West Florida Components

What Are Peltier Cells and How Do They Work?

If you join two dissimilar metals by two separate junctions, and maintain the two junctions at different temperatures, a small voltage develops between the two metals. Conversely, if a voltage is applied to the two metals, allowing a current to pass through them in a certain direction, their junctions develop a temperature difference. The former is called the Seebeck effect and the latter is the Peltier effect.

Many such dissimilar metal junctions are grouped together to form a Peltier cell. Initially, copper and bismuth were the two dissimilar metals used to form the junctions. However, more efficient semi-conductor materials are used in the modern Peltier cell. These are sandwiched between two ceramic plates and the junctions are encased in silicon.

Just as you could pass electric current through a Peltier cell to make one of its surfaces hot and the other cool, so could you place a Peltier cell in between two surfaces with a temperature difference to generate electricity. In fact, BMW places them around the exhaust of their cars to reclaim some electricity from the temperature difference between the hot gases emanating from the car and the atmosphere.

Another place where Peltier cells are put to use is the picnic basket. It connects to the car battery and has two compartments – one to keep food hot and the other to keep food and drinks cool. Unfortunately, Peltier cells are notoriously inefficient, since all they do is move heat from their cold side to the hot. Part of their efficiency is also dependent on how fast heat is removed from their hot side. Usually, Peltier cells are able to maintain a maximum temperature difference of 40°C between their hot and cold sides.

Active heat sinks use Peltier cells to keep CPUs cool inside heavy-duty computers. These CPUs pack a lot of electronics inside their tiny bodies and generate huge amounts of heat when working at high frequencies of a few Giga-hertz. Peltier cells help to remove the heat from the CPU and keep the temperature constant. One advantage in using Peltier cells for this work is the CPU can regulate the amount of heat removed. The CPU in a computer has temperature sensors inside and when it senses its temperature is going up, it pumps in more current into the Peltier to increase the heat removal.

What does the Peltier do with the heat it has acquired from the hot source? To maintain its functioning, the Peltier has to transfer this heat to the material surrounding its hot surface. Usually, this is an Aluminum or Copper heat sink, which then transfers the heat to the atmosphere.

Active heat sinks that are more exotic use heat-conducting fluids to transfer the heat away from the hot side of the Peltier cell. These are specially formulated fluids with high thermal conductivity running in pipes over the hot surface of the Peltier. As the Peltier gets hot, the fluid takes away the heat and changes to a liquid of a lower density. Convection currents are set up, causing the hot liquid to move away to be replaced by cooler liquid, aiding heat transfer. Heat from the hot liquid is removed in a heat exchanger in a different part of the computer.

Parents are concerned over the type of programs their children watch on the television and would like to exercise their control. They do not want their children watching programs with excessive violence or sexual content. Since it is not possible to be always present when the children are watching TV, it is best to have a device automatically detecting the type of program coming through, and blocking it if it is objectionable.

All television sets made and sold in the US after 1999 have a special electronic chip built in and this is the V-chip. This allows parents to select the level of violent programs, which children can watch in the home. This also means that all TV programs contain a rating transmitted along with the program, which the V-chip can detect.

The FCC defines the ratings as -

TV-Y – Suitable for all children, with no violence and no sexual content
TV-Y7 – Suitable for children aged seven and over
TV-G – Suitable for general audiences, with no violence, no sex and inappropriate language
TV-PG – Parents to exercise their own discretion
TV-14 – Suitable for children above 14 only, with some violence and sex
TV-MA – Suitable for mature audiences only and may contain sexual situations and/or graphic violence

A parent can program the V-chip with a specific rating, and the chip will block all programs or shows above that rating. For example, if you have programmed a V-chip for a TV-G rating, it will allow all programs with a rating of TV-G, TV-Y7 and TV-Y, and will block all the rest.

All television programs transmit synchronizing signals, which allow a proper build-up of the picture on the screen. The electron beam painting the picture on the screen starts to sweep from the top left corner to the right edge of the screen, turns itself off, retraces itself to the left edge and sweeps again to the right edge, moving down a tiny bit in the process, until it has covered the entire height of the screen. The beam then returns from the bottom right hand corner of the screen to the top left hand corner and the whole process repeats. The vertical and horizontal retrace signals transmitted along with the TV program control all this.

As the signal returns from the bottom of the screen to the top, it follows a number of horizontal retrace lines. The twenty-first line of the horizontal retraces has data embedded in it as specified by the XDS standard. This includes captioning information, time of the day, ratings information and many others.

