Light proof ventilation

[ajs]

This is a bit of an out there issue for a forum such as this but if I asked in my usual places for something like this I'd get the response "don't use wood".

Background to this is I want to build an enclosure to house a device that holds a UV-C bulb to erase older computer chips. These chips are essentially obsolete, I have only occasional need for it so don't want to invest too much of either time or money. To give some idea a commercial unit comes in at around £100, I don't expect to match that costing in my time but it does put an upper limit on what I'd invest in it.

I need an internal volume of about a 4" or 5" cube housing a 3W bulb. Over a period of perhaps half an hour that's enough to get quite toasty without venting. The issue is that UV-C is quite nasty stuff, it is an extreme danger to eyesight and often used for its germicidal properties as it will damage DNA.

So, how to vent the box without letting the light out, at least not before it has be reflected several times? I  could put a fan in there, price there isn't an issue as I'll have plenty suitable in the scrap pile, but I'd rather stick to natural convection if possible, but any system of baffles I come up would either be a b*tch to make or add considerably to the overall size.

I don't know, I suppose I'm just asking if anyone has any immediate moment of inspiration.

 

[Fitzroy]

Workout the heat generation and the how big a heat sink (lump of metal) you would need to soak it up with an acceptable heat rise, make the enclosure big enough to hold also contain the heat sink.

 

[mwinfrance]

Lidl sell / sold such a box, began during covid ( we have one for phones and keys, due to SWMBO's job ) cost about €15.oo , uses a plastic housing and "bathes" the phone or "whatever" in UVc, gets a bit warm if you forget and leave the phone in for longer than the recommended 15 minutes, but not hot enough to melt the plastic. Been running it for two years now, every day, 15 minutes ( or an hour if we forget ).Box made from ABS should do fine, if you really are worried put a couple of internal baffles at each end to block light leaks and drill holes in the corresponding ends of the outer casing , one at bottom, one at top to get cross flow.
I just had a look at ours..no vent holes.

 

[Spectric]

I do recall those windowed eproms where UV to erase, put it into a programer and then once programed you put a sticker over the window. Where I worked in those days we had a lot of them and they were small black boxes with just a tray, they only worked once the tray was fully in to prevent light escape and I cannot recall them being ventilated. You are really going back into the dark ages as these were before the electrically erasable EEPROMS.

A shame this was not asked about 8 months ago as I had been having a sort out and amongst the stuff I did not remember still having was a handheld programer in a leather case, two erasers and several trays of new eproms that along with some ancient test gear all went to be recycled, never thought anyone would be even remembering that old technology as nand flash was so much easier. Why are you still using them, is it an old computer like a Z80 or an old ECU like the EEC 1v or ECC V ?

 

[Sideways]

My ideas would be to construct a box with a very simple labyrinth on the inlet and outlet and have both of those open to the outside on the base of the unit so you get another stage "for free" thanks to the tabletop beneath.

I doubt UV will reflect around the baffles if you paint the inside "black".

Alternately, something based on two 180 degree bends of say 40mm pipe and just use a little 40mm computer fan. Better airflow around curves....

 

[mwinfrance]

I've looked at our box ( UVc mentioned above )..Made by a company called Beldray..out of China ( doesn't say PRC, but probably is )..Distributed by a company called Global Sourcing

Item Ref is EE6027B2LDLDIR
210327
UP GLOBAL SOURCING UK LTD
MANCHESTER OL9 0DD
GERMANY 51149 KOLN

Might save you having to make one if you get in touch with them, maybe they'll sell you one.
Runs via USB..Marked Input 5V ... 2A
HTH Mike

Totally light proof, no leakage at all..power indicator on lid, on /off switch on right lower corner of lid.
ours is White L 19cm W 10cm D 5cm ..interior space easily takes my OPPO A94 5G..I could probably stack 4 of them in there.

 

[HamsterJam]

Workout the heat generation and the how big a heat sink (lump of metal) you would need to soak it up with an acceptable heat rise, make the enclosure big enough to hold also contain the heat sink.

This is what I’d be thinking - bolt two heatsinks back to back with a smear of thermal conductive paste between them. Position one inside and one outside the box.
Alternatively can you make a labyrinth/baffles by putting two heatsinks front to front with the fins interlocking but not touching?

 

[paulrbarnard]

They are available new on eBay for £15 and on Alexpress for £6.

 

[ajs]

They are available new on eBay for £15 and on Alexpress for £6.

With truly shocking standards of electrical safety. I've seens tear downs of them, bu the time they are safe you are almost rebuilding from scratch. I'd also liek to to use the bulb I've slected as readily available.

 

[ajs]

I do recall those windowed eproms where UV to erase, put it into a programer and then once programed you put a sticker over the window. Where I worked in those days we had a lot of them and they were small black boxes with just a tray, they only worked once the tray was fully in to prevent light escape and I cannot recall them being ventilated. You are really going back into the dark ages as these were before the electrically erasable EEPROMS.

A shame this was not asked about 8 months ago as I had been having a sort out and amongst the stuff I did not remember still having was a handheld programer in a leather case, two erasers and several trays of new eproms that along with some ancient test gear all went to be recycled, never thought anyone would be even remembering that old technology as nand flash was so much easier. Why are you still using them, is it an old computer like a Z80 or an old ECU like the EEC 1v or ECC V ?

Yes it's primarily legacy stuff, like I said it's only a fringe requirment. If it was a lot I'd spring the money for a commerical unit.

 

[Spectric]

Yes it's primarily legacy stuff, like I said it's only a fringe requirment.

What is the application ?

 

[Jameshow]

How about a chimney type vent going out the roof or window, this would create quite a draw and the UVc light would be dissipated into the atmosphere.

 

[ajs]

What is the application ?

Whatever comes in. Primarily collectors/retro stuff where ideally you want to keep as much original as possible. Some of the early EEPROMs were almost drop in replacements but power consumption tended to be quite a bit higher.