From the days when my computer was more to me than just a daily tool and was an overclocked monster I have been looking for a versatile, affordable fan controller. In pc-land it is generally a balance of cooling power and noise, I was looking for a way to break that cycle – and provide an opportunity to print a circuit board.
All the new online small-batch circuit manufacturing was intriguing and thus I took the desire for a fan controller, coupled it with wanting to hold in my hand something I designed on a computer and this is where I ended up with:
This is actually two circuits on the same board. The ‘cheap’ bundle order was based on this size boards so i drew them up in ExpressPCB using the default size and found I could fit two per board. The schematic and layouts are here. The brains of the operation is a TC649 from Microchip. It is designed for use in servers and other electronics as a fan controller and it has all the goodies:
- PWM Based
- Speed detection – using only a two wire fan!
- Stall protection
What the above means is the chip can sense the speed of the fan and can adjust it’s speed based on the temperature detected by temperature probes (thermistors) I have remotely in the top of my cabinet. What sometimes happens when the fan is going too slow (low temperature) it will ‘stall’, or stop turning. This chip can detect that and bring the power up to 100% for just long enough to get it spinning again. Pretty handy chip.. and you can get them for free for onesey-twosey type stuff. They offer samples on their site!
This particular one is in the cabinet for my home theater equipment driving two 8″ fans – one in the top of the cabinet and one in the bottom. The wires in the center carry over the power (12v/5v/ground) from the left side to the right, so I only used one regulator. In the future I would probably put traces there for that job that could be cut if the board was separated. One update I had to make for the very large fans is moving to larger power transistors. I scavenged some from a broken power supply, complete with heat sink! The picture below shows the configuration which has been running for over a year.
And the remote thermistor probes at the top of the cabinet shown below. Wired with cat5 of course :)