Dumping resistor heating

[ionut_mtb]

https://youtu.be/c_uwIzDE4bA

[ionut_mtb]

I don't know why the photos are upside down, in my phone are normal.
Kt i don't understand what you mean. Pps is high, not sure exactly, i was aiming 10000pps like goldquest ss, but my tx pulse is 60us not 40.

[kt315]

you do a mix? 4khz pps?

[ionut_mtb]

Dumping resistor is good, flyback voltage looks like 250v ? (New scope, digital). Resistance of the coil is 1.6 ohm and dumping 360ohm. Like i said pps is quite high, helping with stability, noise and good depth on gold.

[kt315]

overdamping R value?

[waltr]

This is a surfmaster pi with modified timings, tx pulse 60us, prr 248us. Coil has 280uh with 24awg wire. Mosfet is warm with the heatsink but dumping resistor become very hot. I think is 3w, not sure. I don't have tool to measure consumption wich i assume is very high. What should i do, buy a powerful dumping resistor? Any advice? Decreasing prr may give depth reduction.

I know is crap, but this is one of my first detectors made and looks like this because it need to fit exactly in a small ikelite waterproof enclosure. Performance is what matters. Anyway i don't do pi detecting and is just a way of spending time in long cold winters.

First is to look at the Coil switching, on & off, with an O'scope. Ensure the Damping R value is correct.
If this is correct and the Coil fly-back ringing is critically dampened then unsure what to do. Possibly just add some series R to the coil to decrease Peak current.

My guess is that you will see on the O'scope some pretty ugly stuff due to the Mosfet leads and other Bad layout.
Grab and post some scope pictures for us to look at.

[ionut_mtb]

garbage. sorry but your board is one.
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Janne Peltonen. uses CAD, makes perfect PCB. SHE IS FEMALE.

SIC! female!

I know is crap, but this is one of my first detectors made and looks like this because it need to fit exactly in a small ikelite waterproof enclosure. Performance is what matters. Anyway i don't do pi detecting and is just a way of spending time in long cold winters.

[kt315]

garbage. sorry but your board is one.
----


Janne Peltonen. uses CAD, makes perfect PCB. SHE IS FEMALE.

SIC! female!

[ionut_mtb]

This is a surfmaster pi with modified timings, tx pulse 60us, prr 248us. Coil has 280uh with 24awg wire. Mosfet is warm with the heatsink but dumping resistor become very hot. I think is 3w, not sure. I don't have tool to measure consumption wich i assume is very high. What should i do, buy a powerful dumping resistor? Any advice? Decreasing prr may give depth reduction.