Capacitors Blog

This capacitor is used when a higher tolerance is necessary than polyester capacitors offer. Polypropylene film is used for the dielectric. It is said that there is almost no change of capacitance in these devices if they are used with frequencies of 100KHz or less.

The pictured capacitors have a tolerance of ±1%.

From the left in the photograph
Capacitance: 0.01 µF (printed with 103F)
[the width 7mm, the height 7mm, the thickness 3mm]
Capacitance: 0.022 µF (printed with 223F)
[the width 7mm, the height 10mm, the thickness 4mm]
Capacitance: 0.1 µF (printed with 104F)
[the width 9mm, the height 11mm, the thickness 5mm]

• This is a "Super Capacitor," which is quite a wonder.
• The capacitance is 0.47 F (470,000 µF).
• I have not used this capacitor in an actual circuit.

Care must be taken when using a capacitor with such a large capacitance in power supply circuits, etc. The rectifier in the circuit can be destroyed by a huge rush of current when the capacitor is empty. For a brief moment, the capacitor is more like a short circuit. A protection circuit needs to be set up.

The size is small in spite of capacitance. Physically, the diameter is 21 mm, the height is 11 mm.

Care is necessary, because these devices do have polarity.

In a way, a capacitor is a little like a battery. Although they work in completely different ways, capacitors and batteries both store electrical energy. If you have read How Batteries Work, then you know that a battery has two terminals. Inside the battery, chemical reactions produce electrons on one terminal and absorb electrons on the other terminal. A capacitor is much simpler than a battery, as it can't produce new electrons -- it only stores them.

In this article, we'll learn exactly what a capacitor is, what it does and how it's used in electronics. We'll also look at the history of the capacitor and how several people helped shape its progress.

Inside the capacitor, the terminals connect to two metal plates separated by a non-conducting substance, or dielectric. You can easily make a capacitor from two pieces of aluminum foil and a piece of paper. It won't be a particularly good capacitor in terms of its storage capacity, but it will work.

• The capacitor's function is to store electricity, or electrical energy.
• The capacitor also functions as a filter, passing alternating current (AC), and blocking direct current (DC).
• This symbol is used to indicate a capacitor in a circuit diagram.

The capacitor is constructed with two electrode plates facing eachother, but separated by an insulator.

When DC voltage is applied to the capacitor, an electric charge is stored on each electrode. While the capacitor is charging up, current flows. The current will stop flowing when the capacitor has fully charged.

When a circuit tester, such as an analog meter set to measure resistance, is connected to a 10 microfarad (µF) electrolytic capacitor, a current will flow, but only for a moment. You can confirm that the meter's needle moves off of zero, but returns to zero right away.

When you connect the meter's probes to the capacitor in reverse, you will note that current once again flows for a moment. Once again, when the capacitor has fully charged, the current stops flowing. So the capacitor can be used as a filter that blocks DC current. (A "DC cut" filter.)

However, in the case of alternating current, the current will be allowed to pass. Alternating current is similar to repeatedly switching the test meter's probes back and forth on the capacitor. Current flows every time the probes are switched.

Tantalum bead capacitors are polarised and have low voltage ratings like electrolytic capacitors. They are expensive but very small, so they are used where a large capacitance is needed in a small size.

Modern tantalum bead capacitors are printed with their capacitance, voltage and polarity in full. However older ones use a colour-code system which has two stripes (for the two digits) and a spot of colour for the number of zeros to give the value in µF. The standard colour code is used, but for the spot, grey is used to mean × 0.01 and white means × 0.1 so that values of less than 10µF can be shown. A third colour stripe near the leads shows the voltage (yellow 6.3V, black 10V, green 16V, blue 20V, grey 25V, white 30V, pink 35V). The positive (+) lead is to the right when the spot is facing you: 'when the spot is in sight, the positive is to the right'. 

• For example:   blue, grey, black spot   means 68µF
• For example:   blue, grey, white spot   means 6.8µF
• For example:   blue, grey, grey spot   means 0.68µF

In many ways capacitors are the hidden saving grace of the electronics world. They play an essential role in smoothing switch transitions by storing and releasing a small amount of energy over short time scales. Although inductors can play the same role, I think it is safe to say that without small, accurately valued capacitors the modern electronics industry would be a very different beast. Essentially, capacitors store charge, which means that the amount of charge they can store is related to the area available to put said charges. Over recent years, the development of better control over small scale structuring has lead to large increases in capacitance in relatively small packages. The increases have been such that there have been some thoughts of putting these supercapacitors to work as battery replacements in applications where high currents are required.

