P-channel mosfet 27A 60V added opto coupl question

Hi everybody,

I want start using following MOSFET'S

https://www.sparkfun.com/products/10349

This is the first time i work with MOSFET'S but i really don't have any clue how to hook them up, how they interface with the arduino boards,... i read already a couple of tutorials but most of them cover the N-channel mosfets and because mine are specifically used in automotive projects i need P-channels.

so my questions are.

  1. how do i hook them on to my arduino board? do i have to put a resistor between my output and the gate? or do i have to ground the gate true an resistor? if yes which value of transistor i have to use?

  2. which code i use to conduct the mosfet? do i have to switch the output high or low?

  3. which things i have to keep in mind? due to connection, programming...

thanks in advance

best regards

jazzy

That MOSFET isn't logic-level so you cannot drive directly from the Arduino, it needs -10V of gate drive (relative to source).

What are you trying to do? p-channel FETs are usually used for high-side switching, and this device would be fine for switching 12V supply in-line if driven via a small signal NPN level-shifting transistor....

Hi,

what i would like to do is make a board computer for my motorcycle. to switch all the consumers such as head lights, rear lichts, indicator lights, horn,... i want to use mosfet's but i need P-channels because all these consumers use the motorcycle's frame as GND. i really don't know where to start due my lack of knowledge from mosfets. i used to do this with a combination from an PNP and NPN transistor circuit but this is a circuit which take a lot of space on my PCB that's why a want to use mosfet's. the current i want to switch is between 1 and 5 amps.

best regards

Then the way is to use a small NPN transistor to drive the p-channel gate (which also has a pull-up resistor of about 1k between gate and source). When the NPN is on it pulls the gate to 0V, and since the source its at +12V, the Vgs becomes -12V and switches on the p-channel.

To drive an NPN you need a base resistor of about 1k, emitter to ground, collector to the p-chan gate. 1k between p-chan gate and source, source to +12V, drain to load positive...

(plus some protection circuitry to stop voltage spikes blowing the p-channel gate oxide - typically a 16V zener across gate/source)

Ok thanks!

you mean something like this?

when i see to the symbol from the mosfet a want to use (see sparkfun link)
it seems the protection diode is already forseen is that true?

best regards

jazzy

Not quite, the zener protects the gate-source circuit, not source-drain. Also you'll need another resistor to limit current through the zener... If you exceed gate-source voltage you can punch a hole in the few-atoms-thick layer of silicon-dioxide gate insulation - a zener should clamp any stray voltage spikes (mount it on the terminals of the MOSFET, not remotely).

The more power you switch the greater the chance of induced voltage spikes, also the supply may be quite dirty too.

Thanks mark.

later i’ll add an other schematic. i also want to use an opto coupler i’ll integrate that too in my shematic maybe you can also take a look to that please?

the value of the resistor to limit the current through the zener? which value i needs to be aprox?

best regards

Hi everybody,

so now i added an 4N35 optocoupler. before i want to order and burn up any parts wil this work with currents from 0 - 3 amps?

best regards

4N35 optocoupler

I would add a 100K resistor from the Opto Isolator pin 6 to 4 Unless you need to connect 0V of the 12 volt supply to Arduino GND, don't.

LarryD:

4N35 optocoupler

I would add a 100K resistor from the Opto Isolator pin 6 to 4 Unless you need to connect 0V of the 12 volt supply to Arduino GND, don't.

yes the 12V gnd is connected tot the arduino 5V gnd so i can leave pin 6 from the coupler untouched or do i have to ground it too?

best regards

jazzy G