What are some common devices that can be used for general circuit protection?

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We have FAQs about inrush current and protection for power supplies, but for many projects, there is a need for general circuit protection and protection from power supplies.

Fuses are inexpensive and easy to work into designs, as well as safe, reliable, and have low resistance/high efficiency. It is important to note that fuses do not prevent faults, but they are a great way to protect your circuit, and are easily replaced when the original fault is found and repaired.

Schurter 8020.5076 Fuse
Schurter 8020.5076 Fuse

Radio-Frequency Interference (RFI) Choke will protect from RFI and EMI from external sources like radio transmitters, motors, solar flares, etc but won’t protect against shorts and surges. Capacitors can filter incoming power as well which helps with the noise induced between the DC output of your power supply and your circuit. Like chokes, capacitors would not protect against current spikes and short circuits.

TDK Corporation ZCAT3035-1330-BK Filter
TDK Corporation ZCAT3035-1330-BK Filter

Diodes are very useful for protecting circuits from reverse current as they allow current to flow in one direction only. If a reverse polarity voltage is applied to your circuit, the diode will keep current from flowing in the wrong direction provided that the applied voltage is not above the breakdown voltage. In that case your circuit would likely be fried regardless of the polarity. A small issue with diodes is the small forward voltage drop of the diode, which is subtracted from the voltage applied across it.

NTE 1N4005 General Purpose Diode
NTE 1N4005 General Purpose Diode

Voltage Regulators can also protect circuits from reverse polarity as well as overvoltage (obviously), thermal protection, and provide current limiting. There are many specifications for voltage regulators when compared to fuses and diodes, so check what your design will need before selecting one.

Renesas ISL80136/38 Linear Regulator
Renesas ISL80136/38 Linear Regulator

SWITCH! It is easy to forget the the basic switch as a circuit protection device, since we typically think of it as a control device. However, it also allows us to prevent any power to come into your circuit before it is in a ready state. It also allows us to prepare any other safety measures such as fire extinguishers, PPE (personal protective equipment), and clearance for any mechanical gear controlled by your electronics.

C&K DM64 Double-Pole Rocker Switch
C&K DM64 Double-Pole Rocker Switch

Another physical protection for your circuit or device is a polarized connector. This is a connector that is keyed or shaped in such a way so that you cannot apply reverse polarity to your device. Typically these types of connectors also provide locking to prevent an unexpected power cut. Choosing a specific connector may also prevent connecting a supply with the wrong specifications for your device.

JST-PH Male to JST-SM Female Adapter
JST-PH Male to JST-SM Female Adapter

These devices and others can protect your circuit from damage inflicted by the many types of faults that happen everyday. So be sure to use one or more to keep your circuit functioning properly!

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Authored By

Gary Crowell

Avid biker, audio enthusiast, tinkerer, and radio/autonomous car racer. Also work with PCBs, electronic/mechanical design, and programming, so I really get interested if the project is mechatronic.

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