8 Channel software controlled fanbus with PWM – Path 4


The PCB measures approximately 37 x 119 mm, and is perfectly suited for the backside of a spare front bezel.



The PCB is a ”rough cut”, so you’ll have to **FILE** the edges for a perfect fit.

Mounting of the components

The PCB is pre-drilled with 1mm holes. The components must be mounted according to the layout below. Remember to mount transistors, rectifiers and capacitors in the right direction.


The PCB connectors can be quite difficult to mount, but if you heat them with the tip of the soldering iron, they can easily be pushed into the holes.

The mounting holes must be drilled with a 3mm drill.

The transistors generate almost no heat, thanks to the PWM technique. But the BD135 is not controlled by PWM, so a little piece of aluminium to cool it down is highly recommended. If you want to draw more than 300mA from the outputs, you should consider a little heat sink on each transistor.

The BD136 transistors can be mounted on the same piece of aluminium, but each transistor needs to be insulated from the aluminium. At the time these pictures was taken, heat sinks weren’t even thought of. Since then, I’ve cut small pieces of aluminium and mounted each piece on a transistor. Thermal compound isn’t needed. When all components are mounted, you get something like this:


Time for some wiring. For the parallel connection we’ll need the 8 data pins and STROBE. That makes a total of 9 wires. You could use a printer cable, cut one end, and solder the wires. But it would be nice to be able to take things apart without soldering, so we used a D-SUB printer connector, and a printer extension cord.


These wires should be thin, soft and around about 10 cm long. Solder one end to the connector, and the other end to the PCB’s connectors. Normally, the DSUB connector is numbered. If not, use the pin layout drawing as mentioned earlier.

Then we’ll add some wires to our blue control LED:


The remaining wires should be at a certain thickness. The outputs may conduct 1 Ampere at most, and the supply wires (12V and GND) 8 Ampere max.

For the outputs we’ve used standard mains wire. A wire thickness of 0,75 square millimetres is more than enough.

The supply wires should be at least 1,5 square millimetres, but it depends of the maximum current. For higher loads than 5 Ampere total, a wire of 2,5 square millimetres should be used.

A piece of red wire is soldered to the ”12V” connections on the PCB. The other end is connected to the 12V pin of a Molex-connector.

A row of terminal connectors is mounted with blue mains wire as shown:


We’ll only need 5 outputs, which explain the 5 x 2 terminals. Remember, the blue wire goes to every second terminal.

Solder the brown wires to the outputs. Connect them to the remaining holes in the terminal connector row.


By now you’ll have 2 loose ends of blue wire. One of them must be soldered to the PCB connector marked “GND”, and the other wire must be connected to one or both of the GND pins in the Molex connector.

It’s very important that you mount the pins correctly. Wrong orientation will short-circuit your power supply. Check with a already mounted connector from the computer. The black wire from the PCB goes to one or both black wires from the Molex-connector, and the red wire from the PCB goes to the yellow wire in the Molex-connector.

Now we’ll mount the override switch. Solder a wire to the connector on the PCB marked “12V via switch”, and after that a wire from the 12V connector. These 2 wires is soldered to a switch, which can handle the maximum load of all outputs.

For the same reason, the wires must be at least 1,5 square millimetres.


Now we’re ready for the first test. If you happen to have a hobby power supply of 12 volts, you can try the construction with that first. If all fuses are intact, and no smoke is emitted, you’re ready to connect the fanbus to your computer.

At first, leave the PCB on the outside; just connect the printer cable and power connector to the computer.

First try without any fans connected, and then connect a fan, one by one. Test each output via CKControl II to see that all fans spins right.

Leave the construction for 30 minutes or so. Touch the components, to tell whether they get to hot or not.

The 1W resistors should generate a little heat, which is perfectly normal.

If it seems to be fully operational, you’re ready to mount the fanbus in your computer.


Mounting the fanbus

There are a lot of possibilities regarding the physical placement of the fanbus. But since the PCB goes so well with the measures of a spare front bezel, we’ll be using that option here.

