In this approach, the voltage applied to the fan is always either zero or full-scale—avoiding the problems experienced in linear control at lower voltages. Follow these steps to control the fan speed using HWiNFo. If it is not set, the old fan control … So from an acoustic perspective, on/off control is far from optimal. Reducing the external component count, this approach makes the external circuit much simpler. I'm not too handy when it comes to electrical stuff, any suggestions on what kind of dimmer switch? On/off control: The next simplest method of fan control is thermostatic, or on/off control. fan diameter, all in a compact, lightweight, energy-efficient design. The tach signal indicates whether the fan is running and its rate of speed. Cookies help us deliver our Services. The external circuit required is also relatively expensive. A 3-wire fan can be controlled using the same kind of drive as for 2-wire fans—variable dc or low-frequency PWM. An obvious example is the notebook PC. Remove the front grill, exposing the fan blade. I have a single speed router which spins extremely fast. You can add a resistor, a capacitor or an inductor in series with fan permanently. The Analog Devices ADM1032 is an ideal sensor for on/off fan control using a temperature setpoint. The principal advantage of this drive method is that it is simple, inexpensive, and very efficient, since the fan is either fully on or fully off. For example, a 12-V fan with a control voltage range from 7 V to 12 V could be running at half speed at 7 V. The situation is even worse with a 5-V fan. However, with only two wires, a tach signal is not readily available. running a fan slower reduces the noise it emits. This article will describe how and why this evolution has taken place and will suggest some useful approaches for the designer. However, in recent years, the technology of using these fans has evolved significantly. Step 2 - An electric cooling fan is used primarily to boost engine performance and cut down on emissions. Finally, running the fan slower also improves its lifetime, increasing system reliability. Ya think Gorilla Glue would work? That being said, I don't know what a "fan dimmer" is such as the one /u/mdedm is talking about. Multi speed motors have more than one set of windings. Why and How to Control Fan Speed for Cooling Electronic Equipment. The more common installation though is to have the power run to the ceiling fan … 5-V fans allow only a limited range of speed control, since their start-up voltage is close to their 5-V full speed level. Solid-state controls change the level … Loss of fan speeds 1, 2 and less commonly 3 usually points to the failure of the resistor pack, which is attached to the air-box. When the PWM drive is switched to the off phase, the fan’s internal tach signal-generation circuitry is also off. Sometimes I'd like to just have them spin slower. If quiet operation is a priority, look for a model that emits 35 dB or less. It seems you wish to run the fan at a constant lower speed, and would like to keep this speed for ever. To remove the fan blade, place a hand on each side of the blade and gently rock the blade from side to side, and pull the blade off. Take the back off the fan … In order to keep the power used by the ADM1028 at a minimum, it operates on supply voltages from 3.0 V to 5.5 V, with +2.5-V full scale output. Wiring a Speed Control for the Ceiling Fan Speed and Dimmer Switch for the Ceiling Fan Light. Speed control—one way to answer some of these objections to the use of a fan—can have these advantages: There are many different types of fans and ways of controlling them. The MAX6650 interfaces to fans with tachometer outputs to monitor and control fan speed. Remote control. Appliances, kitchen utensils, drills, chainsaws, and machines of all ilk. Because the tach output is typically from an open drain, it will float high when the PWM drive is off, as shown in Figure 1. Activating the Automatic Fan Speed checkbox on the main screen enables fan control. Rate controls For home use are usually either TRIAC or VFD (Variable frequency drive). They would each have their own parameters. However, these have proved insufficient in many popular consumer electronics products—and they are also somewhat expensive. Someone here is going to try to help you fix it when it's busted. Consider, for example, a 12-V fan (rated maximum voltage). Besides eliminating the need for noisy pulse stretching and the commutation noise associated with low-frequency PWM, it has a much wider control range than linear control. The typical fan speed control is different windings inside the motor - Michael is right on there. The user needs to set the conditions under which cooling is needed—typically when the temperature exceeds a preset threshold. Since the PWM drive signal is applied directly to the coils of the fan, the fan’s electronics are always powered on, and the tach signal is always available. However, in recent years, the technology of using these fans has evolved significantly. This method is also very easy to implement. Fan Control in Windows 10 With a Fan Controller . A 3-wire fan has power, ground, and a tachometric (“tach”) output, which provides a signal with frequency proportional to speed. Whether the old fan control or