Page 16: of Marine Technology Magazine (November 2025)

LANDER LAB #16 a step up in current output. power ef? cient. Examples include Arduino, Raspberry Pi,

There are three types of switching voltage regulators: boost, ESP32, and others. Power output is limited. An Arduino I/O buck, and a combination boost-buck. A boost regulator can pin can output 5v @ 20 mA max. Make Magazine publishes step up a voltage, a buck regulator can step down a voltage, an annual Boards Guide that describes dozens of new micro- and a Boost-buck will do both. controllers and single board computers.

The simplicity of the buck design makes it more ef? cient than a boost, so when trying to put every electron to work,

MOSFET stepping down a higher voltage to lower makes sense.

MOSFET stands for metal-oxide-semiconductor ? eld-effect

Quiescent current during light-load or standby modes is im- transistor. The MOSFET has three terminals: gate, drain, and portant to consider when ef? ciency is a priority. Power to a source. MOSFETs are valued for their ability to control large voltage regulator may also be cycled on a schedule using a currents using small gate voltages, their ef? ciency, and small microcontroller controlled MOSFET.

package size. Some MOSFETs can be switched fully on by 5v (Vgs) logic levels, such as the IRL540 (Cost: $0.77). Amazon

Microcontroller sells a sampler kit of logic level MOSFETs for $19. (Search

A microcontroller is a programmable computer on a chip term in Amazon “EEEEE 70 Pcs Logic Level MOSFET”.) that offers intelligent control of a system. They are small and A small electrical signal can turn on LED lights for imaging or a motor in a pump. Great devices to know about. Google “How to Choose a MOSFET” for many good links, includ- ing videos. A helpful component selection worksheet may be found at https://www.addohms.com/mosfet-guide/.

SCR

SCR stands for Silicon Controlled Recti? er. Another three lead component, (Anode, Cathode, Gate), normally used to rectify an AC signal, has the interesting characteristic in a DC circuit of behaving like a latching relay. Consider the

NTE5455 SCR (Cost $0.80). When a 1.5v pulse is applied to the gate, current begins to ? ow from the anode to the cathode, and continues to ? ow even when the gate voltage is removed.

Current will ? ow until the current drops below a certain level, called the holding current, at which point it turns off. A sim- ple, yet reliable, time release is a small lab countdown timer that outputs a 1.5v signal to a piezoelectric beeper. Bring the

Figure 2 signal for the beeper to the gate of the NTE5455 instead to

The Addicore LM2596 Step-down Adjustable DC-DC Switching start a 10vdc source corroding a burnwire.

Buck converter can drive a 3A load with 90% ef? ciency, with excellent line and load regulation, thermal shutdown and current

Sequencer limit features. The LN2596 has an addressable minimum low

Powering up multiple parallel circuits might be challeng- power standby mode of 80 µA. (Cost: $2.48) (Photo: Addicore) ing due to initial in-rush currents. The TI LM3880 Simple

Power Supply Sequencer is a device that controls power up and power down sequencing of three independent voltage rails. By staggering the startup sequence, the instantaneous battery loads are moderated. The robust part is quali? ed for automotive applications and features a low quiescent current of 25 µA.

Transducers and Sensors

The terms “Sensors” and “Transducers” are sometimes used interchangeably, though there are subtle differences.

Sensors may be required to initiate action by the microcon- troller or dedicated circuit.

Figure 3

There are only two types of transducers. Active transduc-

A MOSFET schematic and 3-lead part in a TO-220 package. ers produce a voltage in response to a change in a parameter. (Photo: Hong Kong Olukey Industry) 16 November/December 2025

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