AuxFanControler, a New Revision

As part of my AuxPower1U project, I already build a stand-alone 4-channel fan controller. And it works perfectly even now. But I did notice some issues when trying to use it as part of other projects.

The first issue was it belonging to AuxPower1U Git repository. There was nothing wrong with that but, since I used it for other projects too, it seemed right for it to get own repo. And its own repo it got. While I will keep it compatible with AuxPower1U, each can change separately.

The second issue was its dimensions. Even though I would argue you cannot get 4-channel fan controller with those connectors in much less space, reality was that vertical mounting was impossible in 1U chassis. Not only that its sideway power entry made wire routing particularly bad in vertical scenarios but it also meant that total height was cutting it close for even 2U case. Reducing the PCB height was an obvious choice and while trying to figure out the layout, I decided to drop one fan connector. This allowed me to reduce size from 69x15mm to more reasonable 42x15mm. Just barely fitting 1U if we ignore sideway cable entry. And ignore it we can because I also adjusted connector to allow for mounting either vertical or horizontal connector. Yes, you will have one footprint unpopulated but that’s a small price to pay.

A third, minor issue was that board was hard to mount. For this I intentionally left back front side empty and with a bit wider side margins. This allows one to create slot in plastic and thus keep the board embedded with friction alone or, if needed, with just a touch of plastic. How that mounting looks like you can see on example of the new AuxPower1U board (that I’ll cover a bit later due to scheduling carfufle). Board sits between 2 fans and goes nowhere once slotted in.

I got PCBs from PCBWay and it arrived quite quickly. More importantly, its edges arrived cleanly cut. This is not something one notices unless they deal with some other PCB providers. I love OSHPark but them leaving tabs in place drives me crazy. Every time I get their boards, I have to spend minute or so per board filing those tabs down and it’s never fully straight edge. With PCBWay at least that task is of my back.

Also, compared to OSHPark they have way wider color selection. You can chose green, red, yellow, blue, white, or black for the same price. This allows you to distinguish boards at a glance. For this order I opted for the yellow soldermask which is not my favorite when it comes to reading slikscreen but it is rather nice otherwise. If silkscreen legibility is at premium, either red or blue are better choice. But that is the beauty of choice. You can find what works for you in any particular scenario.

Premium colors like purple, matte black, and matte green do come at a greate cost. However, they do ocassionally get a discount so its worth checking them out from time to time. For example, purple is going to be available at standard $5 price in September so you might want to check it out. Speaking of discounts, 3D printed TPU will be heavily discounted in September too so you might want to check it out. As somebody who printed TPU, I can only recommend you get somebody else to do it. :)

Soldering this PCB was a bit more difficult as compared to the revision A because components were a bit more pushed together. But that’s just relatively speaking - I am still using rather generous pad size so it should be easily doable.

Profile is similar to before but with a bit more agressive curve between 60-70 °C. This is something I plan to make configurable eventually but I don’t really have reason to do so right now.

Startup sequence is still powering fan at a time with a quick spin-up to 100% before settling down. Firmware itself still behaves as if it has 4 channels which makes firmware the same between revision A and B.

It’s just a small update but form factor change alone will allow me to use it in way more places that require stand-alone fan control.