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1 January 1970
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  • At 11 March 2010, 22:29:54 user PDS wrote:
      • I'm a little confused. Sorry for the basic question, but I've built this circuit, and it works beautifully. I had to swap a 1uF cap instead of the 10nF as suggested for my particular fan, but I get a smooth speed variation between almost stalled and full speed. (Average voltage from 5V to 12V.)

      However, when I compare this circuit to a standard Astable Multivibrator, pins 3 and 7 appear to be reversed (?). Typically, pin 3 is the output and pin 7 is the discharge. I understand the variable resistor and diode change, but how can this work with the output swapped with the discharge pin?

      Sorry if this is a dumb question, but I'd like to understand *how* it works as well as using it myself. Great write-up BTW - even *I* could follow it.

  • At 24 October 2009, 5:51:13 user kammenos wrote:
      • Yes Lanz you are right. I'm sorry. I will fix this ASAP. The correct value is 1K

  • At 22 October 2009, 4:36:08 user lanz wrote:
      • The resistor in the picture shows 1K but the description shows 10K?

  • At 14 July 2009, 12:26:38 user theking wrote:
      • See the following link:
      http://www.micrel.com/page.do?page=/product-info/products/mic502.shtml

  • At 12 July 2009, 18:48:05 user kammenos wrote:
      • Lanz:
      The 470 capacitor needs to be placced across the mosfet. That is the right place. For better control, you can change the frequency by adding larger capacitor in place of the 10nF (eg 1 micro farad instead), or with larger potentiometer value (eg 500K). That shoud fit you just fine.

      For LED dimmer, you only need to remove the 470uF capacitor completely and add the correct resistance according to your LED configuration you use. Check out the following pages for this:
      http://pcbheaven.com/wikipages/LEDs/
      http://pcbheaven.com/drcalculus/index.php?calc=leds

  • At 10 July 2009, 9:19:19 user lanz wrote:
      • Finally it works for me.But still got some problems:
      1)I test it without the 470μF Cap,there is kicking sound like what kamenos said but the difference in speed can seen very well with every turn of the VR.
      2)I test it with the 470μF Cap placed parallel across the motor like the circuit b4 this and second time at the mosfet like the circuit above,the kicking sound is no more but the speed differ only slightly(not nice).

      I like the 1st one but there is a kicking sound.How to solve this problem?
      If want to use as a LED dimmer,where to modify?

  • At 10 July 2009, 9:18:25 user lanz wrote:
      • Finally it works for me.But still got some problems:
      1)I test it without the 470μF Cap,there is kicking sound like what kamenos said but the difference in speed can seen very well with every turn of the VR.
      2)I test it with the 470μF Cap placed parallel across the motor like the circuit b4 this and second time at the mosfet like the circuit above,the kicking sound is no more but the speed differ only slightly(not nice).

      I like the 1st one but there is a kicking sound.How to solve this problem?

  • At 10 July 2009, 5:30:38 user lanz wrote:
      • Thats why maybe it doesnt work on my circuit.How to test the output on multitester,volt reading or current reading?

  • At 9 July 2009, 16:48:38 user kammenos wrote:
      • Oh, and as for the capacitor, it may be omitted if someone wants PWM for the motor. If the motor kicks (the distinctive kicking sound) then the large capacitor must be connected. It is across the mosfet now.

      My apologies for the mistake. The circuit was copied in a hurry and was also the first one.

  • At 9 July 2009, 16:39:38 user kammenos wrote:
      • But of course, how stupid of me. I confused n with p. My apologies. I have changed and corrected the schematic.

      Thank you theking very much for your comments and noting this error.

  • At 8 July 2009, 12:21:59 user theking wrote:
      • 1 pF = 0.000001 uF;
      1 uF = 0.000001 F;
      C = 10 pF => 0.000000000010 F
      R = 100 K => 100000 OHM
      R x C = 0.000000000010 x 100000 = 0.000001
      F = 1.44/(RxC) = 1.44/0.000001 = 1.440.000 Hz (1.44 MHz)

      Check your math.
      The minimum value of C to 555 works correctly is 1KpF (1000 pF) and the 470uF cap across the motor is not correct for a PWM circuit.

  • At 8 July 2009, 4:41:51 user kammenos wrote:
      • The video is from this circuit, so this is the first clue that it does work after all.