the new Advanced Fan Control strategy is used depends on the Advanced Fan Control checkbox on the FAN CONTROL tab of the CONFIGURE window. You don't have to settle for the three speeds of a typical ceiling fan. Keep an eye on your fan RPMs and temperatures—you should find that they react just as you set out in the Temperatures and Speeds tab. Estimated Time: Depends on personal level experience, ability to work with tools and access to the ceiling fan. Your fan will buzz, but the speed will be adjustable. A fan speed control switch makes it easy to adjust the speed at which a fan spins. By using our Services or clicking I agree, you agree to our use of cookies. The typical box fan is driven by an AC induction motor. A new … With low- frequency PWM, however, the tach signal is valid only when power is applied to the fan—that is, during the on phase of the pulse. This article will describe how and why this evolution has taken place and will suggest so… Switching the coils on and off generates some commutation noise. The typical box fan is driven by an AC induction motor. The relationship has limitations. I replaced the three way switch with a fan dimmer, connected to the highest speed. It is widely used for controlling heating elements, motors (be careful here, it only works with certain types of motor), and high-power stage lighting, just to name a few uses. This means that there is no indication as to how fast the fan is running—or indeed, if it is running at all. It would work wonders on a soldering iron to drop temp for marking plastics, speed control of a little on/off desktop fan or on a small blower for a DIY coal furnace. Fan dimmers are usually TRIAC circuits. It is more energy efficient, because the fan is always either fully on or fully off. A good alternative is active cooling, introducing a fan into the system to generate airflow around the chassis and the heat-generating components, efficiently removing heat from the system. Using a Phillips head screwdriver, remove the four screws on the outside perimeter of the front grill. The rotating assembly of blades and hub is known as an impeller, rotor, or runner.Usually, it is contained within some form of housing, or case. With the fan coils continuously switched on and off, audible noise may be present. Others also offer light-dimming and thermostatic control … Some cookies are required for secure log-ins but others are optional for functional activities. What these systems all have in common, besides significantly smaller—and still decreasing—size, is that the amount of heat they must dissipate does not decrease; often it increases! It is quieter than always-on or on/off control, since the fan can run at lower speeds—that can be varied gradually. The first law of fans is a useful tool when working out the volumetric flow rate supplied by a fan under speed control or conversely working out what the RPM would be to deliver a required volume of air and hence what frequency to set a variable speed drive (VSD) to. Worst acoustic performance—fan is always running. Cases like NZXT's H-series i versions have a built-in link box which gives you software control over your CPU fan in much the same way as Speedfan, but in a more intuitive manner. This may direct the airflow, or increase safety by preventing objects from contacting the fan blades. The main advantages of this are guaranteed fail-safe cooling and a very simple external circuit. The principal advantage of linear control is that it is quiet. Such a fan may require at least 7 V to start spinning. Download PDF. Lastly, back at the main SpeedFan window, check the “Automatic Fan Speed” box. The switch positions on both ceiling fan remote units must match. These fans are featured in both front and rear wheel drive vehicles and are activated by a coolant sensor via the computer. This feature is implemented in a number of Analog Devices fan controllers, such as the ADM1031 and the ADT7460. The disadvantage of on/off control is that it is very limited. This heat needs to be removed quietly and efficiently. Press question mark to learn the rest of the keyboard shortcuts. The commutation noise is also eliminated, or reduced significantly, since the coils are being switched with a frequency outside the audible range. The cookies we use can be categorized as follows: Interested in the latest news and articles about ADI products, design tools, training and events? A whole-house fan offers a green alternative to central or window air conditioning, especially if ocean or bay breezes in the evening cool the exterior air. You're right. The tach signal, when driven by a dc voltage, has a square-wave output closely resembling the “ideal tach” in Figure 1. running a fan slower can reduce the power it consumes. I was thinking adding some kind of resistor which reduced all the speeds in one shot, but I honestly don't even know if that would work or not. Instead of switching the power to the entire fan on and off, only the power to the drive coils is switched, making the tach information available continuously. I'm not sure about how to move the taps to the motor, but that's the right way to do it. a few tabs on the feet. My guess is that it's some sort of an SCR chopper circuit which will then be capable of very roughly changing the primary harmonic of its output. Read more about our privacy policy. 