DC Motor Speed Controller

Discussion in 'General Electronics Chat' started by Lanz, Jun 10, 2009.

  1. Lanz

    Thread Starter Active Member

    Oct 30, 2008
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    Hi,i serviced my car blower myself recently and found out the speed controller is out of fashion.The speed of the blower motor is controlled by some filaments.So this filament get hot and the air blowed by the blower also hot.I know the manufacturer of the car use filaments because they want to control the speed via different current and not with different voltage because the voltage of the motor fixed to 12VDC.The problem is if using filament,the air is hot and filament consume more battery power.Now i want to change the speed controller using nowadays technology.
    I had searched over the net and most of them suggesting PWM which uses microcontroller and thats hard for me because i dont have any programmer.
    I just want a simple and easier circuit if can.
     
  2. beenthere

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  3. Lanz

    Thread Starter Active Member

    Oct 30, 2008
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    Thanks beenthere.
    Can it support high amp because car battery has high amps.
     
  4. Externet

    AAC Fanatic!

    Nov 29, 2005
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    ¿¿¿¿???? :(
     
  5. Lanz

    Thread Starter Active Member

    Oct 30, 2008
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    High amps i mean is high current.
     
  6. beenthere

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    Apr 20, 2004
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    The IRF510 won't handle the current (from the fan), but you can get an IRF1302BPF for $3.19 that can be driven from the circuit. It is good for 180 amps and 230 watts. It will need a big heat sink to dissipate heat.

    Get the data sheet for the FET so you know what lead is what.
     
  7. Lanz

    Thread Starter Active Member

    Oct 30, 2008
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    Thanks for the info Beenthere.
    Anyway whats the ampere range of the car battery?
     
  8. kammenos

    Active Member

    Aug 3, 2008
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    40-80-120 Ah

    In simple words, it can suply 40-80-120 amperes (in perfect conditions always) for an hour. The amount of amperes that you will draw from the battery has nothing to do with this value. The amount of amperes has to do with the resistance of your circuit and the voltage of the battery.

    I = U / R

    This means that if you have a 12V 120Ah battery (big one for a car), and you connect a lamp with 10 Ohms resistance, it will draw current:

    I = U / R => I = 12 / 10 => I = 1.2 Amperes.

    And this will also be the same even if the battery is 40 Ah or 80Ah....

    You could also take a look at this circuit.
    It may fit your needs
     
  9. Lanz

    Thread Starter Active Member

    Oct 30, 2008
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    [​IMG]
    Thanks Kammenos.
    The circuit is simple and nice.
    Can i directly connect the 12V circuit supply input to the car battery or do i have to use regulator?
    The high current from the battery wont spoilt the components especially 555?
    From the picture i know that the MOSFET send current to the motor to spin.
    But whats the MOSFET's function actually(why need to use that)?
     
    Last edited: Jun 11, 2009
  10. kammenos

    Active Member

    Aug 3, 2008
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    Yes you can connect it directly to the 12V of the car. Even when the battery is chargin (13.2V) yo wont have problems. It may be that the fan will rotate a little bit faster but no problem.

    The mosfet is used to drive the fan, as the 555 is not able to drive such loads.
     
  11. R!f@@

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    Apr 2, 2009
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    Just wondering....the heater's...arent' they used to produce heated air..if so talking them out is not suggested and the speed is adjusted in such a way that the air flow and heat produced are related.
    Like more heat and higher air flow, Low heat at low air flow..

    ___________________
    Rifaa
     
  12. Lanz

    Thread Starter Active Member

    Oct 30, 2008
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    Thanks for the info.I will try the circuit.
     
  13. Lanz

    Thread Starter Active Member

    Oct 30, 2008
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    Yes,but that heater is only for cold country and in my country the climate is hot,so its better to take it out.
     
  14. R!f@@

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    Ok. then PWM is just what you need. Just remember the driver is powerful enuf
    _________
    Rifaa
     
  15. Lanz

    Thread Starter Active Member

    Oct 30, 2008
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    If this circuit really works with my fan means my car will have high technology with latest circuit.My car is old enough built in year 1982.Hope it works.I dont know weather i can get all the components or not.Is the 555 Ic mentioned there means NE 555?Are 0.1nF and 10pF is ceramic or electrolytic capacitor?Please give me the capacitors voltage?Tomorrow im gonna buy the components.
     
    Last edited: Jun 12, 2009
  16. R!f@@

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    Apr 2, 2009
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    yup!!! ceramics, working voltage should be more than Vcc.
    Ceramics are rated at minimum 50V as I have come across.
    ______________________
    Rifaa
     
  17. Lanz

    Thread Starter Active Member

    Oct 30, 2008
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    [​IMG]

    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?
     
    Last edited: Jun 16, 2009
  18. Lanz

    Thread Starter Active Member

    Oct 30, 2008
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    1N5815 diode is not available.What other diodes that can be used as a replacement?
     
  19. jpanhalt

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    Jan 18, 2008
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    For the 1N5815 diode shown in the schematic, any small signal diode will work. 1N4148 are common as are 1N914, but really almost any diode will work.

    John
     
  20. themotorman

    Member

    Jun 13, 2009
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    Please explain the cap function? Also using a 100K pot and a 10pf cap gives a frequency of about 2/RC Hz. or in this case 2/0.1 x 10 x 10^-6= 2 Mhz much too high . I would think that a frequency of 15 Khz would be much better .. high enough not to be heard and also not too high for switching losses to be a factor.
    Did you mean 10nF ? That is 10 x 10^-9 F so frequency would be be 2 Khz , you could hear that loudly coming from the motor...or is that what the cap is for !! I think that's it. ??
    I would suggest a 10 K potentiometer and use a 100 nF cap. same frequency but less sensitive to picking up noise, especially if controlle ris remote form control pot.
     
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