The V-chip is capable of reading this line 21 data, extracts the rating’s information and compares it with the parent’s allowed rating. Accordingly, the chip lets the signal pass through or blocks it.

The V-chip in the television works in conjunction with the cable box and/or the VCR. You can either utilize the V-chip or turn it off.

Batteries power most of our mobile gadgets. These are small chemical powerhouses, which generate electricity by the chemical reaction within the battery housing. Although there are different types of batteries available, all batteries contain cells that have two electrodes and a chemical or an electrolyte between them. Various combinations of series and parallel connections of the electrodes make up a certain voltage rating for the battery. For ease of understanding, we will treat the battery as made up of a single cell.

One of the electrodes is the cathode or the positive (+) terminal and the other is an anode or the negative (-) terminal. Because of the reaction between the two electrodes and the electrolyte inside, there is a buildup of electrons at the anode and a corresponding lack of electrons at the cathode. Although this is an unstable condition, and the electrons want to distribute themselves evenly between the electrodes, they cannot do so because of the presence of the electrolyte and its reaction with the electrodes. An isolated battery soon reaches a chemical equilibrium, and no further reaction occurs.

If the electrons find an alternate path to travel from the anode to the cathode, they will redistribute themselves and the number of electrons will gradually reduce, forcing the chemical reaction to start over again and create more electrons. This process continues until an inert layer covers one or both the electrodes. Usually, the alternate path is through a metal wire, which is a good conductor of electricity and links the two electrodes of the battery through a load or the mobile gadget requiring power.

Electrons flowing from the anode of the battery through the external wire to the load and back to the battery cathode constitute an electric current. Since it is usual to consider the direction of current flow as opposite to that of electron flow, we commonly say current flows from the cathode of the battery through the load and back to the battery’s anode.

Since the physical size of the battery restricts the quantity of chemical inside it, the current produced by the battery is also limited. The battery specification, as mAH or AH, is the product of the current and the number of hours the battery can produce this current continuously. In general, once the chemical within the battery has depleted itself or inert material has covered up the electrodes, the battery becomes useless. However, it is possible to revive or recharge certain types of batteries. These are the rechargeable batteries.

Once a rechargeable battery depletes itself, you can charge it up again by sending a current through it in a direction reverse to what it normally produces when connected to a load. This reverses the chemical reaction inside, and the electrolyte and the electrodes return to their initial condition. You can repeat this discharging and recharging process many times, until the electrolyte exhausts itself totally, and no further revival is possible.

For those just starting out learning about electronic components (specifically capacitors and capacitance), we know that there can be some confusion related to this topic.

In short, the answer is yes — mFd is the same as uF- which is also the same as the symbol ‘µ’ as seen in ‘µF’.

Technically ‘mfd’ represents ‘milliFarad’ while ‘uF’ stands for ‘microFarad’ which is an order of magnitude smaller. Here is where the confusion begins. Some older capacitor manufacturers used ‘mF’ in place of uF on their capacitors. Whether it was because their machines could not imprint the correct symbol ‘µ’ or for another reason not known to us, this was the common practice.

Nowadays, we see about 25% of the capacitors that come into our warehouse marked as mFd but we RARELY have any that are truly milliFarads.

On our site, we refer to microfarad as ‘uF’ to keep consistent and to make it easier for customers to find the capacitors they need. In the end. there is really no right or wrong – some other sites might use mF or mFd.

If you need more information about capacitance, check out our handy capacitance conversion chart which will help you convert microfarads into picofarads and nanofarads.

Today’s animated Google Doodle celebrates Heinrich Rudolf Hertz, the German physicist on what would have been his 155th birthday. His experiments with electromagnetic waves led to the creation of the wireless telegraph and the radio. Hertz showed that electricity can be transmitted via electromagnetic waves.

You may wonder why his last name sounds so familiar. That is because Hertz’s name later became the term used for radio and electrical frequencies. Think of hertz (Hz), kilohertz (kHz) and megahertz (MHz). In 1933, long after his death, the Hertz officially became part of the metric system.

Google’s animated doodle is an homage to Hertz’s contributions to physics. The wavy animation, which is in Google’s trademark colors of red, blue, yellow and green, is in recognition of the German physicist’s work with electromagnetic waves. Very fitting!

Robert Noyce is being honored by Google for his contributions to the electronic components industry on what would have been his 84th birthday. To commemorate his birthday, Google’s homepage has a doodle which etches the Google logo onto a microchip, a technology that Noyce is credited with co-inventing.