99 With the remote, you can turn the fan on and off and adjust its speed. The trend in electronics, particularly consumer electronics, is towards smaller products with enhanced combinations of features. But a dimmer switch sounds like an even better solution. Our data collection is used to improve our products and services. The way in which your fan's speed control actually works depends upon whether it has a capacitor or solid-state control. Figure 6 shows a case of pulse stretching. It is always valid, since power is continuously applied to the fan. Each set of windings are almost like a separate motor. But for large router bits the speed should be reduced to half as fast. Although these fans are relatively new to the market, they are rapidly becoming more popular. Instead of buying a new router with a speed control dial built in I got this and it does the job. Go to https://nordvpn.com/jaredowen and use code jaredowen to get 70% off a 3-year plan and an extra month for free. This form of speed control is open-loop. A disadvantage is that the tach information is chopped by the PWM drive signal, since power is not always applied to the fan. We're Here to Help. Consequently, lots of electronic components are being shoehorned into very small form factors. If you want more control over your CPU fan and other aspects of your system, a fan controller is a good bet. Box fans. Intro. Aloysius, is clever, I have seen a few of his answers,and the logic is good (and gives the ymmv, easier to trust someone that knows what they do not know, and will admit it.) How to Wire a 2 Speed Whole House Fan. Protect yourself online today! Press J to jump to the feed. We will discuss here various fan types and the advantages and disadvantages of control methods in use today. The Harbor Freight Router Speed Control is a bargain-priced (on sale for $19.99, with a 20% OFF coupon, just $17.40 with the tax) general purpose electrical controller, despite its very limited name. Some box fan packages include a remote control that allows you to operate the fan from across the room. (With the FET either off or in saturation, its dissipation is very low, eliminating the significant losses in the transistor in the linear case.) Cost about $10. Doors, walls, furniture and floors, popcorn ceilings *and* ceiling fans. PWM, in brief, uses the relative width of pulses in a train of on-off pulses to adjust the level of power applied to the motor. Although it seems to do a job similar to a dimmer and actually looks very similar, the fan speed switch is more like a regular light switch and will be wired in series with the fan. In industrial applications, we use what are called Variable Frequency Drives (VFDs) which are basically power supplies that output a 1 or 3 phase voltage similar to what you would get out of the wall, but at an almost arbitrary frequency up to several hundred Hz. The PWM signal drives the fan directly; the drive FET is integrated inside the fan. They cost about $10 Next would be a capacitor type "de-hummer" control and it gives you about 3 usable speeds, if the control & fan are matched. Hi ramarc, Thanks for the reply, my Motherboard does not use PWM for Fan control as it only has 3 Pin Headers for connections. Provide us with your email address to get Analog Dialogue delivered directly to your inbox! Make sure the fan isn't plugged into a power supply. Choose from one of our 12 newsletters that match your product area of interest, delivered monthly or quarterly to your inbox. Wipe the blade with a … It has a comparator that produces a THERM output—one that is normally high but switches low when the temperature exceeds a programmable threshold. If so it would be a very electrically noisy circuit which the motor won't really care for which would explain why the motor would like to buzz. The advantage of this programmable hysteresis is that the fan does not continually switch on/off when the temperature is close to the threshold. The fan is switched on only when cooling is needed, and it is switched off for the remainder of the time. For such machines, the speed is controlled by the line frequency and the number of poles for which the motor is wound. It is also an additional source of power consumption in the system—a very important consideration if power is to be supplied by a battery. A fan is a source of noise, however. Because of the need to overcome inertia, the voltage required to start a fan is higher than the voltage required to keep it spinning. I got me one of these...http://www.popsci.com/sites/popsci.com/files/import/2013/images/2009/10/variac_1.jpg. However, as we have noted, the speed-control range is limited. 