Using this fan speed controller circuit you can control the speed of 12V DC fans used in cars.

Why and How to Control Fan Speed for Cooling Electronic Equipment

The circuit is built around timerwhich is wired as an astable multivibrator. Capacitor C1 is connected in parallel to the fan to stabilize its speed. Free-wheeling diode D1 protects the motor from back emf. A fuse is included for protection. Potmeter VR1 is used to change the duty cycle of the multivibrator and hence the speed of the fan. Assemble the circuit on a general-purpose PCB and enclose in a suitable cabinet. Fix the potmeter at the front side of the case, so that you can easily change the speed of the fan.

Connect the battery to the fan using wires with suitable current-carrying capacities. Use red wire for positive terminal and black wire for negative terminal. Sign in Join. Sign in. Log into your account. Sign up. Password recovery. Wednesday, April 15, Advertise Contact About Magazine. Forgot your password? Get help. Create an account. Electronics For You.By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It only takes a minute to sign up. As I am planning the circuit and I certainly can be wrong in my calculationsI plan to have a 12V power source 8AA batteries in series. I am trying to use a PN transistor to control the fan's speed.

According to my calculations, I would need 6mA into the base of the transistor to get the mA needed to run the fan at or close to full speed. So, then to control the speed from there, i. Connections: Negative rail connected to Emitter and 2K Resistor which also connects through thermistor to base.

Collector is connected to negative side of fan. Positive rail connects to positive terminal of fan. I believe I have included all the pertinent information, but if I left something out, I'll be happy to add more. So, the problem I am having is that the fan doesn't even turn. I have connected the fan directly to the battery source, and the fan turns. I have started some basic troubleshooting, but found that I am reading 0V across the 2KR 1.

So, I guess my question is what am I missing here? Why can I not get the fan to turn in this circuit, and I am sure it is probably something stupid. I might have missed something in your question, but the transistor base needs to be positive with respect to the emitter to turn on.

The transistor base is currently connected to the emitter. As a heuristic solution, you can use a potentiometer to see at what point the fan will turn on, then size your resistor and thermistor accordingly. I am thinking you want something like this, using a mosfet it can handle more current and using the "pot" makes it temperature variable.

Sign up to join this community. The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. Asked 2 years, 8 months ago. Active 2 years, 6 months ago. Viewed 2k times. Jonathan Jonathan 13 6 6 bronze badges. BTW you haven't actually asked your question. You're probably going to want to have your transistor as an emitter follower and be thinking voltage control rather than current limiting as you seem to be as that is dependent on the highly variable gain of the transistor.

Also, a 2n is going to get quite hot, you might want something beefier in a TO package. I also added some additional information of what I have tried so far to troubleshoot.

As for the transistor, I believe it is a TO package, according to the datasheet that I have for it. Also, this is not going to be running long-term. I don't know how quickly the transistor will heat up, but I am only trying to get this running to prove the concept.

This is not for a real-world application No need to shy away from micro controllers with the Arduino platform. Active Oldest Votes.In continue to an older set of circuits Simple Ways to Make Fans Silenti decided to fulfill the fan controller circuits. Until now, i have present several PWM circuits to control a fan, yet these are rather difficult for a simple PC moder to implement. The latest circuit post was a set of some circuits so easy, that even a kid can do.

But They did not provide linear control. Therefore, here i am again, with the simplest linear fan controller circuit. The circuit is composed by 6 components: 2 resistors, 2 capacitors, the potentiometer and a transistor. The potentiometer is connected as voltage divider. The two resistors will set the highest and lowest value of the voltage divider. The output is driven directly to the base of the power transistor.

The two capacitors are to smooth the voltage, as i saw some "waves" in the oscilloscope during the test-runs. C1 can be omitted, as i put it only to straighten the curly base voltage. The circuit was working perfect even without it, but why removing it anyway? It is ridiculously easy! Can be mounted on a tiny pre-drilled PCB, with the potentiometer on one edge. The rest of the circuit will be behind the potentiometer.

