Simple PS3 Fan Speed 555 Pulse Mod No Pots
Posted 16 January 2011 - 10:40 PM
I've been playing with my 555 pulse timers and figured I'd post what I've done so far as there really doesn't seem to be a decent schematic online anywhere.
I didn't want any potentiometers, I don't want the owners turning the fan down. Just a simple 555 timer schematic for running the fan at a decent rate.
Runs off the fans 12V Brown wire so no need to wire from another source. To regulate the pulse peek voltage to 3V I used a common LED and it also helps to visually gauge the pulse frequency.
With 4.7K ohm at R1 it is still quite fast and about as loud as a 360 12V Mod. Combining resistors to make around 5K ohms or so should quiet it down a bit more. You can change the C1 from 1uF to 10uF but then you must change the R1 value accordingly.
Posted 17 January 2011 - 12:20 AM
Posted 28 January 2011 - 12:51 AM
One good thing about this is you can substitute many different value resistors and caps and still get the same ~50% fan speed. Only if the frequency gets too low you will hear the fan turn off and on. Like below 20 Hz. the frequency in the schematic is quite low, I'm told the actual fan pulse is 25Khz with 20% duty which is too slow. It is the duty (percentage of time the pulse signal is high) that really determines the fan speed.
If I can get around to it I will post a ~35-45% Mod later on that needs an extra diode and resistor but it's not a big priority for me.
If anyone had ideas to make this pulse mod even simpler, please post but remember I'm not interested in adjustable POT mods. I want a decent speed FIXED mod. Users will just turn a POT to it's lowest setting anyway. I'm not making these for myself, I don't own a PS3.
Posted 29 January 2011 - 04:24 AM
As it says you could replace R1 with a combination resistor + POT in series to fine tune.
I suspect you can use probably use any Capacitor from .1 to 10uf for C1 as the actual frequency doesn't affect the fan too much. as long as it's between 30Hz and 25Khz.
Posted 01 July 2011 - 07:37 PM
Posted 18 July 2011 - 09:18 PM
gostaria de montar este esquema mas tenho duvidas quando ao 555.
Qual foi a referencia que usas-te?
Here's another diagram 50% speed without using the LED. This is how I've been doing them recently:
Posted 24 July 2011 - 11:22 PM
They were using the 555 chip to blink LED's for halloween costumes.
Also some info here:
So the schematics using the LED is to reduce the 12V output to 3.3V pulse peek. The only problem with this is if the LED ever dies the Fan pulse will peak to around 10.5 volts or so and possibly damage the fan. I realized this from the beginning and decided it was an acceptable risk. The 555 chip can handle being powered at 12V and if I remember correctly the output at pin 3 is around 1.5V lower than the power voltage. The whole reason I did it like that as I wanted the whole mod attached to nothing more than the 3 fan wires, fore convenience mostly. Now if you power the 555 chip from the PSU 5V line like my last diagram there is no need for the LED to drop the voltage for the fan pulse line, the pulse output should peak at 3.5V.
Posted 13 August 2011 - 12:20 AM
I do have an install pic:
This one is the diode version. Different capacitors and diodes require different value resistors to get the speed just right when using the diode variable duty version.
After soldiering I just wrap in tape and tuck in over the fan connector.
Posted 30 September 2011 - 09:33 AM
Posted 05 October 2011 - 11:48 PM
Posted 01 November 2011 - 02:48 PM
Posted 02 November 2011 - 12:33 AM
Posted 04 November 2011 - 11:04 AM
I used 3x 1.8k resistors at R1 to get the level I wanted.
Posted 16 December 2011 - 01:04 AM
I have 2 questions:
1) Increasing R1 is there a limit?
2) Cutting a hole in the the top just over the fan about 1 and a half inches is it a good idea. I am not sure because air will be suck thrue that hole instead of hole around the unit to cool all parts of the unit.?
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