Known as the Mayor of Silicon Valley, Robert Noyce was the co-founder of Fairchild Semiconductor and Intel and is credited along with Jack Kilby with the invention of the integrated circuit. He earned his nickname for the work he did as a mentor to youths aspiring to succeed in Silicon Valley and in fact was a mentor to Apple founder, Steve Jobs. Jobs was one of many Silicon Valley entrepreneurs mentored by Noyce.

The holder of 15 patents related to the electronic components industry, Noyce was a major contributor to the industry and it is fitting that Google chose to honor him and his achievements.

We hope you’re going to be just as excited as we are! West Florida Components is now carrying a line of solder guns and irons! You can choose from a battery operated 15W solder iron  (perfect for marine repairs on in the field projects) all the way up to a 150W dual heat full featured gun. All the electric soldering irons and guns are proudly made in the USA by Wall Lenk Corporation and they are guaranteed for 5 full years.

All of the soldering equipment can be used for a wide range of projects, from electronics to lawn and garden equipment….and cutting and smoothing jobs like leather and wood burning.

Most of the guns and irons in stock are ‘kits’ – that is, they come with multiple solder tips and a supply of rosin core solder to get you started on your soldering projects. Are you just learning how to solder? Check out our guide on the basics of “How to Solder” which gives plenty of pointers for soldering newbies.

MOS-FET, which is an abbreviation of Metal-Oxide-Semiconductor Field Effect Transistor, is a very important kind of transistor. Many IC’s are constructed of arrays of MOS-FETS on a tiny sliver of silicon.

They are very small, easy to manufacture and many MOS-FETS consume a small amount of power making them an excellent choice for many applications.

It is the most common type of transistor available for either digital or analog circuits, replacing the bipolar transistor which was much more common in the past.

The word ‘metal’ in the name is actually now a misnomer because what was originally the gate material (often Aluminum) is now more often a layer of polysilicon (aka polycrystalline silicon).

Some of the most common questions we get are about Schottky diodes.

The simple definition of a Schottky diode is a diode with a very fast switching action as well as a lower forward voltage drop.

As the current flows through a diode, it experiences a slight voltage drop across the diode terminals. Normally, a diode has approximately 0.7-1.7V drops. A Schottky diode, however, will see a drop in voltage between 0.15-0.45V. The benefit of this lower drop? A much higher system efficiency.

The construction of a Schottky diode also effects the voltage drop and switching time. A Schottky diode has a metal semiconductor junction as the Schottky barrier rather than the traditional semiconductor to semiconductor junction seen in conventional diodes. It is this barrier that affects the voltage drop and the speed of the switching times.

Sometimes Schottky diodes are misspelled by adding an ‘e’ to the end: Schottkey. The correct spelling is Schottky which is the surname of the man that is credited with putting these electronic components in the history books.

Semiconductor Markings – Available Methods

Traditionally, most components have two or three lines of identifying marks plus a company logo. Over time, the manufacturer codes have become more involved to incorporate a component’s identification plus the complete history of the process. Early on, it was the military applications that required very specific markings and identification processes. Current package markings are a by-product of those military requirements.

When a semiconductor is clearly identified, there is less room for error in the production process. Reducing errors when a component is in use for production saves time. There is also less product waste and the production process becomes more streamlined.

As the size of electronic components has decreased, the available space that manufacturers have to mark each piece has also decreased. The technology required to complete this task has become increasingly more complex.

The chief reason for the more complex codes stems from the demands of the end users. They need to have complete traceability of the product; from the history of the production cycle including the date and location of manufacture to the exact lot code. Possession of this information is critical to the end user in the event of a recall or defective components.

There are four primary methods to marking components in current use. Use of the various methods depend on the size, the type and the environment of the component production.

The methods are:
-Ink marking
-Electrolytic marking
-Pad printing
-Laser marking

In ink marking, inkjet printers are used. The technology is called ‘drop-on-demand’ which means that the flow of ink is controlled to create a pattern of ink droplets to form an image marking.

Electrolytic marking employs low voltage electric current with a stencil. The top layer of the package is etched by electricity flowing from the marking head, assisted by an electrolyte chemical. The process takes approximately 2-3 seconds to complete.

Pad printing is the most traditional of all the processes. A steel plate is etched with the image of the imprint. The ink is transferred to the plate which then is applied with pressure to the surface of the electronic component.

Laser marking is the most recent development in the marking process. It provides the greatest flexibility in the size, timing and complexity of the markings. The laser process is also the fastest method to mark electronic components; it is not uncommon for this process to print up to 300 characters per second. An additional benefit of using laser printing is the ability to produce a clean mark on many irregular surfaces.

No matter which method has been used to mark the semiconductors you use, you can be sure that much thought has been put into the decision.