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| Project Jetsam: Bartop speed build using 100% recycled materials [Completed!] |
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| jeremymtc:
--- Quote from: Zebidee on March 03, 2024, 01:23:56 am ---Might be easy enough to hack into the laptop's 12v rail. If you put in some small discrete holes at the top/back to let the warm air out, convection currents might even be sufficient. I like to cover holes with some scrap nylon mosquito meshing to keep pests out. I was just now thinking - I've got one of those laptop cooler bases that plugs into USB. Two big slow fans that go underneath. It came free with a laptop but I never use it, even in a tropical climate. It could be perfect for this kind of bartop. --- End quote --- Excellent points, all! Thanks. I had realized after posting that wiring to the PC power supply would be a non-starter since a fan would be 'always on', so sourcing 12V somewhere on the mobo might be a better path forward. Likewise had thought the same about just positioning vents above and below the motherboard carrier might allow for some additional convective cooling without a fan. I think that anything I do is basically "insurance", as there was no active or passive cooling aside from the heatspreader in the original PC product... and tangentially that might explain why the usb port headers were flaking out, and why my having reflowed them brought them back to life. A USB laptop cooling pad is a great idea! |
| firedance:
Good shout on the usb cooling pad, I used some of the fans from one on one of my bartops, can't remember which one tho ;D |
| Ond:
I love projects built from recycled parts! Cardboard template and speed built in scrap plywood. The de-cased PC speakers are useful for projects. I think I have a tub with similar parts I dig into now and then. For fan or cooler control you can take 5V from a USB port and use a relay to switch fans off when powering down. Some USB ports stay powered on if there is power connected to the motherboard though, and some can be toggled in bios to drop the 5V on power down. You can power a 5V fan directly from USB, but I think its better to take 12V from somewhere else and use a relay. |
| Zebidee:
You won't need a relay for the fan if the 12v rail is being switched on/off by the laptop mobo anyway. 12v gives you more flexibility with fan choice than 5v. Then, if desired, you can lower the voltage/fan speed by putting a resistor in series, which both limits current and reduces voltage. Exact specs for the resistor depend on your fan and desired voltage, but a little experimentation and application of Ohm's law helps. You probably want the fan voltage to be at least 8v or so. I have some 3W rated resistors I use for this kind-of thing, though 1W would probably be sufficient. You could use a pot to control fan speed, but seems complicated and unnecessary. Maybe just until you work out the resistance value that works for you. If you are lucky enough to be able to source the fan voltage from an unused motherboard fan header, there may be a third pin to control fan speed, which could be controlled by software. These use a microcontroller to turn the fan on/off many time each second, and are more energy efficient than a resistor (which will dissipate some current as heat). |
| Ond:
Sure, if you can access 12 V on the board job done, too easy. I've used resistors on fans to bring the speed (and noise) down. No sense in running a 12V fan flat knacker if you don't need to. Specially some old dusty one you've ratted from a clunker PC ;) |
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