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I am looking to use a MOSFET to switch a linear actuator on and off. There's nothing else on the circuit, just the switch and the actuator (and a Raspberry Pi to control the switch.)

The actuator takes 7.8V to engage and draws 1.26A of current. There's no datasheet for the actuator so those are all of the numbers I have.

  • How do I pick the right MOSFET?
  • What are important variables to consider?
  • Is there some sort of website that I can use to filter through all of the options based on those variables?
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    \$\begingroup\$ A bit of advice: for mosfets as switches, the drive voltage should be taken from the rds,on spec, where it says what the Vgs used was. That will give you a safe drive to use \$\endgroup\$ Sep 14, 2021 at 23:08

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Picking the right Mosfet

Theare are several basic tutorial with the topic "Using MOSFET as a Switch", for example this one or this.

The minimum parameters you should consider are:

  • VDSMAX: Choose it higher than the supply voltage. 60 V mosfets are commonly available.
  • Vgs th: Control voltage. If you are using a RPI, the outputs are 3,3 V so pick something that can turn ON the mosfet. Check charts VDS Vs ID parametric depending on Vgs
  • RDS on: The smaller, the lower the conduction loses.
  • Add a freewheeling diode to the actuator in order to protect the mosfet.

Websites to filter

You can perform a parametric search on any electronics component dealer: Mouser, newark, digikey...

Example With that in mind, a couple of examples: Mosfets: PMV37ENEAR (SMD) or IRFZ24NPBF (Through hole) and for diode 1N4001 will be enough. Asuming you are not doing PWM.

schematic

simulate this circuit – Schematic created using CircuitLab

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  • \$\begingroup\$ Asuming you are not doing PWM. You can do PWM even with "slow" components, just keep the PWM frequency low, like lower than a few kHz. Realize that if you do that, you might hear (as a sound) that PWM frequency. \$\endgroup\$ Sep 15, 2021 at 7:17

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