Whites Surf PI schematic

[Qiaozhi]

Why does the oscillator input of the 7660 need to be driven by the 555? Why isn't the internal 10khz oscillator described in the data sheet (Intersil) enough?

The oscillators also seem to have different roles. Isn't the 555's 615hz to drive the logic and coil block while 10khz is to trigger 7660's pump and transfer cycles?

In the White's Surf-PI the 7660 is not synchronized to the TX oscillator. However, if you look at the Hammerhead, you will see that the 7660 is synchronized, and the Minipulse Plus uses an LT1054 (which is a better alternative to the 7660).
This means that any switching noise generated by the 7660 in the Surf-PI, which makes its way into the receiver chain, will be asynchronous. When you sync to the voltage converter (as per the HH and MPP designs) any switching noise will get averaged out over time.

[Sean_Goddard]

Best to eliminate the 7660 altogether. I use a TLE rail splitter but a good 500mA op-amp asa rail splitter works FAR better.

[andrewl]

Thanks for referring me to the hammerhead, the pdf doc has a great explanation of the entire circuit, and addresses this question directly:

Voltage doubling by the 7660 isachieved through the use of a chargepump that must be clocked. Normally,the 7660 is used with its internal clockwhich operates at around 10 kHz, but italso has an option for overriding theinternal clock with an external one. Byusing an external clock, we can ensurethat power supply switching noise issynchronous with the sampling. R37and C11 couple the clock signal to the7660 for this purpose.

It was in search results for White's Surf Pi that I found the synchronizing connection. In the Silverdog schematic it connects to ground after passing through a capacitor. If you're not going to override the 7660's clock, why connect the OSC pin at all?

[paku]

Any one have problem with surf pi when swing coil make sound??,also when i close to land make sound my surf pi is not stable at ground to much noise make!what can be a problem??

BRO JUST TRY REMOVE 220pF

[seadoggy]

I solved problem when i SWING with coil make false sound!!,I have fix that!Now its working well.
What is best coil size and Inductance?
And how set best dumping Resistor?

[soverey]

How did you solved the problem with false sound, when swinging the coil ? , did you adjust the width of the earth sample? ( just curios )
You can find the best value of the damping resistor for a certain coil by using a variable resistor instead of the fixed one,(search damping tool on the forum) and looking at output of the pre-amplifier on the scope.

I solved problem when i SWING with coil make false sound!!,I have fix that!Now its working well.
What is best coil size and Inductance?
And how set best dumping Resistor?

[homefire]

Not sure who to give credit to on this one ? Qiaozhi ?


Try this damping resistor adjustment tool:
10k pot in series with a 200R resistor, and a 2k resistor in parallel with both the pot and resistor. This will give you an adjustment range from 181R to 1672R.
Attach your oscilloscope to the output of the preamp, and adjust the pot until you achieve critical damping. Disconnect the adjustment tool and measure the final resistance. Replace with a fixed resistor that has the closest value.

[seadoggy]

How did you solved the problem with false sound, when swinging the coil ? , did you adjust the width of the earth sample? ( just curios )
You can find the best value of the damping resistor for a certain coil by using a variable resistor instead of the fixed one,(search damping tool on the forum) and looking at output of the pre-amplifier on the scope.

I make board with error inside!!I hook up coil then i get ZERO(0) volts at NE5534 pin 6

[seadoggy]

Not sure who to give credit to on this one ? Qiaozhi ?


Try this damping resistor adjustment tool:
10k pot in series with a 200R resistor, and a 2k resistor in parallel with both the pot and resistor. This will give you an adjustment range from 181R to 1672R.
Attach your oscilloscope to the output of the preamp, and adjust the pot until you achieve critical damping. Disconnect the adjustment tool and measure the final resistance. Replace with a fixed resistor that has the closest value.

I dont have scope mate!is it possible with out scope?
I make coil 0.350 mh! size 25cm.Wire 0.60
Gold ring detect about 23cm in air test

[soverey]

I dont have scope mate!is it possible with out scope?
I make coil 0.350 mh! size 25cm.Wire 0.60
Gold ring detect about 23cm in air test

You will need scope , it makes a big difference , http://www.ebay.com/itm/HANTEK-6022B...8AAOSwHQ9WX-VE

[homefire]

That seller does not ship to the USA. I have one of these does what I need to the most parts for Detector work. For the price it works good. http://www.banggood.com/DSO138-DIY-D...-p-984002.html

[seadoggy]

This is my Surf PI.
Coil is 0.350mh size 25 wire 0.50
Coil dont have shield!!,next coil i make with ALU foil and see what will happen.

[bernte_one]

Looks goods, but i suppose with massive alu foil schield you will loose sens.
Try to use shield foil from ftp Network cable, mix graphit powder with clear laquer (simple and cheap graphit paint)

[seadoggy]

Looks goods, but i suppose with massive alu foil schield you will loose sens.
Try to use shield foil from ftp Network cable, mix graphit powder with clear laquer (simple and cheap graphit paint)

I will try use foil from block capacitor that foil is very thick!
If i use graphite what resistance must be??

[paku]

You will need scope , it makes a big difference ? HAHAHAHAHAAHAH