## Electrical Fundamentals

A typical AA battery (a rechargeable NiMH one)

Since much of the subject matter relating to fan controllers requires a basic understanding of electrical power, I thought it might be edifying to review some of the basic concepts of electricity.

Electric charge is a property of subatomic particles (most notably, the proton [+] and electron [-]). The presence of a charge gives rise to the electromagnetic force, one of the four fundamental forces in nature. The amount of charge is usually expressed in coulombs. Voltage is the electrical potential difference between two points, or the difference in electrical potential energy between two points. This is measured in joules per coulomb, or volts. Measuring voltage requires connecting the two leads of a voltmeter (positive and negative leads) to the two points across which voltage is to be measured. This, to measure the voltage of a battery, one lead is connected to the positive terminal of the battery and the other lead is connected to the negative terminal. A common use of the term voltage is in describing the voltage dropped across an electrical device (such as a resistor). The voltage drop across the device can be understood as the difference between measurements at each terminal of the device with repsect to a common reference point or ground. The voltage drop is the difference between the two readings. Two points connected by a conductor without resistances and not within a changing magnetic field have a voltage of zero. The conventional symbol for voltage is V.

A typical digital multimeter, which can be used to measure voltage and current.

A second important concept is current, the flow of electric charge. Electric charge flows when there is a voltage preent across a current. It is measured in coulombs per second, or amperes. Electrical conductance is the ease at which an electrical current passes. There are two primary forms of current: direct current (DC), the unidirectional flow of electric charge (usually found in batteries, thermocouples and solar cells), and alternating current (AC), in which the movement of electric charge periodically reverses direction (the form of power usually delivered to businesses and residences). The conventional symbol for current is I.

If there is electrical conductance, then there must also be an inverse quantity: electrical resistance, the opposition to the passage of electric current, which is measured in ohms. The key relation between voltage, current, and resistance was discovered by Georg Ohm in 1827 and is expressed as Ohm’s Law:

V = I * R

or voltage equals current times resistance. Thus the current between two points is directly proportional to the potential difference across the two points (and inversely proportional to the resistance). Although this relationship seems somewhat obvious, the discovery of Ohm’s law was a major development in the history of electronics.

A typical 470-ohm resistor.

When electrical charges move through a circuit where there is an electric potential difference, the potential does work on the charges, converting the energy into kinetic energy. The unit of power in physics is joules per second (J/s), or watts. The conventional symbol for power is P. You may have guessed already that power between two points in a circuit can be measured by multiplying current in amps (coulombs/sec) by the voltage in volts (joules/coulomb), which leaves us with joules per second (power in watts). Thus:

P = V * I

This is known as Joule’s Law, which gives us a measure of the dissipated power between two points in a circuit. By combined Ohm’s Law with Joule’s Law, we can obtain an alternate way of expressing the dissipated power:

P = (I * R) * I = I^2 * R

These basic equations give us enough information to do some quick-and-dirty calculations with fan controllers. Assume that we have 4 fans to control, and each fan uses half an amp (.5 A) The total current used by the fans is thus .5 A * 4, or 2 amps. Let us also assume there is a 4-channel, 45-watt fan controller available. Using Joule’s Law,

p = V * I, or I = P/V

Thus, we can calculate how much current the controller can handle by dividing the power by voltage. Since the controller is 45 watts, and each fan uses 12 volts of DC power, I = (45 W/12 V) = 3.75 A. Therefore, the controller has more than enough power to handle the 4 fans.

An electric circuit is an interconnection of electrical components such that an electric charge is made to flow along a closed path, usually to perform a useful task. COmponents can include resistors, capacitors, switches, transistors and transformers, but for purposes of this introductory article, I will focus on the resistor. The resistor is a passive element (it consumes and does not produce energy), and, as the name suggests, it resists the current through it, dissipating its energy as heat. The resistance is a consequence of the motion of charge through a conductor. The resistance of most materials is relatively constant over a range of temperatures and currents; materials is relatively constant over a range of temperatures and currents; materials under these conditions are known as “ohmic”. In a fan controller, resistors will often be used to reduce the voltage to a fan; however, since the resistor dissipates energy as heat, the buildup of heat is often a concern.

