Looking for the simplest way to use a portable 5 volt USB power pack with a PC case fan. I already have a 90mm PWM Noctua (NF-A9 PWM) that’s be nice to use, but can swap out if necessary. Use case is for a filtered forced air feed for a face mask. Ideally I’d like some control over fan speed (off, low, high is fine).
Simple is best! Unless it is an OTS sub $5 part that is all inclusive, I don’t want to start soldering up resistors, capacitors, etc.
Doable, or pipe dream?
Not 100% sure I follow, but I did this to the case fan sitting on my desk, and run it off USB…
I’m not saying it’s 100% most efficient use of parts, but both were destined for the bin, and now blow a breeze at my face whenever I want (well, when I’m not WFH)…
Most case fans are 12 volts and USB is 5 volts. To run at full speed you’d need a buck boost converter. You could buy one and solder it up or there are some mass produced solutions like this where it’s built into the USB connector housing.
Noctua also makes an NF-A9 5v to avoid the boost converter. You could just hook power straight from a USB cable to the fan, but you won’t get any speed control.
Could I put a pot in the line to get speed control?
You’re probably going to want a squirrel cage or rotary vane type fan if you’re working against a filter. Regular computer fans don’t make a lot of pressure.
I’ve seen somewhere a 3D printable vane fan intended for respirator / ventilator applications. You might look into those.
You need pwm instead of a pot
I bought a USB-powered fan to use with my Monoprice Mini Delta printer (which lacked a fan for the board), so they are available.
Here’s a link:
Gdstime 60mm x 60mm x 10mm 6CM USB Power DC 5 Volt Brushlee Cooling Fan https://www.amazon.com/dp/B01CU55HLO/ref=cm_sw_r_cp_apip_AaIMvvcqUAw6t
It would require some simple circuitry but you could set up a 3-way switch for off, PWM, and full on. You could build a 555-based PWM or find one on EBay/Amazon. A quick search found a PWM circuit for cheap(ish) on EBay. It’s late so I won’t vouch for this one, but something like this should work.
Would it make sense to use a cordless drill battery pack, like an 18 volt which many make 5v usb outlets? Maybe create a PWM module for it.