      You have an error in your calculations by selecting the proper units:
      R=100K => R = 100.000 Ohms
      C=10pF => C = 0.00000001 F

      F = 1.44 / (RC) => F = 1.44 / (100000 x 0.00000001) => F = 1440 Hz

  • At 8 July 2009, 1:17:08 user theking wrote:
      • This can not work!
      The 555 oscillation frequency is:
      1.44/RC = 1.44 / 0.1 (Mohm) x 0.00001 (uF) = 1.44 MHz

      The 555 does not operate at this frequency!

  • At 29 June 2009, 18:30:53 user kammenos wrote:
      • lanz:
      1. The protection diode could be a general 1N4001 diode, but if you use the 470UF capacitor, you do not need it.

      2. If you want to use a fuse protection, you should put it in series to the circuit. The circuit itself draws just a few mAmps, thus the fan will determine the fuse. You could as well calculate the fuse by the IRF520 capacity that is 9.2 amperes. In that case, you could use a fuse around 8 Amperes.

      3. From pin 8 or 4 of the 555, a resistor of 330 Ohms will be connected and then the positive pin of the LED will follow. The negative pin of the LED will go to negative pole of the circuit.

      4. I am sorry this cannot be done with straight-forward way. You could use a digital potentiometer circuit or IC, but that would be not a nice solution.

  • At 29 June 2009, 7:38:49 user lanz wrote:
      • 1)What is the protection diode's value that to be fixed parallel to the motor?eg.like 1N5815 for the left diode.

      2)If i want to fix protection fuse,the maximum capacity of the fuse must be how many ampere?How to check it using multitmeter?

      3)I want to add a LED as an indicator showing the circuit is working and the fuse is not blown.How to modify the circuit above?

      4)Can the potentiometer replaced with any pushbutton switch?
      Example-Two pushbutton switch is used to control the volume of a sound.
      One to increase and one to decrease the volume.
      Can this system applied in this circuit?
      If can,how is the circuit will be?

  • At 12 June 2009, 4:22:53 user kammenos wrote:
      • Yes indeed, different fans or loads will require different PWM frequency. If the load draws too much current, it could be that the frequency should be increased (decrease the cap value) and vice versa.

  • At 11 June 2009, 21:37:45 user Tiki wrote:
      • Nice and is working, but with my Glacialtech fans i needed to replace the 10pF with a 47pF to get a large and smooth area of control.

  • At 11 June 2009, 15:18:08 user Kammenos wrote:
      • Yes no problem!
      The circuit will draw as much current as it needs. If there is no short-circuit, all will work just fine. You could for security reasons add a quick acting fuse in series to the power supply if you may.

  • At 11 June 2009, 4:50:25 user Lanz wrote:
      • Can i use this circuit to control my car\'s fan speed.Can it support high current from the car battery?

  • At 4 June 2009, 17:41:49 user kingsley wrote:
      • wow this circuit is great

  • At 4 June 2009, 16:38:23 user kammenos wrote:
      • Hi XTAL.
      The purpose of this project was (and is) the PWM signal generation. That's why the capacitor (470uF) is added at last. This project can be used in general for example dimming LEDs. Also, this project is a small research for the next circuit that i will demonstrate (hopefully this weekend). My PC box has 4x120 fans and 2 computers inside, as well as some peripherials like a router, switch, electronic staff....

  • At 4 June 2009, 12:00:47 user CrystalRadio wrote:
      • Now that the fan\'s tach signal can be used by the motherboard, how about using the motherboard\'s fan control output to control the 555 circuit? There would still be a need to adjust the min speed for each fan to create a broader speed range than would be possible using the motherboard\'s fan speed output alone.

      Good Work! Good Luck! And Goomorning! XTAL

  • At 21 May 2009, 22:08:06 user kammenos wrote:
      • Go for it. It's easy and it works. We wait for your project photos

  • At 21 May 2009, 1:35:05 user bravo wrote:
      • I wonder if Im smart enough to do this one yet I got 3 80mm tsunami that kick out wicked af but no controllers for them and their 3 wire hook up

  • At 18 May 2009, 12:48:32 user kammenos wrote:
      • meant 1.55 US dollars ;)

  • At 14 May 2009, 19:55:54 user kammenos wrote:
      • and a total price of 1.55 (excluding the PCB and the box) makes it the cheapest fan speed controller :D


     

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