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### Topic: Which mosfet to use with 4 TEC1-12709 peltiers (Arduino MEGA 2560 board) (Read 972 times)previous topic - next topic

#### projectspotter

As the title says really,

I'm going to powering 4 peltiers (TEC1-12709 136.8W 12V 9A TEC) and I need to know what MOSFET type to use. I'm quite inexperienced with electronics so if you know a mosfet and model number I'd be super appreciative!

ProjectSpotter

#### MarkT

In series or in parallel?  Using PWM?  If so what frequency?  Higher speeds of PWM would
really need a MOSFET driver chip to get fast switching.

If you want to drive the MOSFET directly from an Arduino you _must_ get a logic-level FET.

What maximum current are you needing and what's the power supply(see my first question)?  You need to calculate
the power dissipation in the FET using I-squared-R (ignore the nominal current rating of a MOSFET,
its only applicable if using extreme cooling measures).

[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

#### projectspotter

In series or in parallel?  Using PWM?  If so what frequency?  Higher speeds of PWM would
really need a MOSFET driver chip to get fast switching.

If you want to drive the MOSFET directly from an Arduino you _must_ get a logic-level FET.

What maximum current are you needing and what's the power supply(see my first question)?  You need to calculate
the power dissipation in the FET using I-squared-R (ignore the nominal current rating of a MOSFET,
its only applicable if using extreme cooling measures).

Some of this has gone a bit over my head, this one of my first projects so apologies for my ignorance

The peltiers will be in Parallel, I don't know if I would be using PWM (should I use PWM?). Frequency wise I'm not sure.

Maximum current would be 28A, the power supply would be a max of 550W but in reality the power draw will be closer to 335W.

#### MarkT

OK, so you need a very low Rds(on) device - heat dissipation is I-squared-R, so if the device were 10 milliohm that
would be 8W dissipated when on, which would need a reasonable amount of cooling (something like a chipset
heatsink and fan perhaps?).  If you got a 3 milliohm device you'd run a lot cooler or need less heatsinking.

I've used an IRLS3036 in the past, its logic level, has 60V rating and 2 milliohm.  However its surface-mount only.

I'd recommend trying to get a device with Vds voltage rating of 20V or more, about 5 milliohm Rds(on) or thereabouts
and logic-level - TO220 package is probably easiest to heatsink (remember the drain terminal is also connected electrically
to the tab, so you need an insulating heat-conducting pad between package and heat-sink.

Another approach is to parallel a couple of devices to get half the Rds(on) figure - then 10 to 15 milliohm devices
would be more feasible.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

#### projectspotter

OK, so you need a very low Rds(on) device - heat dissipation is I-squared-R, so if the device were 10 milliohm that
would be 8W dissipated when on, which would need a reasonable amount of cooling (something like a chipset
heatsink and fan perhaps?).  If you got a 3 milliohm device you'd run a lot cooler or need less heatsinking.

I've used an IRLS3036 in the past, its logic level, has 60V rating and 2 milliohm.  However its surface-mount only.

I'd recommend trying to get a device with Vds voltage rating of 20V or more, about 5 milliohm Rds(on) or thereabouts
and logic-level - TO220 package is probably easiest to heatsink (remember the drain terminal is also connected electrically
to the tab, so you need an insulating heat-conducting pad between package and heat-sink.

Another approach is to parallel a couple of devices to get half the Rds(on) figure - then 10 to 15 milliohm devices
would be more feasible.

Ok awesome, thanks for the help. Just to check so if I did a 2 x 2 series/ parallel then I would only need a mosfet rated for a 30V and 19A max correct?

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