Whites Surf PI schematic

[chemelec]

Nice pics. Do you're in Chile before the earthquake? My daughter visit Chile for 15 days and 15 days after the earthquake occurs...

Esteban, The Earthquake occured 9 days after we came home.

[Esteban]

Having some Spare Time and just using part I already have, I tried this:

http://www3.telus.net/chemelec/Surf.Temp/

Works pretty good.

Also, if anyones interested, about 800 Pictures of my recent trip to Chile, Argentina and Brazil.
Link on my Home Page.
http://www3.telus.net/chemelec

Nice pics. Do you're in Chile before the earthquake? My daughter visit Chile for 15 days and 15 days after the earthquake occurs...

[chemelec]

Having some Spare Time and just using part I already have, I tried this:

http://www3.telus.net/chemelec/Surf.Temp/

Works pretty good.

Also, if anyones interested, about 800 Pictures of my recent trip to Chile, Argentina and Brazil.
Link on my Home Page.

http://www3.telus.net/chemelec

[TH Jim]

Update on the pulsing audio problem

Hi All,

Further to my last post about the annoying audio pulsing business, I have found that adding a small amount of capacitance (470pf) between the the 12v rail and the emitter of Q6 stops the pulsing. Havent tried any smaller values - it might be possible to get away with less than 470pf.

This has really helped in tuning up, making the delay and offset adjustments much easier, resulting in better performance.

Hope this helps

[Coe42]

Thank you!

Thanks Fred!

[Fred]

Hi Black, I 'm a little confused and I hope you can help me. I'm trying to transfer your schematics to a pcb using the toner transfer method. When I hit the 'print' button in the program (Sprint-layout) do I have to mirror the image that appears there or it is already mirrored?

Thank you!

Hi,
I am not Black but i use Sprint layout, you don´t need to mirror (mirror mark unchecked).

[kt315]

the schematic you asked me for.

[Coe42]

Mirror or not?

HI. I'M TURKISH. MY SURFMASTER PROJECT VER. 1.1

Hi Black, I 'm a little confused and I hope you can help me. I'm trying to transfer your schematics to a pcb using the toner transfer method. When I hit the 'print' button in the program (Sprint-layout) do I have to mirror the image that appears there or it is already mirrored?

Thank you!

[bklein]

I'm just throwing this out there without trying anything - but I see several instances where people have the first sample occurring far past the edge of the flyback "edge". So by that time coil speed seems like irrelevant as the sample is occurring so far past the first valid data. We used beads on guitar amp inputs and had no visible or audible negative effects. High impedance inputs with similar gains.... just my first thoughts, no worries if I get shot down by theory or example...


Barry

[TH Jim]

Yes there is definately noise getting in through my coil as well, But what can you do about it without affecting the reflected pulse? I did read somewhere on this forum about someone using a Balum transformer to eliminate noise in the coil / cable, but dont know what results were like.

I have 1 bead on +- shielded coax that delivers power from my hip mount battery pack and another on a similar cable that returns the audio signal to the battery pack (where my headphones plug in).

Regards, Jim.

[bklein]

Thanks for the tip!
I haven't looked at eliminating the noise in mine yet but I had thought it was getting into the coil itself as if I moved its orientation it would affect the noise amount. The SD2000 schematics on site have a 1uH inductor in series with the coil. I think something can be done but I haven't looked at just what yet. Did you put one bead on the ground/shield as well?
Some op amps like to rectify rf thus you hear it. Problem with guitar amps. I lost track of which op amps don't do this... too long ago for me.

[TH Jim]

The beeping problem solved

Hi Guys,

Reading through some of the earlier posts in this thread I realised that a few of us have experienced the strange audio pulsing at anything from 1/2 second to once every few seconds. Anyway I think i've found the cause - it's RF / mains hum getting in through the headphone cable (or battery cable if its long like mine). To kill off this interference just put ferrite beads on your cables near to where they connect to the PCB - it worked for me

P.s Don't put ferrite breads on your coil cable - that will be bad

[bklein]

Ok, no comment means my brain cells are screwed up...
I temporarily fixed that and can now see things line up as I would expect to see.

[bklein]

I have attached delay.jpg to demonstrate my problem understanding the preamp circuit. You can see that the input and output are delayed by at least 6uS. Perhaps this is due to op amp slew rate? This is not a coil speed issue but a circuit delay we'd rather do without. You can see that I have reduced the op amp gain considerably by replacing the 1K neg. input resistor with 100K. I also deleted the input diodes to negate the weird things I was seeing with them incircuit. Maybe this makes sense to you guys, but not to me....

Barry

[porkluvr]

Barry has informed me that the LM358 model was left out from my project post. Here it is, along with appropriate symbols.

Most IC manufacturers have models for at least some of their devices on their websites. Many times the model's pinout will be exactly described in the model's header. If not, well then it may be time to exercise one's cursing skills.

So you then need a symbol. All that is often needed is copying a similar symbol and making the appropriate attribute changes to match the new model (and of course renaming the copy with the appropriate filename). New symbols aren't hard to make, either.

LTspice will need to be restarted before you will be able to use new symbols, or before changes to various .cmp files will be recognized.