Whites Surf PI schematic

[TH Jim]

Setup without a scope

Hi Guys,

I have been testing a few different coils on my surf pi and have no oscilloscope to help set them up. I have noticed that the offset of the 5534 needs to be set differently for each coil to achieve max sensitivity, and a value of 0v on the output is not necessarily best. For most of my coils the position it is most sensetive is with a DC of around 2v on the output of the 5534.

I have been monitoring the output of LM358 - pin 7 and noticed that if the voltage on this pin is any greater than 3.7v then the audio becomes dull and fuzzy and the detector stops responding to targets. Both the Delay control and the 5534 offset affect the voltage on LM358 pin 7 and I have found that the shorter the delay setting the higher the voltage. So I have tuned up by gradually setting the delay to a lower value, then adjusting the offset, then the delay again (all the while making sure the output on LM358 pin 7 stays below 3.7v) until the delay is at minimum setting and there is about 3.4v on pin 7 of the 358.

At this point the machine responds quite well to small gold rings and seems to be about as sensitive as i can make it. The DC value on the output of 5534 is anything from 0.5v to 2.5v depending on the coil.

This is a preliminary finding and i'm gonna do a lot more testing to nail this down, but in the meantime I would be interested if any of you guys could verify these results on your own detectors, make any comments or suggestions for a better methods of tuning.

I am thinking that maybe my coils are a bit wide of the desired inductance and hence the need to set the offset away from 0v ?????????

Regards Jim.

[bklein]

Tina does have a 4093 so maybe worth giving a shot again....

[porkluvr]

Is this tina something new or has it been around awhile?

It's been around. I remember some years ago that Tina offered a demo version. Supposedly, it was full featured EXCEPT for not allowing the victim to SAVE a simulation file. (They were so, sooo generous.)

After about two days I felt like a crash test dummy. (Keyword: dummy.)

I threw it away, picked up LTspice and never looked back.

edit: A few years later Texas Instruments adopted hamstrung version of Tina as their product simulator. I'm sure it has been improved in the meantime but I got thwacked once already.

I just wish that there was an easier way to run logic circuits than what is afforded with LTspice. There are a good many CD4000 and 74HC family models available, but schmitt trigger device inputs are implemented inaccurately. That makes trying to simulate the Anchor Baracuda, and even the Whites Surfmaster (out past the 555 circuit) go very badly.

[bklein]

Is this tina something new or has it been around awhile?

[A Gumby]

To chose the proper dumping resistor, I use a (power) potentiometer and a series resistor for the minimum value (let’s say 150 ohm) instead of R6.
Put the probe of the oscilloscope (yes, an oscilloscope is needed…!) at the output of U2, pin 6 of NE5534, and gradually lower the potentiometer value until all the spikes disappear. See the image below.
Disconnect the potentiometer, measure his actual value and replace it with a fixed value power resistor.
That’s all.

As a matter of fact, that's exactly what I'd planned to do to check the accuracy of TINA-TI. I'll be using a pot with a low value resistor in series.

[Alexismex]

Very nice animation and complete info for the novice ,thank you noemio for this good post.
alexis.

[Noemio]

The way I chose dumping resistor

To chose the proper dumping resistor, I use a (power) potentiometer and a series resistor for the minimum value (let’s say 150 ohm) instead of R6.
Put the probe of the oscilloscope (yes, an oscilloscope is needed…!) at the output of U2, pin 6 of NE5534, and gradually lower the potentiometer value until all the spikes disappear. See the image below.
Disconnect the potentiometer, measure his actual value and replace it with a fixed value power resistor.
That’s all.

[A Gumby]

Surf PI coil drive simulation

Here a Surf PI coil drive simulation file to use with the the free TINA-TI analog simulator found here:

http://focus.ti.com/docs/toolsw/folders/print/tina-ti.html

Use it to play with coil variables and damping resistors.

[Wilson]

Falcon OK, please send me by email.
Thanks.

[Falcon]

Who sent me the project (SURF PI) was "Dirceu"which also participates in this FORUM (http://www.geotech1.com/forums/showt...t=13810&page=8), but he made some changes (do not ask me how and where because I'm an amateur at it, hehehe) if you want I can send you by email.

[Wilson]

Google Tradutor


Hello Falcon, but I am Brazilian! the project that you're riding seems to be better, I've researched and hardly reaches a depth that you mentioned, hopefully that works.
25cm in the air I got a gold ring on the threshold of audio.
Which project are you riding? please let me know.

[Falcon]

hi Wilson!

you are Brazilian? (I am)
you made these changes greatly improved performance? (depth of search)
I have a project that finds a £ 1 coin (real) to 37cm (not yet finished this, but the inventor of the project says yes)
yours is better?

[Wilson]

Tradução do português para inglês

Hello, I built the Surf-Pi and replaces by NE5534 TL081 "Remove P1 ofset" also replaced by LM358N TL082.

Replaces
R18 47K to 820K
R9 1M to 2M
R2 3K3 to 10K "553Hz"
R6 390R to 680R "Damper"

Inserted in series "R22 100K" potentiometer 100K "GAIN setting outside panel"

P4 eliminated and Speaker, one installed at the site Twiter Piezo transformer internal low power.

21cm wire coil 19 turns 0.5 mm

Also rode a 18cm x 18cm square coil 20 turns 0.5 mm wire worked very well, I'll ride with PVC pipes and connections 1 / 2 "rod and 3 / 4"

The operation with the coil in the air and the exchange of the components mentioned above was very good, I know that IC is not exactly the same but worked better than the original with more sensitivity.

OBS:Not tested in field

Wilson

[konan]

Complete detector. It works well except that I have two problems.

1) Review with the photolith pen, the tracks are very close to each other.

2) The detector after 15 minutes it begins to make strange noises.

3) I can not put 12V, starting a sound impossible to be silent. I have to feed 11V to operate.

Anybody can help me find out what is going on?
a copy of it.

not corect

[TH Jim]

Could be possible, my surf pi reacts to bricks buried on the beach.