Whites Surf PI schematic

[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

[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?

[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.

[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.

[andrewl]

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?

[Qiaozhi]

I try with small magnet but when i remove magnet i lose all metal and coil dont detect any metal

I suggest you re-read post #1045, as you appear to have completely misunderstood the Earth Field Elimination test.

[seadoggy]

Any small magnet should be ok for the test.

I try with small magnet but when i remove magnet i lose all metal and coil dont detect any metal

[Qiaozhi]

Can i use any small magnet??,i dont have scope mate!!,i try many different coil but still problem is remain!my coil is 0.350 mh(about 23 turns wire 0.50),i have 2 board of surf pi same problem!cant search with surf pi cuz it is unstable at field

Any small magnet should be ok for the test.

[seadoggy]

If there is a beep at the end of every swing, then the Earth Field is not being eliminated correctly. You can confirm this by waving a whiteboard magnet (or similar) in front of the coil about 3 to 6 inches away. If it beeps during the test, then re-check your component values. This would be easier to debug if you have an oscilloscope.

Can i use any small magnet??,i dont have scope mate!!,i try many different coil but still problem is remain!my coil is 0.350 mh(about 23 turns wire 0.50),i have 2 board of surf pi same problem!cant search with surf pi cuz it is unstable at field

[Qiaozhi]

I think when i go outside from home with surf pi it is not stable,every time when i swing with coil make sound at every end of swing

If there is a beep at the end of every swing, then the Earth Field is not being eliminated correctly. You can confirm this by waving a whiteboard magnet (or similar) in front of the coil about 3 to 6 inches away. If it beeps during the test, then re-check your component values. This would be easier to debug if you have an oscilloscope.

[kt315]

pulse detector is sensitive to any metal like to ferrous. you have to find too clear place at first.
you have to shield the housing inside like you do that for coil too, the foil you have to connect to (-E) of battery.

[seadoggy]

i close to land -- what land??? your metals extremely overinfected yard new home? WHERE?

I think when i go outside from home with surf pi it is not stable,every time when i swing with coil make sound at every end of swing

[kt315]

i close to land -- what land??? your metals extremely overinfected yard new home? WHERE?

[seadoggy]

sorry for multiple posts guys i make this version of Surf pi.

[seadoggy]

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??