55W Halogen Light Mosfet Arduino Beetle

Hi guys,
first of all I'm quite new to all of this and therefore I'm wandering around aimlessly.

I want to use a Arduino Beetle and a Mosfet to regulate a Halogen Light that has 55W on a 12V System.
I'm using the D9 Pin, which I think is the same on the Leonardo and works with 4.5kHz PWM (???).

This is basically what I did. But I'm using a IRF3708.

My issue is that the Mosfet is getting way to hot and since I want to use potting compound to seal all of this, I think it won't be great to have it so hot...
Which Logic Level Mosfet do you guys recommend ?

Thanks for your help and time ! Regards!

The one in your schematic RFP30N06LE should be OK. RDS(on) 5V = 0.047Ohms. But the one you are using IRF3708 also would appear OK on paper with an even better rating at 4.5 volt.
However, I think your switching frequency may be too high meaning that the mosfet is often not fully switched. For a light, important is only that it is high enough to prevent flicker. You could also add a 150 ohm (or so) resistor in series with the gate to limit the inrush current.

Is it for use in a vehicle ? If so a P Channel mosfet may be a better choice because you can ground the light near the mounting position and run only one wire to it.

Kurtisane:
Hi guys,
first of all I'm quite new to all of this and therefore I'm wandering around aimlessly.

I want to use a Arduino Beetle and a Mosfet to regulate a Halogen Light that has 55W on a 12V System.
I'm using the D9 Pin, which I think is the same on the Leonardo and works with 4.5kHz PWM (???).

This is basically what I did. But I'm using a IRF3708.

My issue is that the Mosfet is getting way to hot and since I want to use potting compound to seal all of this, I think it won't be great to have it so hot...
Which Logic Level Mosfet do you guys recommend ?

Thanks for your help and time ! Regards!

Your halogen lamp is rated at 55 watts AFTER it has come up to operating temperature. Prior to that it is a short circuit!

Paul

Kurtisane:
...to regulate a Halogen Light...

Halogen lights shouldn't be dimmed.
Leo..

55W at 12V = 4.5A

The IRF3708 is about 10 milliohm on-resistance, so on-state dissipation = 4.5 x 4.5 x 0.01 = .2W.

However this is with the bulb filament at full temperature.

At lower filament temperatures the current will be upto 12 times larger or so, so 55A worse case. 55 x 55 x 0.01 = 30W

However low temperatures imply a low-duty cycle, so the average dissipation may be a few watts only, but
still needing a heatsink.

And all this assumes negigible switching losses, which is only true if using a gate-driver chip for the MOSFET.

And tungsten-halogen bulbs shouldn't be dimmed anyway (although its OK for fade-up and fade-down as the time is so short)

If you do use the chassis as ground return for the bulb then the high current pulses from dimming it will be imposed over the chassis and may cause issues for other equipment like a radio. If you dont then you'll need two very thick wires to supply the bulb (remember we are talking upto 50A or so peak currents).

I should explain my goal.
It is for a motorcycle with two lights. One of them is high beam and one is low beam.

The low beam is always on and the high beam ofc just when I press it. What I want to do is use the mosfet to basically wire the high beam to the low beam, but in order not do make everyone blind I want to be able to dimm it.

The reason for a microcontroller and not just a potentiometer in between is that I want to use the high beam switching (basically me pressing the high beam button) to increase the PWM Value and wrap around to 0 when above 255 (this should only apply in a programming mode).

Therefore all of this needs to be quite small, which is another issue and the reason for the small beetle.

What would you guys recommend to use for the controlling ?
Can I controll the mosfet to use it as a potentiometer ?
This would mean outputting analog signals for it to not switch on and off all the time, right ?

The whole point of the dipped beam is that its just low enough in brightness not to dazzle (and yet be visible), anything brighter would dazzle. I don't see the point of this idea, either you are dipped because someone's in front of you, or you are on full beam because noone's in front of you.

Perhaps your dipped beam bulb is under-rated?