experiment 1x1m coil for Surf Pi Pro

[sdesic]

I am making 1x1m coil for Surf Pi Pro
Don't know what I am going to get by making it.
No coins and little items will be detected that I know.

It has same inductance as little concentric - about 300uH.
Used network cable - 8 wires 4m long

Do I need to adjust something to use this kind of coil ?

[Jose]

1X1 mtrs coils were always a problem for me. Captan much noise, they are unstable, etc..
But I make a 1x1 mtrs coil for my delta pulse that works pretty well.
The idea is this, if you have a coil of medium size of 30 or 40 cm in diameter that works well, then try to make a 1X1 mtrs coil with the same characteristics. Ie having equal inductance and resistance.
For a coil 1X1 mts, 9 laps needed to obtain about 340 uH, but if the driver is 0.75 mm in diameter, its resistance will be about 1.5 ohms, and here, may be the problem.
Install a resistor in series 1 or 1.5 ohms to match the coil more girl that works all right.
For the characteristics of the coil 1X1 mtrs, you probably have more capacity, then you should decrease the resistance of cushioning, or install a resistor in the coil of a balor such that R together with the cushioning that is in the PCB , obtain the correct value.
In the case of Delta Pulse, I install an R 1 ohms in series and parallel 1K.
You probably have to lower the frequency and increase the TX pulse width for better performance.
At least this is what worked for me in my DP.
Jose

[Altra]

Large coils do not work well on "motion" type PI circuits. The Surf PI, Barracuda and others continually try to readjust the threshold to a null (SAT).
These circuits are designed for fast response to small items like coins. To get the a decent response with a large coil you would have to run or walk very fast. To make it work you need to either increase the RC time constant or replace the capacitor with a resistor in the SAT circuit.
This would allow for hovering over a target or slow movement. Then do what Jose mentioned increase the sample delay and adjust the damping resistor.