Advanced Capacitors World Summit 2009Final program confirmed featuring the latest in industry developments, applications and technology

PORTLAND, Maine, January 6, 2009 —IntetechPira, a leading conference and research organization is pleased to announce the final program for the 7th annual Advanced Capacitors World Summit 2009 set for March 31 – April 2, 2009 at the Hilton Torrey Pines in La Jolla, CA, US.

Co-Chaired by Richard Smith, ANA Strategic System Group and Andrew Burke of the University of California Davis Institute of Transportation Studies, this year’s program is designed to help current and prospective users, integrators and suppliers of advanced power systems understand modern energy storage and delivery challenges for power intensive applications and identify business opportunities and realities with adopting advanced capacitors and capacitor hybrid systems to solve application energy requirements. Speakers will discuss the latest market trends and developments, power engineering and integration strategies, design and business implications and costs associated with advanced power systems for various applications, including transportation, automotive, power and consumer electronics and renewable energy.

Market Overview and industry developments:

Bobby Maher of M Cubed Consulting will start off the program with a comprehensive overview of ultracapacitor market trends and technology advancement and David Alexander from IVUS Energy Solutions, creator of the patented FlashPoint Power Technology, will address serious challenges that arise when developing capacitors for the market. Andy Burke of UC Davis will provide an engaging comparison of ultracapacitors and advanced battery technology in terms of performance, cost and versatility, while John Miller of Maxwell Technologies will show how the two technologies can be best applied in tandem. A panel presentation from members of the investment community will conclude the morning session and will provide insight on how to secure funding in uncertain economic times.

John Skibinski of Eaton Corporation will shed light on the growing demand for advanced energy storage technologies for wind and solar applications. Speakers from Volvo Technology Corporation, General Electric and NREL will discuss engineering energy storage systems for hybrid electric vehicles and heavy hybrids. Aerospace applications will be explored with presentations from Lockheed Martin Aeronautics and company partner PC Krause and Associates and additional new and emerging applications will be covered by Jin Song of Nesscap.

Olgierd Paluskinski of the University of Arizona and M Grant Norton of GoNano Technologies will discuss the latest work with improving the energy density of capacitors. Paluskinski will also discuss how his group has used nanotechnology to achieve better performance and reduced cost for photovoltaics applications serving to reduce fluctuations in output power while increasing conversion efficiency. Yuri Maletin of APowerCap Technologies will reveal how nano-engineered capacitors using inexpensive nanoporous carbon material can lead to improved performance, while reducing cost, in automotive, hand-tools, energy quality and power management applications and systems.

Applications and technology:

Additional presentations from ISE Corporation, Ionix Power Systems LLC, Sigma Technologies International, Rockport Capital and Battery Ventures will also be featured.

As one of the worlds leading forums for discussing the latest technical advances and market trends in the EC industry, IntertechPira’s Advanced Capacitors World Summit 2009 is a dynamic industry event, providing a unique opportunity to gain the necessary knowledge and network with global leaders from around the world.

For complete program details and registering options, please visit: www.advancedcapacitorsws.com

Members of the press interested in attending, to find out if you qualify for a complimentary press pass, please contact Press Officer Sheri Bonnell at sheri.bonnell@pira-international.com or +1 207 781 9637.

 Recent advances in electrochemical capacitors for energy storage open new opportunities for water desalination devices with high energy efficiency.

Existing technologies for hard, brackish and sea water desalination are highly energy consuming even in the case of the best available technology nowadays, Reverse Osmosis. In addition to this problem, the construction of desalination plants requires intensive capital expenditures.

Capacitive Deionization is a technological alternative to Reverse Osmosis provided it is a non-membrane and low-pressure process, which are possibly the two main drawbacks of the Reverse Osmosis technology. The Capacitive Deionization concept is schematically represented in the Figure. During the deionization cycle, an external electrical charge is applied on a pair of electrodes introduced in the feed water, this makes the ions dissolved in the water to migrate towards the electrode of opposite charge, where they are adsorbed. In the regeneration cycle, the electrical load of the electrodes is switched off, therefore adsorbed ions are released. If an electrical circuit is connected at this stage, an electrical current will be produced, just like in the discharge of a capacitor.

Early studies almost 40 years ago showed that Capacitive Deionization could be a feasible technology for low-cost water desalination, but by that time appropriate materials were not available yet. However, nowadays with the most recent advances in electrochemical capacitors, there are improved electrodes with performances good enough to bring the Capacitive Deionization systems from research laboratories to real life applications.