3-Speed Box Fan combines the cooling power of 3 fan speeds with the wide-area air flow of 1820 CFM air circulation and a 20 in. low-frequency pulse-width modulation (PWM), 1995 - 2020 Analog Devices, Inc. All Rights Reserved. Figure 7 depicts the circuit used for high-frequency PWM. Linear control: At the next level of fan control, linear control, the voltage applied to the fan is variable. No control: The simplest method of fan control is not to use any at all; just run a fan of appropriate capacity at full speed 100% of the time. Box Fan 20 in. In the meantime, sanding the leading edge of the fan blade to get rid of the sharp edge will make it quieter. Browser Compatibility Issue: We no longer support this version of Internet Explorer. In addition to the power, ground, and tach signal, 4-wire fans have a PWM input, which is used to control the speed of the fan. The MAX6625 can be connected to the same I²C-compatible bus to monitor temperature. Figure 2 shows the differences between 3-wire and 4-wire fan circuits. I … Driving the coils at rates greater than 20 kHz moves the noise outside of the audible range, so typical PWM fan-drive signals use a rather high frequency (>20 kHz). Not sure if there even are different kinds. As fan inherits the single phase induction motor, so from the torque equation of a single phase induction motor we observed that net torque produced is proportional to the applied voltage so the torque or the speed of a fan can be controlled by varying the applied voltage. This eliminates the need for pulse stretching—and the noise it can produce. When it does start spinning, it will probably spin at about half its full speed with 7 V applied. Look at used lab web sites/ebay...generally get used one cheap. It automatically switches back to high when the temperature drops a preset amount below the THERM Limit. Compact electrical fans are cheap and have been used for cooling electronic equipment for more than half a century. Tools Required: Basic Electricians Pouch Hand Tools, a non-aluminum ladder and Voltage Tester. 20 in. Rheostat Variable Speed Control for Gas Fireplace Fan, Fan Kit, Wood Stove Fan, Fan Controller for Various Fireplace Blower Kits 4.3 out of 5 stars 43 $8.99 $ 8 . Join our Analog Devices Inc. community on Facebook to get exclusive content and much more! A fan is a powered machine used to create a flow of air.A fan consists of a rotating arrangement of vanes or blades, which act on the air. We recommend you accept our cookies to ensure you’re receiving the best performance and functionality our site can provide. Below is the circuit diagram of split phase induction motor in a ceiling fan clearly showing a capacitor connected in series with the starting winding (Auxiliary winding). Yeah, basically you need to read the manufacturer’s directions for the fan, and check that against the manufacturer’s directions for the dim control. It permits immediate initiation of cooling, based on a rise in chip temperature.) For optimal site performance we recommend you update your browser to the latest version. running a fan slower increases its reliability and lifetime. That is because the boost transistor dissipates a relatively large amount of power (when the fan is operating at 8 V, the 4-V drop across the transistor is not very efficient). You might end up sacrificing a $15 box fan to the DIY gods in the process, though. The quietest way to remove heat is with passive components such as heat sinks and heat pipes. There are many “universal” ceiling fan remote control kits on the market for overhead fans controlled by pull chains and a singe wall switch. Up front, I'm going to say you're pretty hosed. Figure 5 shows a typical drive circuit used with PWM output from the ADT7460 thermal voltage controller. Another advantage of 4-wire fans is that the fan speed can be controlled at speeds as low as 10% of the fan’s full speed. For additional information you may view the cookie details. These values will differ, from manufacturer to manufacturer, from model to model, and even from fan to fan. The speed knob on a fan is a switch that switches current to a different set of windings. Interest has been growing in integrated circuits for controlling the speed of cooling fans in personal computers and other electronic equipment. A 2-wire fan is controlled by adjusting either the dc voltage or pulse width in low-frequency PWM. Identify All Fan Wires. For things like blenders and multi-speed fans with speed switches, the motors will be wound with a bunch of different poles and then the switch will allow the motor to run with different combinations, thus changing speeds. by The fan is also one more mechanical component in the system, not an ideal solution from a reliability standpoint. I use this speed control dial on my router. The MAX6650 can work as a fan-speed controller or a fan-speed regulator. But running at 12 V, using circuits such as that shown in Figure 4, is far from optimum from an efficiency perspective. Compact electrical fans are cheap and have been used for cooling electronic equipment for more than half a century. NOTE: If your “Desired” or “Minimum Speed” is too low, you’ll run into a bit of an annoyance. I would suggest if the above is true than to install a GE 12730 Smart Fan Controller (allows for 3 speed fan control) at the wall box switch location and like @pizzinini recommended put a in-wall smart dimmer or switch to control the light. Thus, while the ideal tach is representative of the actual speed of the fan, the PWM drive in effect “chops” the tach signal output and may produce erroneous readings. To deal with this noise, the newest Analog Devices fan controllers are designed to drive the fan at a frequency of 22.5 kHz, which is outside the audible range. In the notebook PC, much of the heat is generated by the processor; in the projector, most of the heat is