Whites Surf PI schematic

[dbanner]

The difference can be as much as a few inches. I do not recommend this approach, but it works for me. Remember, this is self made circuit and coil. I go with whatever works in the field. The objective is not to make a perfect detector, but to find whatever treasure is in the ground.

[chuubaba]

What does "L1" stand for in this and final design. Abbreviations help if explained.

[Tim]

An attached diagram would help to explain what you are asking chuubaba. Generally L1 would be the coil, but without a diagram I cannot be certain. L usually means inductor, which could be a coil, a wound toroid, a wheel inductor(looks like a resistor),a radio frequency choke, or other winding on ferrite, ceramic, or air core.
Yes abbreviations can be confusing, especially without relevant peripheral information.

[Polymer]

I just adjust the pot while swinging a gold ring across the coil, looking for greatest depth( distance).
Every time I go to beach I do this adjustment. The pot is on back panel of my box for easy access. It's that simple.

Cool! Nice and simple. Thank you.

I am sometimes gobsmacked as to how much temperature, humidity and battery voltage influences the output of the first opamp.
Sometimes I am musing as to how much my mood effects the whole setup too ...

[6666]

The difference can be as much as a few inches.

I am frustrated and perplexed by this result, surely there must be something else going on here other than temperature ?

[dbanner]

Yes, I know. There is a sweet spot in damping where my self made surf detects at maximum distance. But I noticed it varies ever so slightly on different days. I set it up today, and maybe tomorrow is good or not so good. So I got fed up having to go inside the box and just made it on back panel of box. Those 2 extra inches are important. The other reason is that when I use headphones, I have to readjust damping compared to using the speaker that I have mounted in the box. I use small Audio transformer to drive the speaker output.

[dbanner]

My coil isn't potted in anything. It is a flat coil wound with copper wire onto ply wood and painted with kind of water seal.

[Andi68]

Were there variations in temperature?

Some components react to it

[nonkapo]

Were there variations in temperature?

Some components react to it

Yes, he mention some 12 degrees. Poor me, i dont know what to expect with my nearly 25 to 30 degrees difference in the summer months.... So in my case must be compulsory to set up such pot.
Y

[localbug]

If damping resistor gets warmer, I think higher power rating resistor should be used. Most of the electronics components are temperature sensitive, using high quality components will make your detector performance at maximum. Adding a cooler can be an alternative.

[dbanner]

I am not sure if ambient temperature is the issue here. I don't have any scientific testing like the pros in science lab. All I can say is my experience. There is phenomenon known as"ringing", which is why coil must be with damping resistor. Once she is set, it should remain, but I noticed on my self made, she is sometimes slightly off to give best sensitivity, so I tweak with pot with gold ring for best results at beach, no scope, primitive method. I am interested in finding stuff, not staring at oscilloscope the entire day. Besides I made several coils which I can adjust damping resistor easy by tweaking the pot while swinging ring for best sensitivity. Can't put scope at beach

[dbanner]

You can maybe put switch, but added capacitance is bad. The less you have between coil and her MOSFET, she is happy.

[dbanner]

Inductance doesn't change with temperature, but resistances do, so the q of coil . might change.(the parasitics)
My coil isn't potted in anything and she is not shielded, so maybe that's why she is like grasshopper
Maybe also EMI, she is not happy

[dbanner]

I just realized that I used biggish wire wound pot, maybe this is good for setting, but not good for permanent, as the pot itself is susceptible.

[nonkapo]

Sorry for the diletants question, but comparing the schematics of Baracuda and Surf PI which i'm working on together i've just notice something. The power in the surf PI is going to 7660 only after regulated to 5V by 7805, so i hope that mean any version of 7660 will work in difference to Baracuda, where the power go directly to 7660 and you need to use 7660S or LT1050 tolerating respectively 12 and 15 volts? So as conclusion 7660 or7660A will not make any difference to using 7660S or LT1050? Also if Is it possible to directly fit LT1050 on the place of 7660 without modifications(despite i do not see advantage here unlike in the Bara)?
Thanks