A mini 5V push-pull solenoid will be used to press the button on the front of the surveillance server.

The solenoid is an electromagnet. The metal rod in the center is called an armature. It will be drawn into the solenoid when power is applied to the coil. When power is cut, the spring will return the armature to its starting position. The solenoid draws 1.1A which is much more than the GPIO pins on the Feather can source or sink. Therefore, a logic level N-channel MOSFET will be used to drive the solenoid.

The MOSFET can act like a switch.  When voltage is applied to the gate pin it allows current to flow between the drain and the source pins.  An IRLB8721  is selected because its gate can be driven at logic level voltages such as the 3.3V GPIO pins of the nRF52840 Feather.

This guide was first published on Oct 16, 2019. It was last updated on Oct 16, 2019.

This page (Solenoid & MOSFET) was last updated on Oct 15, 2019.

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