Engineers must protect their electronic systems. Thus, we frequently get requests for tips, tricks, and insight on the topic. For instance, a UK-based community member recently requested some insight into electronics protection and bullet proofing. We provided him with the content below. And now we want to pass it on to you as well.
Circuit protection is necessary to ensure that a circuit will work reliably for 10 years and beyond. Input power supplies are susceptible to spikes from various sources including lightning, high-power machinery (e.g., generators and motors), or interference from outside sources (e.g., microwaves). The figure below shows one way to provide circuit protection. If a voltage spike is applied at VIN, the metal oxide varistor (MOV) will act at 18 V and the positive temperature coefficient (PTC) fuse will limit the current drawn. A transorb (transient voltage suppressor), which can be thought of as an ultrafast silicon zener diode, can be used in place of the MOV. Also, a capacitor in parallel with the MOV will soak up fast transient spikes—an electrolytic capacitor for low-frequency transient voltages and a small-value ceramic capacitor for high frequency transient voltages.
Editor’s Note: This EE Tip was written by Fergus Dixon of Sydney, Australia. Dixon, who has written two articles and an essay for Circuit Cellar, runs Electronic System Design, a website set up to promote easy to use and inexpensive development kits. Click here to read his essay “The Future of Open-Source Hardware for Medical Devices.”