Electronics DIY published a new build, the Curious C-beeper:
Curious C-Beeper is a fun to build little probe that can be used to quickly detect the capacity of capacitors in pF nF range, test their stability with temperature changes, find broken wires, locate wires, trace wires on PCBs, and to locate live wires behind the walls without touching them. The circuit uses three transistors to make a most unusual capacitance beeper probe. When a capacitor is touched to the probe, the probe beeps at a frequency that varies with capacitance. The frequency change is so steep with capacitance that tiny capacitors may be precisely matched or an exact fixed value may be selected to replace a trimmer in a prototype.
Curious C-beeper - [Link]
Rechargeable batteries save us a lot of money but take a lot of time. What if you could recharge a battery in seconds instead of hours?
Rechargeable batteries save us a lot of money these days but for the savings, we give up some of our time, waiting for them to recharge. What if though. What if there was a rechargeable battery that took seconds to recharge instead of hours? That is exactly what I’ve invented and I need your help to bring this to the masses and show the world that we no longer need to waste hours of or lives waiting for a battery to charge.
With the leaps and bounds being made today with capacitors, they’ve gone from being able to store a tiny potential of energy to now, being able to store enough energy to be considered a power source. These high Farad capacitors are known as super capacitors and aside from providing electricity for an extended period of time, they can also be charged very quickly. Recently, there’s been another development, combining the technology of super capacitors with lithium ion batteries. The usually downside to super capacitors from batteries is that they don’t provide electricity for nearly as long. However, with the advent of the lithium ion capacitor, that is quickly changing.
30 Second Charging, Rechargeable Battery - [Link]
Dave explains, shows, and measures a potentially big trap with using high value ceramic capacitors. Is your 10uF capacitor really 10uF in your circuit? You might be shocked! Those humble X7R caps you think are a “stable” dielectric? think again… Class II and above ceramic capacitors can vary their capacitance drastically with DC bias voltage level and also the applied AC voltage.
EEVblog #626 – Ceramic Capacitor Voltage Dependency - [Link]
Capacitors may seem simple enough, but specifying them has actually grown more complex in recent years. The reason why comes down to freedom of choice. The universe of capacitors has expanded greatly over the past few years, in large part because of capacitor designs that take advantage of advances in conductive polymers.
These advanced capacitors sometimes use conductive polymers to form the entire electrolyte; or the conductive polymers can be used in conjunction with a liquid electrolyte in a design known as a hybrid capacitor. Either way, these polymer-based capacitors offer a performance edge over conventional electrolytic and ceramic capacitors. [...]
The various polymer and hybrid capacitors have distinct sweet spots in terms of their ideal voltages, frequency characteristics, environmental conditions, and other application requirements. In this article, we will show you how to identify the best uses for each type of advanced capacitor. We will also highlight specific applications in which a polymer or hybrid capacitor will outperform traditional electrolytic or ceramic capacitors.
Understanding Polymer and Hybrid Capacitors - [Link]
This video discusses how to measure the ESR (equivalent series resistance) of a capacitor using an oscilloscope and function generator. All of the capacitors tested in this video were 220uF electrolytic caps. In reality, the resistance in the plates of a dried out electrolytic capacitor can’t be modeled as a simple series resistor, but for the purposes of identifying good from bad, this simplification works fine.
Measure Capacitor ESR with an Oscilloscope and Function Generator - [Link]
Rupert Hirst writes:
I finally got round to making my capacitor ESR tester this week after finding a nice simple 5 transistor version by EEVBlog member Jay_Diddy_B. Unfortunately, for me, the design was only SMD so, I decided to replicate his schematic in Eagle PCB using a through hole component design.
Dr Brown’s capacitor ESR tester - [Link]
This Design Idea describes a simple two-chip CMOS circuit that can sort capacitors into 20 bins over a wide range (100pF to 1μF), using 10 LEDs to display the value range. The circuit is power efficient and can be run using two CR2032 cells. As such, it can be built into a handheld probe. by Raju Baddi
Simple capacitance meter bins parts - [Link]
Electro Labs has posted a detailed tutorial on why and how to use bypass capacitors:
You may have heard about the phenomenon of bypassing in circuits, however, we may not have sufficient knowledge of how to apply this technique in real circuits. In this tutorial, we will discuss about the bypass capacitors, why we need to use and how to use these capacitors in circuits.
Bypass Capacitors – Why and How to Use Them? - [Link]
Here is an app note from NXP on capacitor bypassing.
Bypass capacitors are applied between the power supply pins VCC and GND of integrated circuits. They reduce both the power supply noise and the effect of spikes on the supply line. They also provide instantaneous current demands of the integrated circuit as it switches. This application note describes the different properties of bypass capacitors and provides a guide to their use.
Properties and application of bypass capacitors - [Link]
The decoupling capacitor…is it really necessary? Art Kay writes:
Before working as an applications engineer, I worked as an IC test development engineer here at TI. One of my projects was to characterize an I2C temperature sensor. After writing some software, I threw together a hand-wired prototype board. I was in a hurry, so I left off that pesky decoupling capacitor. Who needs it, right?
I collected data for about a week, and none of my results matched expectations. I made numerous changes in an attempt to improve performance, but nothing worked. Finally, I decided to add the decoupling capacitor. As you might expect, this solved the issue.
The decoupling capacitor…is it really necessary? - [Link]