I may write a follow-up article to further explain electronic components, but this should be enough basic concepts for the uninitiated reader to understand the fundamentals of fan controllers. Any feedback on this article would be greatly appreciated.

## Review: Lamptron FC-2

Front panel of the Lamptron FC-2

For those users who put power at a premium, the FC-2 may be the ideal solution. In an era when some fan controllers offer a mere 7 watts per channel, the FC-2 boasts a whopping 45 watts per channel, with a total of 6 channels. It is available in both black anodized aluminum, as well as plain aluminum. The aluminum is CNC milled, which should please those who put a premium on aesthetics.

The FC-2 fits into a 5.25-inch drive bay, and requires up to 3 Molex connectors to power it (it is advisable to connect all 3 connectors to the power supply to prevent a current overload, but the controller will work with only one connector connected). It comes with fan extension wires for all 6 channels (all fan connectors are 3-pin), as well as screws for mounting. The power cable is pre-attached to the fan controller (likely due to the FC-2’s power cable having a higher-gauge wire to handle the increased power load).

The PCB on the FC-2 has been simplified considerably in comparison with its predecessors. Lamptron used a pulse-width modulation (PWM) design for the controller, rather than using a resistor-based design, which makes it somewhat more efficient than a resistor-based system which would dump additional voltage as heat.

Another view of the Lamptron FC-2, showing the Molex power connectors

It should be noted that when the fans are in the off position, it is an absolute off, unlike some controllers which consistently supply some power to allow the fan to spin at a slow speed. This is useful if you want to isolate the source of noise in a PC, but not so useful if you forget the fans are not running and end up damaging a component. The LED brightness increases as the fan speed increases; thus the LEDs will be brightest when the fan speed is at a maximum. This can be handy to users who want to know the fan speed right away by just looking at the LED brightness.

The controller itself seems to work solidly; it can handle several fans running at maximum speed without struggling.

On the whole, the Lamptron FC-2 does everything the user would expect of it and more. It lacks some of the features of the more expensive fan controllers (it is, after all, only a manual fan controller), but with a whopping 45 watts per channel, it should be powerful enough for just about everybody, and with a retail price of about \$40, it offers good value.

Specifications:
Dimensions: 5.25″ Bay
Max Power: Up to 45W per channel
Colors Available: Black Anodized Aluminum, Plain Aluminum Finish
DC Input: 12V(Standard 4 Pin Molex Connector)
LED Indicator: 12 Blue LEDs 5.0V
Fan Connectors: 6
Fan RPM Knobs: 6

Features:
CNC Milled from blocks of 3/4″ Thick Solid Aluminum
Normal Output 45 W Each Channel
Six 3-pin Fan Connections on Backside
LED Brightness is Controlled by RPM Knob

## Loud Fans, Power Reduction, and Other Reasons to Add Fan Control to a PC

The Lamptron FC-Touch, just one of many commercially available multi-channel fan controllers which can eliminate loud fans and help reduce power consumption.

The hardcore gamer or computer hardware enthusiast likely does not need to be convinced that having some method of fan control is a good idea. The user who has already spent hundreds of dollars or even more on a high-end PC, a graphics card with a powerful GPU, and possibly several other pricey peripherals will likely see adding a fan controller as a wise investment, especially since high-performance systems often incorporate loud fans. The average desktop user may not think having a fan controller is necessary, and they may be correct. For them, running the fan at maximum speed whenever the computer is on will provide a reliable method of cooling the system. Moreover, some fans have a lifespan of 60,000 hours, or almost 7 years of continuous use, thereby virtually guaranteeing that the fan will be one of the last computer components to fail, and seemingly giving the typical PC owner little justification for adding fan control.