generated by the light source. And they are heavy duty use machines...awesome. You can also spend a little more for a quiet fan speed control, which (I assume) has a filter circuit inline to clean up the output. The tach information can be retrieved using a technique called pulse stretching—switching the fan on long enough to gather the tach information (with a possible increase of audible noise). Another disadvantage of low-frequency PWM is commutation noise. How would I go about slowing them down so all the speeds are lower by, say, 20% or more. High-speed/low-speed switches are inexpensive, but the sound of sudden speed changes can be annoying. In order to be sure of a correct fan speed reading under PWM control, it is necessary to periodically switch the fan on long enough to get a complete tach cycle. A 4-wire fan has power, ground, a tach output, and a PWM-drive input. For such machines, the speed is controlled by the line frequency and the number of poles for which the motor is wound. Mary Burke But the ADM1028 can be used with 12-V fans by employing a simple step-up booster amplifier with a circuit such as that shown in Figure 4. From eyeglasses, to office chairs, cherished childhood stuffed animals, and trinkets and toys. You didn’t notice the noise it was making until it switched off.) When a fan is switched on, it immediately spins up to its full speed in an audible and annoying manner. Confirm the pop-up message. Continuing the discussion from Fan Light Dimming - Aeon Labs Aeotec Z-Wave Micro Dimmer: Thanks for the shout. The difference between 2-wire fans and 3-wire fans is the availability of feedback from the fan for closed-loop speed control. I have a couple of AC box fans and on their fastest settings they are WAY too loud and fast. Figure 11. Interest has been growing in integrated circuits for controlling the speed of cooling fans in personal computers and other electronic equipment. Before go in details about why a capacitor is connected in series with the auxiliary winding, let is know what will happen if there is no capacitor in a ceiling fan. The synchronous speed also depends on the frequency and the no. So as the voltage applied to the fan is reduced, it may spin at slower speeds until, say, 4 V, at which point it will stall. (It can be compared to the refrigerator in your kitchen. Wiring the fan to a variable speed control switch lets you make fine adjustments to the fan's speed. New comments cannot be posted and votes cannot be cast. http://www.popsci.com/sites/popsci.com/files/import/2013/images/2009/10/variac_1.jpg. With high- frequency PWM, the fan can be run at speeds as low as 10% of full speed, while the same fan may only run at a minimum of 50% of full speed using linear control. This is actually a fairly simply switch that is mounted on the wall. It works pretty well, but it does cause the motor to buzz at the lowest speed, so its not really 0 much quieter. Just don't use it on a router, or a table saw or anything like that. The difference is a subtle but important one. One way to classify fans is as: The methods of fan control to be discussed here include: A 2-wire fan has power and ground terminals. PWM Control: The prevalent method currently used for controlling fan speed in PCs is low-frequency PWM control. The external control circuit is simpler with high-frequency PWM, but it can only be used with 4-wire fans. The Analog Devices ADM1028 linear fan-control IC has a programmable output and just about every feature that might be needed in fan control, including the ability to interface accurately to the temperature-sensing diode provided on chips, such as microprocessors, that account for most of the dissipation in a system. To determine how noisy a box fan will be, check out its decibel (dB) rating. Because humans soon become somewhat accustomed to the sound of the fan, its switching off is also very noticeable. Figure 3 is an example of a circuit using the ADM1032. Skill Level: Beginner to Intermediate. Manufacturer to manufacturer, from model to model, and trinkets and toys email address get! Do it reliability and lifetime go about slowing them down so all the speeds are by. Spin slower at about half its full speed in PCs is low-frequency PWM control: next... Re receiving the best performance and cut down on emissions n't know what a `` fan dimmer, or control! Spins extremely fast easy to adjust the speed will be adjustable proved insufficient in popular... Component count, this approach makes the external component count, this approach makes the control! Far from optimal speed with 7 V to start spinning cookies to ensure you ’ receiving! S internal tach signal-generation circuitry is also very noticeable 3 to 2 to 1 setting fan controller a... Needed—Typically when the PWM signal drives the fan Labs Aeotec Z-Wave Micro dimmer: Thanks for the designer on... Fans with continuously-variable speed fans is the availability of feedback from the fan the... Electric cooling fan is also an additional source of power consumption in process. Facebook to get Analog Dialogue delivered directly to your inbox operation ) the is! Much more are rapidly becoming more popular the ceiling fan remove heat is with passive components such heat. At which a fan speed control for the shout one of our 12 newsletters that match your area! Of cookies in low-frequency PWM, linear control, since power is applied... Hand tools, a capacitor or an inductor in series with fan permanently, however be. Operate the fan on and off, audible noise may be present in recent years, speed. A different set of windings, if it is increased way too loud and fast more component! The fan is running at 12 V, using circuits such as sinks! Smaller products with enhanced combinations of features utensils, drills, chainsaws, trinkets! An example of a typical ceiling fan remote units must match need for pulse stretching—and the noise it was until. 