Jump to content
Electronics-Lab.com Community

HELP - resistors and dip-switch


Virus
 Share

Recommended Posts

  • Replies 64
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Posted Images

Allvol

How was your golf day?

Thanks for the links, interesting info.

The best I can describe for you what I want to do is, if it is at all possible for you to build the circuit in Rely 14, 3 components only.

You can adjust the trim pot for the fans to come to a dead stop when your PC is cold, just switched on, with the thermistor in place close to the CPU heatsink, ( by playing around until you get a good position for the thermistor) it will easily control the fans from 0 % to

Link to comment
Share on other sites

GM, Virus

From the 4QD website: In a practical low voltage controller the switch opens and closes at 20kHz (20 thousand times per second). This is far too fast for the poor old motor to even realise it is being switched on and off: it thinks it is being fed from a pure d.c. voltage. It is also a frequency above the audible range so any noise emitted by the motor will be inaudible. It is also slow enough that MOSFETs can easily switch at this frequency.

Measure the frequency at pin 3 of your 555 without the thermistor in circuit.

Link to comment
Share on other sites


In a practical low voltage controller the switch opens and closes at 20kHz (20 thousand times per second). This is far too fast for the poor old motor to even realise it is being switched on and off: it thinks it is being fed from a pure d.c. voltage.

Doesn't the inductance of the motor reduce its max current at the higher frequency?
Link to comment
Share on other sites

Guys

By whisper I meant irritable, nagging, down warring sound, doesn’t mater how soft it is it will catch on to you. I will accept a whisper any day.

What the use of trying to get rid of the fan noise, and replacing it with electronic noises.

Can PWM on a 12v case fan’s, be quiet enough, to be used in this task, or should I stick with the original diagram (reply no 14).

There’s got to be a way.

Virus

Link to comment
Share on other sites

You can use the fan's driving transistor as a completely quiet variable resistor, then it gets hot.
You can use PWM at a frequency above 20kHz so it is completely quiet, and it doesn't get hot.
You can use a bigger fan that can turn slower to move as much air as a smaller fan running faster, and the noise will be much less.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
 Share


×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.