dampened now. Also, double-check your work to make sure everything is still hooked up correctly.

If you have a scope start with the output of the NE5534, pin 6, then go from there.

[nelson]

Hi Ivconic.
What cable did you se btw the coil and the circuit.
I didn´t find IRF-9640, so i replaced with IRF-9630, coul be this the poor sensitivity and sound that came everytime i swep the coil in one direction?
Regards
Nelson

...this is it...works more than good!
Coil is 21cm in diamm.. wire 0.35, 24 windings... 1e coin detects at 26cm distance in air, loud and clear!!!

[nelson]

Hi there, can anyone tell me what may be wrong with surfmaster PI MD
I had finish my surfmaster PI MD and i have the following questions:
1.- When i pass the coil from one side to the other, the detector only on one side and with no metal, emits a soud like the one it does when detects a metal. This is only when you move the coil in one direction.
2.- When i adjust the offset and delay trimmers, i can get two setups. one that allows you to emmit a strong sound when it detects a metal and also it makes an oscillating tone, like beep, beep, beep, about every 4 to 6 seconds depending on thrshold set. And the other way is with the thrshold very stable, no oscilating sounds, but when detects a metal, the sound is not to loud and strong. About sensitivity, the first setup is good, not the second. But has i said, everytime you move the coil, a beep, beep, beep comes thru the speaker, also in oneway pass of the coil, the MD sounds at no metal presence.
The coils is the one made by Ivconic, 21 cms in diameter, 24 turns of 0,35mm wire, inductance 355 uH and resistance 3.5 ohms.
The cable from the coil to the circuit is 50 cms long of RG-58 coaxial cable.Is this the rigth cable?
Doing test before assembled the hold unit, i got 26 cms for 22 cms copper coin. For this i just used the coil wire connected directly to the pcb and also i didn´t move the coil, just i pass a coin over the coil.
I hope my english can be understand, to get anwer my questions and doubs.
In advance, many thanks.
Nelson[/quote]

[nelson]

Hi Cordius.
I had finish my surfmaster PI MD and i have the following questions:
1.- When i pass the coil from one side to the other, the detector only on one side and with no metal, emits a soud like the one it does when detects a metal. This is only when you move the coil in one direction.
2.- When i adjust the offset and delay trimmers, i can get two setups. one that allows you to emmit a strong sound when it detects a metal and also it makes an oscillating tone, like beep, beep, beep, about every 4 to 6 seconds depending on thrshold set. And the other way is with the thrshold very stable, no oscilating sounds, but when detects a metal, the sound is not to loud and strong. About sensitivity, the first setup is good, not the second. But has i said, everytime you move the coil, a beep, beep, beep comes thru the speaker, also in oneway pass of the coil, the MD sounds at no metal presence.
The coils is the one made by Ivconic, 21 cms in diameter, 24 turns of 0,35mm wire, inductance 355 uH and resistance 3.5 ohms.
The cable from the coil to the circuit is 50 cms long of RG-58 coaxial cable.
Doing test before assembled the hold unit, i got 26 cms for 22 cms copper coin. For this i just used the coil wire connected directly to the pcb and also i didn´t move the coil, just i pass a coin over the coil.
I hope my english can be understand, to get anwer my questions and doubs.
In advance, many thanks.
Nelson[/quote]

[nelson]

Hi Cordius.
I had finish my surfmaster PI MD and i have the following questions:
1.- When i pass the coil from one side to the other, the detector only on one side and with no metal, emits a soud like the one it does when detects a metal. This is only when you move the coil in one direction.
2.- When i adjust the offset and delay trimmers, i can get two setups. one that allows you to emmit a strong sound when it detects a metal and also it makes an oscillating tone, like beep, beep, beep, about every 4 to 6 seconds depending on thrshold set. And the other way is with the thrshold very stable, no oscilating sounds, but when detects a metal, the sound is not to loud and strong. About sensitivity, the first setup is good, not the second. But has i said, everytime you move the coil, a beep, beep, beep comes thru the speaker, also in oneway pass of the coil, the MD sounds at no metal presence.
The coils is the one made by Ivconic, 21 cms in diameter, 24 turns of 0,35mm wire, inductance 355 uH and resistance 3.5 ohms.
The cable from the coil to the circuit is 50 cms long of RG-58 coaxial cable.
Doing test before assembled the hold unit, i got 26 cms for 22 cms copper coin. For this i just used the coil wire connected directly to the pcb and also i didn´t move the coil, just i pass a coin over the coil.
I hope my english can be understand, to get anwer my questions and doubs.
In advance, many thanks.
Nelson

Hi Cordius.
I had finish my surfmaster PI MD and i have the following questions:
1.- When i pass the coil from one side to the other, the detector only on one side and with no metal, emits a soud like the one it does when detects a metal. This is only when you move the coil in one direction.
2.- When i adjust the offset and delay trimmers, i can get two setups. one that allows you to emmit a strong sound when it detects a metal and also it makes an oscillating tone, like beep, beep, beep, about every 4 to 6 seconds depending on thrshold set. And the other way is with the thrshold very stable, no oscilating sounds, but when detects a metal, the sound is not to loud and strong. About sensitivity, the first setup is good, not the second. But has i said, everytime you move the coil, a beep, beep, beep comes thru the speaker, also in oneway pass of the coil, the MD sounds at no metal presence.
The coils is the one made by Ivconic, 21 cms in diameter, 24 turns of 0,35mm wire, inductance 355 uH and resistance 3.5 ohms.
The cable from the coil to the circuit is 50 cms long of RG-58 coaxial cable.
Doing test before assembled the hold unit, i got 26 cms for 22 cms copper coin. For this i just used the coil wire connected directly to the pcb and also i didn´t move the coil, just i pass a coin over the coil.
I hope my english can be understand, to get anwer my questions and doubs.
In advance, many thanks.
Nelson

[nelson]

Hi Cordius.
I had finish my surfmaster PI MD and i have the following questions:
1.- When i pass the coil from one side to the other, the detector only on one side and with no metal, emits a soud like the one it does when detects a metal. This is only when you move the coil in one direction.
2.- When i adjust the offset and delay trimmers, i can get two setups. one that allows you to emmit a strong sound when it detects a metal and also it makes an oscillating tone, like beep, beep, beep, about every 4 to 6 seconds depending on thrshold set. And the other way is with the thrshold very stable, no oscilating sounds, but when detects a metal, the sound is not to loud and strong. About sensitivity, the first setup is good, not the second. But has i said, everytime you move the coil, a beep, beep, beep comes thru the speaker, also in oneway pass of the coil, the MD sounds at no metal presence.
The coils is the one made by Ivconic, 21 cms in diameter, 24 turns of 0,35mm wire, inductance 355 uH and resistance 3.5 ohms.
The cable from the coil to the circuit is 50 cms long of RG-58 coaxial cable.
Doing test before assembled the hold unit, i got 26 cms for 22 cms copper coin. For this i just used the coil wire connected directly to the pcb and also i didn´t move the coil, just i pass a coin over the coil.
I hope my english can be understand, to get anwer my questions and doubs.
In advance, many thanks.
Nelson

350uH
3,3 ohm