Ever wished
those noisy fans weren't on all the time? or
dont see the point in them being on when the
computer isnt doing anything? Well, I can help
you...

There we go, thats the finished
article, well sort of finished anyway. Some
trim around my dodgy dremel on blanking plate
skills will finish it off. Anyway, thats not
the point at the mo, its whats behind there
that counts...
What you
need (w/Maplin Codes):
1x Temperature Module
- FE33
1x Probe for above - FE34
1x Stripboard - JP51
2x BD139 Transistor - QF07
2x Power Relay - UQ94
2x 1N4001 Diode - QL73
4x Push To Make Switches of your choice (I used
FF96)
2x 330R Resistors - M330R
1x MALE Molex Connector - JW64
Various Wiring, Solder, Soldering Iron and the
usual mod tools :)

The display
What does
this circuit do?:
This circuit allows you
to set two temperature thresholds using the
switches on the front, a 'high' threshold and
a 'low' threshold. When the temperature detected
by the probe displayed on the LCD is below the
lower threshold the fans are completely off.
When the temperature is above the lower but
below the higher threshold the fans are at 5v
(or any other voltage you desire - explained
later). When the temperature is above both the
thresholds the fans are running at 12v. Thanks
to the temperature module, this circuit does
not switch the fans on and off rapidly, i.e.
the fan must stay on for a minimum of 30s before
being allowed to go off. The prevents them turning
on and off all the time which gets annoying.
Lets get
down to the modding... :)
Attaching
the new probe:
The module comes as standard with a sensor soldered
directly onto the PCB, but this isnt much use
for taking the temperature of a remote source,
i.e. the Graphics Card heatsink. Fortunatley
for us we ordered the extra probe didnt we?
;)

Heres the module with the extra probe

After unscrewing the battery holder via the
6 screws (3 down each side) we can see the original
sensor (circled).

The new sensor
All you have to do is unsolder
the old sensor from the board and solder the
leads from the new one onto the pads, it does
not matter which way round it goes.

Fire up the iron!!

Theres the new sensor attached no probs :)
Now its time to knock up the PCB
with all the goodies on and attach it to the
temperature module...
Building the circuit:
The following is
the schematic for this circuit, I know it isnt
particularly clear so if you have any questions
feel free to mail
me.

Ill just give you a quick explanation
of how it works...
Lets assume that the temperature
is inbetween the two temperature thresholds.
This means that both of the relays are in the
NC position (normally closed). This sets the
fan output at 5v.
If the temperature falls below
the lower threshold the temperature module sends
+1.5v from pin 7, this allows the transistor
to conduct and so the relay switches to prevent
any current from going to the output, hence
the fan goes off.
If the temperature rises above
the higher threshold the module sends +1.5v
from pin 6, this, again, allows the transistor
to conduct and the first relay switches. It
switches over so that it is giving 12v to the
second relay instead of the usual 5.
Now all you have to do is build
that schmatic onto your stripboard (you will
have enough if you ordered that number that
I gave you ;).

There's my board finished
Once you have built that circuit
its time to connect it to the actual temperature
module.
The Pinouts:
Pin Number |
Connection |
1
|
0v Rail |
2
|
Switch between pin 16 |
3
|
Switch between pin 16 |
4
|
None |
5
|
None |
6
|
Marked on schematic |
7
|
Marked on schematic |
8
|
None |
9
|
None |
10
|
None |
11
|
None |
12
|
Switch between pin 16 |
13
|
Switch between pin 16 |
14
|
Connect SPST here for C/F
switching |
15
|
None |
16
|
Connect switches 2,3,12 and
13 |
There, that should be enough information
for you to be able to complete the project.
All you have to do is mount it now, but ill
leave that up to you because we all have different
tastes ;).
Im currently working on a backlight
for it, and will probably be inverting the display
(like all my others ;) so you can look out for
those soon I think.
Once again, any problems just
mail me. |