12v fan speed control circuit

The circuit is designed to be powered directly from the power supply of the PC check the Power supply pinouts and get 12V from wherever you can. Yes of course it did. The output voltage varies from 5 to 12 V. In case that your fan does not revolve with so low voltages, just increase the R3 a little bit. Here are some images from the oscilloscope, reading the tach of the fan:.

There is a major drawback though. This circuit has a very bad habit. It generates a lot of heat on the transistor. I was rather surprised by the amount of heat. When i was making the PWM circuits, i ran some test with multiple fans connected in parallel, just for fun. Now, with a mA fan, the transistor is getting hot.

I suppose that for bigger fans, you may consider using a heatsink. Nevertheless, the only "problem" with this is that it does not have a really good efficiency. It will operate without problems. The reason for all this heat on the transistor is the operation of the circuit itself. When the fan runs in full rpm, the transistor will strangely generate almost no heat at all!

This is normal though if the fan is within the current limits of the CE contact of the transistor. The problem begins when the circuit is asked to reduce the speed of the fan. To do so, the transistor will dissipate an amount of power. The more the power the transistor dissipates, the lees the power delivered to the fan! This is how the fan runs slower. As you understand, when the fan runs with the lowest speed possible, the transistor will dissipate the highest amount of power.

Thus, the circuit is most efficient when the fan runs at high rpms.Here is a simple circuit based on two transistors that can be used to control the speed of a 12 V DC fan depending on the temperature.

A thermistor R1 is used to sense the temperature. When the temperature increases the base current of Q1 BC increases which in turn decreases the collector voltage of the same transistor. Since the collector of Q1 is coupled to the base of Q2 BDthe decrease in collector voltage of Q1 forward biases the Q2 more and so do the speed of the motor.

Also, the brightness of the LED will be proportional to the speed of the motor. I trust this circuit more. I like to adopt an 12 V DC fan into my television for cooling purpose. Motor speed need to be adjusted. Well this circuit is adequate and i gonna to try this.

Need notes on the functions of the individual parts of a temperature control fan, how the circuit operates and how it will stop operating to assist me understand the project. Author admin. DC motor controller January 22, H Bridge motor control circuit using L February 9, Motor driver using TC January 6, Anthony 7 years ago.

Sulaiman Koroma 9 years ago.

12v fan speed control circuit

Arnie Nutini 10 years ago. Submit Type above and press Enter to search. Press Esc to cancel.Interest has been growing in integrated circuits for controlling the speed of cooling fans in personal computers and other electronic equipment. Compact electrical fans are cheap and have been used for cooling electronic equipment for more than half a century. However, in recent years, the technology of using these fans has evolved significantly. This article will describe how and why this evolution has taken place and will suggest some useful approaches for the designer.

The trend in electronics, particularly consumer electronics, is towards smaller products with enhanced combinations of features.

Consequently, lots of electronic components are being shoehorned into very small form factors. An obvious example is the notebook PC.

Other examples of this trend include projection systems and set-top boxes. 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!

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.

Fan Speed Controller _ Dc 12 Volt Motor Speed Controller Switch

This heat needs to be removed quietly and efficiently. The quietest way to remove heat is with passive components such as heat sinks and heat pipes. However, these have proved insufficient in many popular consumer electronics products—and they are also somewhat expensive. 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.

A fan is a source of noise, however.

Temperature controlled DC fan

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. The fan is also one more mechanical component in the system, not an ideal solution from a reliability standpoint. 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.

We will discuss here various fan types and the advantages and disadvantages of control methods in use today.This whole process is done automatically.

We have previously made the Temperature controlled Fan using Arduinowhere the speed of the fan is also controlled automatically. Thermistor is temperature sensitive resistorwhose resistance changes according to the temperature.

12v fan speed control circuit

NTC thermistor is a resistor whose resistance decreases as rise in temperature while in PTC it will increase the resistance as rise in temperature.

