2nd Surf PI board problem ?????

[plumabob]

I recently completed my 2nd SPI board. Never was able to get a threshold but I can detect a target, just no threshold at all. I've checked every part and all is well. I'm missing something but for the life of me I can't figure out what. Now today out of desperation I popped out the the LM385 and installed a LM833N and finally got threshold but it is erratic and comes and goes but is partially adjustable. Funny thing is that it detects much better with the lm833N. Now the lm385 is good as I have tested it on my working board.

Any ideas???

[kt315]

Greener Living, More Noise

my english is poor to reply... Eric I hope will give you a lesson about noise problem in room...

http://www.findmall.com/read.php?34,...00#msg-1212800

Greener Living, More Noise.
Posted by: Eric Foster [ Send a Message ]
Date: May 10, 2010 05:12PM
Moderator
Registered: 5 years ago
Posts: 293
I have converted one of my rooms at home into a supplimentary workshop for PI tests and experiments. Here I have been working on a low noise front end but was puzzled as to why the noise level went up considerably in the late evening. Changing the coil orientation did nothing as did neither switching off computers and TV etc. Anyway, the bulb in my bench light needed replacing, so I got one of the 15W energy saving bulbs that we are now encouraged to use instead of the filament type. Switching the light on to examine some parts on the circuit board caused the noise to almost double. I then went round the house switching off all the lights which are of the energy saving type. The noise dropped right off, which explains why it always happened late evening. The final noise source turned out to be the energy efficient central heating boiler. Off this went and the detector threshold was now as smooth as silk. Looking at this noise on the scope, it has a mushy noise envelope which seems to repeat in sympathy with the line frequency, and I assume that the wiring and piping around the house radiates it like an antenna. Hence I couldn't get rid of it by changing the coil orientation. Also I could detect the noise from lightbulbs downstairs at the other end of the house. I use energy saving bulbs in my bench lights at my main workshop which maybe accounts for some of the noise I get there. Just something to look out for if you do home experimenting on PI detectors.

Eric.

[chemelec]

I have had Numerous, Simular problems!

Might make you wonder what all this radiation will do to our bodies over a lifetime?

My Computer in my workshop Also interfers with some of my tests!

[taliesin]

I have had Numerous, Simular problems!

Might make you wonder what all this radiation will do to our bodies over a lifetime?

My Computer in my workshop Also interfers with some of my tests!

i don't know what i'd do without my 50 hz eddy current coat i wear in the house

[mikebg]

i don't know what i'd do without my 50 hz eddy current coat i wear in the house

Instead 50Hz coat, I use "all Hz coat" for metal detectors :-).
This is the TWIN LOOP configuration of RX coils. It can suppress even the GND signal.

[plumabob]

I asked for help with my surf pi. What is all this noise discussion? Please start another post!

[taliesin]

Instead 50Hz coat, I use "all Hz coat" for metal detectors :-).
This is the TWIN LOOP configuration of RX coils. It can suppress even the GND signal.

are they in phase mike?

[taliesin]

I asked for help with my surf pi. What is all this noise discussion? Please start another post!

it may be noise is your problem plumb

[plumabob]

Nope noise is not the problem. My working SPI runs great. Coils are shielded also. Really would like to know if the LM833 could work in the SPI as my depth more then doubled or where to troubleshoot next. Just looking for some help here not noise...LOL

Bob

[kt315]

I asked for help with my surf pi. What is all this noise discussion? Please start another post!

no problem. any your caprice for your money. so we say here.
i am ready to help you... to write: in PM.

[taliesin]

i used a BA728 for that part.i'll try some others when i have a chance and see if it makes any difference.

[taliesin]

sssssshhhhhhhh no noise Bob don't like it

[Vortxrex]

HI Bob, what happened when you installed the LM833 in your working board? are you saying it increased the depth (over the 15" you were getting on a US Nickle)? I think if you could get your scope working & show some test point waveforms that would really help find out what is wrong w/ your second board.

Dave Frank

[plumabob]

No Vortxrex,

It doubled what I was getting with the faulty board. I really wish I could get my scope going but I'm not having any luck at all. With my good board all it did was give me a constant unadjustable threshold. It was too loud to check any targets. I'm guessing with the right resistors and caps perhaps the LM833 could show some depth gains. I wish I understood electronics better but I do not. I'm probably wrong. If I could just get my 2nd board working correctly at this point I'd be happy.

Bob

[bernte_one]

hello bob

maybe you have killed a part while soldering, this weekend i touch a mks cap with my solder iron autsch i dont see it first time but i have wondered why it smells like plastic most mistake are the basic ones you dont think about make a makro photo from your solder silde of pcb and check it with zoom on pc monitor the same with the other side of pcb that elps me sometimes in past better then any magnifying glass every part on right place?