Help with modifications on PI

[MDfanatic]

Hey guys, I'm a newbie in electronics and I need some help.

Although I'm just getting the hang of it, I need some help to understand how a mosfet affects the pulses on a coil.
For example I have IRF840 which has an output power of 125W and Maximum Drain Current 8A, If I replace it with 30N50 for example that has an output power of 300W and Maximum Drain Current 30A, how will it affect the coil (at least 1.5mm core thickness)?

And another question, Is there a way that I can separate the transmitter and receiver coil and if so, what modifications would be needed?
I have a Clone PI-W and I would like to separate the Transmitter and Receiver in two different coils, is it even possible?


TL;DR: If I replace IRF840 with 30N50, what would the advert effects be, if any? Can I split the Tx/Rx of a PI metal detector in two loops?

Thank you guys for your time, any help would be much appreciated!

[waltr]

Most likely the MOSFET change will not effect the coil pulses.
Think Current through the coil not Voltage across the coil.
The total series resistance has a big effect of peak coil current.
If a different MOSFET's RDon is less then there will be more current into the coil but the coil resistance will to larger anyway.

Then there is Tau = L/R, The coil's time constant and the exponential charge curve.

Lastly, there is the MOSFET's Avalanche breakdown Voltage which comes into play with the kick-back Voltage.

Keep reading thread is this forum and then build and experiment to get a better understanding.

Yes, it is reasonable to have an TX and a RX coil on a PI detector. This is what I use.
Check my build thread on details of an IB coil for a PI.
https://www.geotech1.com/forums/show...ake-on-the-HH2

[kt315]

Thank you guys for your time, any help would be much appreciated!
---
good request amigo. i must say if you change your old wife on new one you get just same holes in same places.

[MDfanatic]

waltr I'm really glad you answered because your take on HH2 was my inspiration to the current project I'm working.
What I'm actually trying to do is convert HH2 to DSP and use a 40" concentric coil with an inner 15" coil.

That would take a lot of time and effort but I think it would be worth the trouble for bigger size targets.

kt315 hahaha good one
But the new one might have deeper holes hahahaha

[waltr]

I have been working on code for a PIC32 for timing control and signal processing.
Still no where near near enough to use.
I did post the code here:
https://www.geotech1.com/forums/show...ng-in-hardware

What are your ideas on DSP? Lots of different ways to analyze RX signal.
This might be a good topic for the 'Programming' section.

My favorite coil on the HH2 is the 8" concentric. Deep and selective.

[Sean_Goddard]

KT315 how true and PMSL at the analogy. NICE ONE!!

[ivconic]

But what is someone wants to exchange his 40 years old one for two 20 years old ones?
Generally it think this is splendid idea!