id like to be able to drive and use pwm to control fan speed on a 12v fan the fan also draws around 8 amps cont i was looking at FETs for driving the fan is this the wrong direction to go thanks in advance
is this the wrong direction to go
Not at all: for 8A, it's pretty much the only way to go.
Make sure you use a "logic level" FET: most power FETs are designed to work with voltages more on the order of 12V or higher, and don't fully turn on with a 5V gate signal.
You can also add a pre-amp stage (a simple transistor pre-amp will do) before sending the signal to the gate of the MOSFET.
im new to all this and im trying to learn so thanks for the help guys
one last q
does anyone have any info on what fet will do?
thanks in advance spooks
There are many FETs out there that are "suitable". Which you pick depends in part on where you're shopping.
The IRLnnn series are, afaik, all logic level (I think that's what the "L" stands for), and available both from suppliers like Digi-key and, sometimes, from surplus sources.
You want to look for a low RDS(on), because that reduces the amount of wasted energy that you have to dissipate as heat.
The IRL2703 and IRLZ44 have very low resistance, and there's an IRLZ44Z that's even lower (low enough that you could get by without adding a heatsink). And fairly cheap from Digi-key.
Hi,
I faced similar issues. Take a look to the BTS555 or BTS441, which are capable to do the job.
Features like Overload protection, Overtemperature protection, Fast deenergizing of inductive loads (dump load) will help easy usage.
They are not cheap, but a lot of functions included!
Just to add to your choices: I've used the FQP4N20L, of which there are a few in the series (different current ratings). Not sure what your starting current is.
These FETs have avalanche protection.
My only regret with these is that I didn't notice until afterward that the heatsink is electrically connected to the drain - led to some increased difficulty in isolation.