Nonetheless, there are several advantages to  adding fan control to a PC. Although each user might have different reasons for wanting to control the fans, the following come to mind as the most likely justifications:

### [1] Loud fans.

Modern PCs are a vast improvement over earlier ones in terms of noise output.  Anyone who had an XT or any of the other early PCs can likely attest to this; while loud fans are sometimes an issue, the fans generally are not as noisy as they once were. Still, as a fan runs faster, the noise generated by that fan increases exponentially. Since fan noise increases with the fifth power of the fan speed, reducing rotations per minute (RPM) by even a small amount potentially means a reduction in fan noise. Additional fans on a PC can increase the decibel level of the computer to as much as 70 dB. And loud fans are no fun.

### [2]  Power consumption reduction.

While eliminating loud fans is enough of an incentive for many users to invest in a fan controller, the efficiency argument should be considered as well. Circuits consume electrical power; chips and transistors need power to operate, while components such as resistors will dissipate heat, which means more energy loss. Modern controllers can be made with low power consumption chips. For example, if we have a PWM controller operating at 5 volts (V) and drawing 30 milliamps (mA), we can calculate the amount of power consumed:

P = V*I = 5 V * 0.030 A = 0.150 Watts (or 150 mW)

In this example, we are using Joule’s First Law (power in watts = voltage in volts * current in amps, or P = V*I) to calculate the power.  That is 150 mW (milliwatt)  for the fan controller. A 300mA typical fan operating at 120 volts consumes this much:

P = V*I = 120 V * 0.300 A = 36 Watts

A fan controller would enable the user to control the voltage sent to the fan.  Assuming that the user runs the fan with half the voltage, the power consumption of the fan will be reduced in proportion to the voltage reduction:

P = V*I = 60 V * 0.300 A = 18 Watts (or 1800 mW)

The system will consume 150 mW of power that would not have been used if the system did not have a fan controller at all, but the fan is now consuming 1800 mW less than it was before. Thus, the net savings in power consumption is 1650 mW. Moreover, since most fan controllers can control multiple fans, the user can save even more power by reducing the voltage to several fans, while the power consumed by the controller remains the same, meaning that the more fans the system uses, the greater the potential power savings.

### [3] Improved fan reliability.

All PC fans have bearings, and these bearings generate friction, which in turn will slowly wear the bearings, which in turn will lead to the end of the fan’s life span. By rotating the fan slower, the friction and the heat generated by the fan will be reduced, increasing the lifetime and overall reliability of the fan. This alone might recoup the cost of buying a PC fan controller.

### [4] Dust accumulation reduction.

The air carries dust. Filters reduce the dust, but even with these filters, dust will get into your PC. This causes two problems: [a] it clogs up the filter and reduces the amount of air that goes ito the box; [b] dust sticks to the surfaces of chips and heat sinks, reducing their ability to disappate heat effectively and increasing the temperature inside the box. If the incoming air volume is reduced to the required volume for reducing the speed of the fan, less dust will be pushed through the filters into the PC.

### [5] Aesthetics.

While the first four items on my list are the ones usually cited as the most common reasons for utilizing some form of fan control, it should also be noted that many of the newer fan controllers have been designed as much with an eye towards having an aesthetically-pleasing look as they are to work efficiently (the Lamptron FC-Touch pictured above is just one such example). Many of them have a means of changing the color of the LED outputs, and almost all of them except perhaps the most primitive ones have something to offer visually. Any user who is looking for an add-on that enhances the looks of the system (while potentially offering substantial benefits in the form of power and minimizing noise from loud fans) should consider adding a fan controller.

### Conclusion

While there are many reasons one might want to install a fan controller, the most compelling reasons, in my opinion, is the potential for savings in power consumption and to eliminate the issue of loud fans.  If loud fans are the main reason you are considering installing a fan controller, you probably want to explore other options first.  If you are running an old system, clean all the fans and see if this resolves the issue. If you can isolate the noise to a single loud fan, consider replacing the fan. But keep in mind that even a perfectly good fan will get louder as it runs faster. If other options have been exhausted and you still have an issue with loud fans, it is probably time to consider a fan controller.