Got round to sorting this out. I was going to print an enclosure with some 80mm fans in but I didn't want to go to a load of effort and find it didn't work properly so I came up with something a bit more suitable for the job.
I cobbled together a 100mm extractor fan and some 100mm ducting. I was going to print a hood for for it but I found a dust collector hood on ebay which was near the right size so wasn't worth my time designing/printing. I bought an articulated mobile phone mount and printed an adapter to fit it to the hood. This provides 5 axis of adjustment and can be positioned/reach anywhere on my desk.
One problem I had when using the old extractor was that I got a lot of shadow/loss of light due to the tube etc blocking the light source. This was going to be even more of an issue with a large hood so I added some 5V LED strips fitted to some printed recessed mounts inside the hood.
I added a JST XH connector so it can be disassembled easily if required. I also wanted to be able to turn the fan on/off from the hood so I added switches for the fan and LEDs
Luckily there were already three ~12mm square cutouts in the side of the hood which just happened to fit some small SPST rocker switches I had. I printed some blanking plates to plug the remaining cutout and gaps.
It didn't seem like a good idea to run ~230vAC near the hood though so I used a 5v relay instead. The sleeved 5vDC wires travel up the ducting and then exit out the side of the fan and then into the box on top.
I didn't have room to fit the relay inside the box so I've fitted it to the top. I just need to make a cover for it as there are bare 230vAC terminals currently.
The box on top of the fan contains the timer circuit as this is where you would set the 'run on time' if connected to your bathroom lights. There was a fair bit of space in here and actually just the right amount of space to fit a decased 5v 2A PSU I had in a box of random PSUs. Switch live is connected to live so it will just turn on and off with the relay, no run on time required.
1st test:
It's all a bit McGuyver but it does work really well.
Parts list in case anyone's interested:
100mm In Line Bathroom Extractor fan
£42.99
Hon&Guan 4inch Aluminium PVC Ventilation Air Ducting Flexible Hose 100mm with 2 Clamps
£15.29
4 inch Hose Clips, HG Power Adjustable Hose Clamps 60-100mm
£3.99
DUBEUYEW DC 5V Relay Module 1-Channel Relay Switch with Optocoupler Isolation High/Low Level Trigger(3PCS)
£6.20 / 3 = £2.07
LED Strip Lights,USB TV Backlight 6.56ft/2m LED Lights for 40~60in HDTV,Waterproof SMD 3528 5V Daylight White
£6.99
FAPPEN Cell Phone Holder, Phone Holder for Bed Desk, 360° Flexible Articulating Long Arm Clamp Bracket Mount Stand
£14.99
POWERTEC 70169 Mini Gulp Dust Hood Collector with 4" ID Port
£12.20
SPST Rockers x2 - Already had
Total = £98.52