Check here the Fire alarm circuit using Thermistor. An operational amplifier is a DC-coupled high gain electronic voltage amplifier. An operational amplifier IC is used as a comparator which compares the two signal, the inverting and non-inverting signal.

The main function of this IC is to do mathematical operation in various circuits. The application of this IC mainly includes an adder, subtractor, voltage follower, integrator and differentiator. The output of the operational amplifier is the product of the gain and the input voltage. Check here for other Op-amp Circuits. It works on the principle of thermistor.

As the thermistor return to the normal condition the fan will automatically turn OFF. What if I use 12 volt for the input power and also DC fan that rated 12v? Is the circuit IC and transistor can handle more than 1 ampere current? Thank you, sir. Hi andi. No it cannot handle that much current for 6 fans. You have to use individual op-amps. What is the watts of the potentiometer, ntc themistor and npn transistor and also the ampere of the power supply?

Will this work using 3 volt supply. I've connected everything up using a 3 volt led and this stays on constantly with no change when I adjust the pot. No it will not work.This instructable should help you build a simple 3 speed fan controller for any 12v dc computer fan. I couldn't find a decent tutorial on fan controllers so i've made this simple one. This is my first Instructable so I hope it's alright : Please comment I can't be held responsible if you break stuff, i have tried to describe things as thouroghly as possible but if stuff breaks it's your fault not mine.

Did you use this instructable in your classroom? Add a Teacher Note to share how you incorporated it into your lesson. First Chop the molex plug off the end of the fan wires,get as close as you can as it will give you more wire to work with later. So then you should have a fan with a red wire and a black wire coming out and nothing on the end of them.

My fans had pass through molex connectors so you can connect several fans using only one molex outlet on your PSU, if yours does also then clip the end off like in the picture, you want as much wire as possible on the end we're keeping to make soldering easier.

Fan speed controller using LM2941

Soldering starts now, so plug in your iron. Add an extension bit of wire to make soldering to the switches easier, thats the blue wire in the picture. Tape or heatshrink your soldered wires to insulate them. Get your molex plug we saved earlier and twist the two black wires in the middle together and solder them to the other side of the on off switch with some wire. So the speed change will be because of the switch between the two volages a molex plug provides.

Yellow is 12V Full speed Red is 5V Half-ish Speed Solder the yellow molex wire to one of the outside pins on the SPDT switch and the red one on the other side, extend if you need to, i'd reccommend adding some extra wire in as other wise you may struggle when fitting into your case.

While youre soldering the switch solder another wire onto the middle pin and leave the end free for the next step. If you have an old PSU, use that! Once again it's not my fault if you break something Including yourself during this stage or any other. Unplug the PSU from the mains. Unplug the leads into your motherboard and drives, un screw the PSU and it should lift out of the case.

There are loads of youtube videos that will help you with this so i'm not going to go into any more detail than that.

Now it's removed, find the green wire in the big bunch that went to the motherboard It's pin 16 See picture Then get a small pece of wire and connect Pin 16 Green to pin 15 Black This makes your PSU think it's attatched to a motherboard, otherwise it won't turn on Now turn the PSU on and connect the Fans Plug it back into the mains don't forget Turn your PSU on, the fans should come on when you throw the fan switch to on, and should be fast and slow when you use the other switch Disconnect everything and put it back in your case.

It's up to you how you mount the switches into your case, you can use empty drive bays or just put them in the case roof.

DIY PC Fan Controller

If you add enough wire theres no reason why you cant have them in an external box on your desk or something Hope ths is useful to you, I'll be glad to hear your comments. JelleW1's post pointed out the main problems. But there is more to point out here. Do not bild blindly Also I would not use the same PSU again in my main station after this "cripling" short- circuit trick Reply 3 years ago.

Also fans have start up problems on low voltages. If you get a to low voltage and your fan does not start up it could burn though and set on fire. Figured I had better ask before hand even if it is a stupid question. Reply 5 years ago on Introduction.


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