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  1. Lazzer408

    So you want PWM control of your 3-pin fan?

    It's going to be something along these lines. Not sure how it will work with the PWM signal being 5v but a low/hi signal driving this circuit will give you a low/hi out. Choose a Q1 large enough to drive your load, Choose R2 to drive enough current into Q1's base. Q2 should be large enough to...
  2. Lazzer408

    So you want PWM control of your 3-pin fan?

    High side switching via. MOSFET will require gate drive >12v. Use a BJT transistor. Because it's switched mode, losses are minimal. Typically (.6V*A)*PWM=dissipation. If you had 3 amps worth of fans (a lot), and PWM is 100%, you will only have ~1.8w of heat to dissipate from the transistor. I'm...
  3. Lazzer408

    So you want PWM control of your 3-pin fan?

    All of that had been mentioned in the thread.
  4. Lazzer408

    So you want PWM control of your 3-pin fan?

    The capacitor should be placed in parallel with your supply voltage. Duty cycle (pulse width) is controlled by the motherboard. If you can't adjust it in the BIOS then there's nothing you can do about it.
  5. Lazzer408

    So you want PWM control of your 3-pin fan?

    The PWM frequency is a function of the motherboard. All the board does is ground the PWM pin at varying widths. If you don't have complete control over the fan curves in your BIOS, this circuit may not work for you. The "correct" way to control a fan (using Intel's PWM spec) is a more...
  6. Lazzer408

    So you want PWM control of your 3-pin fan?

    Put your meter on AC and measure that charger. Read anything? If so, that's the ripple in the DC caused by the chargers lack of filtering (they don't need it). Next, place a capacitor in parallel with the charger and measure the DC voltage. Is it higher? If so, that's the peak DC voltage coming...
  7. Lazzer408

    So you want PWM control of your 3-pin fan?

    I think it's in quotes because we have no idea of knowing what type of charger it is. If it's a trickle charger for lead acid batteries, then it's likely much higher then 12v and it's not DC either. If the fans run full speed with the PWM unplugged, your gate drive is ok. What happens with you...
  8. Lazzer408

    So you want PWM control of your 3-pin fan?

    He mentioned in #79 that he tried the charger... "with a few Deltas and San Aces, 8 fans total, they all seemed to run full bore with no PWM connected". I think it's in his computer now.
  9. Lazzer408

    So you want PWM control of your 3-pin fan?

    Not a very good component but RDS(on) at 4v is .07 ohms so you 4.1v is plenty of gate voltage. NTE parts are junk (for future reference) but not the cause of your problem. The switching frequency is a function of the motherboard and should be around ~20khz. What do the fans do if you pull the...
  10. Lazzer408

    So you want PWM control of your 3-pin fan?

    Are you using a logic-level mosfet?
  11. Lazzer408

    So you want PWM control of your 3-pin fan?

    Which hurts who in what way? Information doesn't have a "sell-by" date. If people are still benefiting from the thread, it's not dead.
  12. Lazzer408

    So you want PWM control of your 3-pin fan?

    What's that have to do with anything?
  13. Lazzer408

    So you want PWM control of your 3-pin fan?

    Sounds like it's working fine. Good job.
  14. Lazzer408

    So you want PWM control of your 3-pin fan?

    Connect it to your 12v source. PWM lead should have ~5v on it. With PWM lead disconnected, the fan should run full speed. With the PWM lead grounded, the fan will stop. I'll look over your pics tonight. Velict's diagram looks fine other then the diode's anode connection doesn't have a dot...
  15. Lazzer408

    So you want PWM control of your 3-pin fan?

    Did you bench test it?
  16. Lazzer408

    So you want PWM control of your 3-pin fan?

    I'm going to add another circuit to this thread that may help you guys. This circuit CREATES a PWM signal that can be used to manually control 4-pin fans. The potentiometer is labeled "throttle" because this was part of a DC motor controller I'm designing. Frequency is controlled by C1. R7 may...
  17. Lazzer408

    So you want PWM control of your 3-pin fan?

    Looking at the schematic in post 7, you can probably eliminate R1 and Q2 and place the zener where Q2 was. When PWM calls for full speed, you should see ~11.45v on the fan due to the C-E voltage drop across Q1. When PWM calls for 0, the minimum speed is set by the 100k variable resistor...
  18. Lazzer408

    So you want PWM control of your 3-pin fan?

    None of the fans are modulated by that circuit itself. The circuit is just a switch being modulated by the motherboard's PWM pin. As for the PWM pin... PWM high (5v or not connected) = Fan at 100% PWM low (grounded by motherboard) = Fan at 0% PWM 50% = Fan at 50% (6v) The schematic you just...
  19. Lazzer408

    So you want PWM control of your 3-pin fan?

    Glad you figured it out. How is it handling the load of so many fans?
  20. Lazzer408

    So you want PWM control of your 3-pin fan?

    The reason they use PWM is because it's a switched-mode method of controlling analog devices like motors, lamps, LEDs, etc. and that's second nature to digital electronics. It's also more efficient and cost effective then a linear voltage regulator. The switching devices (carrying the current...
  21. Lazzer408

    So you want PWM control of your 3-pin fan?

    The fan should be running at full speed if the PWM signal isn't attached. Check for ~5v between gate and source.
  22. Lazzer408

    So you want PWM control of your 3-pin fan?

    Correct. Multiple PWM fans running off a single PWM signal can cause issues because the PWM spec calls for very little current on that pin. Spec calls for a PWM fan to provide no more then 5.25v at no more then 20ma of current (if I remember right). This is probably used for detecting the...
  23. Lazzer408

    So you want PWM control of your 3-pin fan?

    It is true that the PWM signal has a limit but this circuit only uses the PWM signal to switch the mosfet's gate on and off. What's on the other side of the mosfet is invisible to the PWM signal from the board. You can connect as many fans as you want as long as the total current draw is less...
  24. Lazzer408

    So you want PWM control of your 3-pin fan?

    Then either I'm misunderstanding what your doing or your misunderstanding how the circuit functions. You don't need to boost the PWM signal. Intel's PWM spec is more then enough to sink gate drive.
  25. Lazzer408

    So you want PWM control of your 3-pin fan?

    Ok just trying to get it straight. You don't need to "boost" the PWM signal. What is your reason for the 556?