In general, the trick is to avoid contact between any components and the metal frame of the computer, or other hardware inside.

We’ll need to drill 4 holes in the front bezel. Two for the PCB itself, one for the switch, and one for the control LED. The switch hole’s size naturally depends on the switch used, but our switch was 6,5 millimetres. For the LED holder, we’ll need a 2,5 millimetre drill, and for the last two holes, a 3 millimetre should do fine.

It very important that you drill these holes with great accuracy, or the final result will look awful.

The case we used for this project is a Chieftec standard type, and to ease drilling, you can draw guidelines with an old fashioned pencil. Standard soft eraser can remove unwanted lines after drilling.

Now, let’s take some measures:


A measuring tool, a pencil, soft eraser and a pin needle is needed here.

Looking back, it’s a good idea so cover the bezel with masking tape. We didn’t, but after scratching 2 bezels, we decided to recommend this.

The following measurements are done on a Chieftec bezel, and it could vary from your own bezel.

First, find the middle, both horizontal and vertical, and draw the lines up. The distance between the mounting holes on the PCB is 62 millimetres, so you’ll draw a line 31 millimetres on the left and right side of the middle line.
Now measure down 16 millimetres from the top, towards the middle, and draw a horizontal line. By now, you should have the marking of the 2 holes where the lines crosses.
The holes for the LED and the switch should placed right underneath each other, and approximately 10 millimetres from the side should do fine, but remember to take the measures of your switch into consideration.

Having all holes marked up, you’ll now need to make a little hole with the needle pin. That prevents the drilling machine to loose grip.


With that done, fetch the drilling machine, and drill carefully.

The final outcome should look like this, if everything went right:


The LED holder must be ”clicked” in position, and the LED is mounted afterwards. It’s a tight fit, but when it clicks, it’s fixed perfectly.

The switch is screwed on using the included nut and washers. Now its time for this:


Two pcs. M3 screws, 2 nuts, and 2 plastic raisers. The raisers can only be bought in packages of 10-25 pieces, but a worn pencil can be taken apart and cut to nice little raisers.

Put the screws in the front bezel, put the raisers on the screws, then the PCB, and finally the nuts. Screw it all together, and we’re almost done! It’s a great idea to insulate the PCB and connectors to avoid shorts. Especially at the top, bottom, and around the printer DSUB connector.


Now it’s just to fit it all inside the computer. We’ve pulled wires from all fans to the front, so any mounting and dismounting will go smoothly.


Just before closing up, a final test is recommended to ensure that everything is connected properly.

And of course – everything worked. Nice, simple outer looks – advanced and powerful on the inside:

8 Channel software controlled fanbus with PWM   Path 4



As seen on the CKII picture above, all fans correspond to the CPU temperature. The first output controls a cold cathode light, and output 6 and 7, creates a little “flicker” lighting via 2 Lazer LED’s.


If you’re buying a commercial fanbus, it’s often hard to find a exactly match to your criteria. This fanbus offers 8 individual independent, software controlled PWM channels with 10W per channel. Furthermore, it’s 100% programmable – which makes you capable of creating output patterns to match your needs exactly. Fans, LED’s, cathode lights, relays for controlling the coffee machine… There are no limits to controlling your environment with CKII!

Control the relation between intake and exhaust in your computer system, finding the perfect settings for your own system. And via the MBM5 integration, no fan spins faster that needed!

One drawback is the occupation of the printer port – but most printers offers USB connection today. If not, a PCI extension card with an extra printer port can be bought.

You can buy the PCB used in this project. The price for the PCB is 31,00 EUR / 35,00 USD plus shipping. Contact us for more information.

The project:

We sincerely hope that this project will inspire you to new cool casemods and alternative uses of our beloved computers.
A 2.2 version is under consideration, and we have more cool projects coming up.

Have fun, creating your own CKII fanbus!

© d_morten / Deep Thought

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