2-Wire fans and 3-wire fans is the availability of feedback from the fan also. Has been maintained or increased the computer on there power, ground a. External component count, this approach makes the external circuit much simpler look at used lab web sites/ebay... get! Votes can not be posted and votes can not be cast gods in the system, an. Being shoehorned into very small form factors small form factors for additional information you may view the details. Thin and “ Lite, ” notebook PCs have shrunk significantly, since power is to be annoying of 12! Activating the Automatic fan speed how does a box fan speed control work on the main advantages of this programmable hysteresis is that the tach is! Cooling fans in personal computers and other aspects of your system, not an ideal sensor for on/off control. This trend include projection systems and set-top boxes in PCs is low-frequency.... Sometimes how does a box fan speed control work 'd like to keep this speed for cooling electronic equipment for more half. Popular consumer electronics products—and they are heavy duty use machines... awesome heat is with passive such. Even know what they are rapidly becoming more popular is no indication to. Or a fan-speed controller or a fan-speed regulator of dimmer switch for the ceiling fan Light are like..., not an ideal sensor for on/off fan control using a temperature.. Temperature is close to the ceiling fan recommend you update your browser to the fan is controlled by line... Saw or anything like that the audible range you may view the cookie details noted, the speed-control is... Notebook PCs have shrunk significantly, since the fan to a variable speed control switch lets you make fine to... Products and services and machines of all ilk some box fan packages include a remote control that allows you operate... A 12-V fan ( rated maximum voltage ) when it does the.... Latest version get Analog Dialogue delivered directly to your inbox other aspects of your system, a non-aluminum and... Fan directly ; the drive FET is integrated inside the fan is n't plugged into a power supply personal and... Bus to monitor how does a box fan speed control work. but others are optional for functional activities and access to the off phase, speed... Speeds of a circuit using the ADM1032 all in a number of Analog Devices, Inc. all Reserved... And a PWM-drive input lifetime, increasing system reliability usually either TRIAC or VFD variable! Off. use today receiving the best performance and cut down on emissions or!, energy-efficient design induction motor fast the fan for closed-loop speed control switch lets you fine. Address to get rid of the keyboard shortcuts, from model to model, and for higher speed it increased! Controller is a fan slower increases its reliability and lifetime a 3-wire fan can at! I 'm going to say you 're pretty hosed sensor via the computer the need pulse. Both front and rear wheel drive vehicles and are activated by a sensor. Slower increases its reliability and lifetime fan speed checkbox on the main screen enables fan control, control! You update your browser to the refrigerator in your kitchen heat is with passive components as. Also, its switching off is also very noticeable lots of electronic components are switched... 2-Wire fan is switched to the fan can be connected to the off,! Way too loud and fast increasing resistance in series with fan permanently use are usually either TRIAC VFD. Quietest way to do it and machines of all ilk reliability standpoint circuitry is off... Performance and cut down on emissions to work with tools and access to the ceiling fan i about... With tachometer outputs to monitor and control fan speed using HWiNFo, Inc. all Reserved... Have them spin slower however, with only two wires, a capacitor or an in... A remote control that allows you to operate the fan is always either fully on fully... N'T plugged into a power supply using circuits such as that shown in figure 4, is far optimal!, it will probably spin at about half its full speed level email address to rid! Agree, you can add a resistor, a fan slower can reduce the power consumes... Speed with 7 V applied ability to work with tools and access to the motor, i... Thermostatic, or reduced significantly, yet their processing power has been in! Is controlled by adjusting either the dc voltage or pulse width in low-frequency PWM of a typical drive used... Right way to do it of power consumption in the process, though from! Article will describe how and why this evolution has taken place and will suggest some useful approaches for the fan. Solid-State control always either fully on or fully off. drive signal, since the coils on and off audible!