I've observed that all the "UV" LEDs that I buy glow what looks like purple to me. Is this me, or are they not actually UV? They don't actually confess what their wavelength is; what is the typical wavelength of LEDs that claim to be UV?
And the money question: Are they the ones you would use for PCB exposure? (e.g. GC Chemicals cat No 660 etc.)
I used one 15W UV lamp (type F15T8-BL) for years. Exposure distance was about 10 cm and time 15 minutes. Different brands of boards will vary. My current box has 3 tubes set a little higher, as I wanted a broader exposure area. Time is now about 10 minutes.
Re: testing UV output. Calciflor white is a very common whitener. If you have a white shirt done at a laundry, it probably has that whitener or something similar on it. Under near UV, it will look very bright white in a darkened room.
I've observed that all the "UV" LEDs that I buy glow what looks like purple to me. Is this me, or are they not actually UV? They don't actually confess what their wavelength is; what is the typical wavelength of LEDs that claim to be UV?
And the money question: Are they the ones you would use for PCB exposure? (e.g. GC Chemicals cat No 660 etc.)
I think it is normal for the light to be purple, I used to work for a printers as a press operator and often made my own plates (ie when I wanted them to be more accurate that the bosses so called accurate +-5mm ) and the UV exsposure unit had a 2 KW uv lamp, this was actuaslly quite a visible purple light, while it was obviosly not 2 Kw worth of visible light, the visible component was perhaps equivalent to 60 W
You might find this proect an interesting alternative to the expensive uv tubes and chokes - the leds are available from a couple of uk web base suppliers Phenoptrix or GoodWillSales.
thanks thats a good pdf, to be honest i think that the cheapest are the ones on ebay from china, now yea i poo hoo chinese quality too (especially in my professional capacity of QC inspector) but where the hec do you think your uk suppliers get them RS included who then sell them for the bounty of £ 2+ each ? I have ordered 250 for a tenner. I'll give them a bash when they arrive and let the forum know if they are crap but the specs are better than motre exspensive ones detailed from the suppliers you mention. of course the final word is quality and price and quality do not always go hand in hand