I had ordered
http://www.ebay.com/itm/221248115201?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649and this should match my photoresist. They are marked as peak
sensitivity at 400nm. So this led should bje just right (and blueray
laser at 405 too)
Will check...
On 09/18/2013 01:06 PM, Robin Whittle wrote:
> A further correction . . . The LED I bought was advertised
>
> http://www.ebay.com/itm/120896174810
>
> as:
>
> 380 to 385nm
> 1000mA
> 9 to 11V
> 900 to 1100mW output
>
> actually has a peak output at 394nm. I measured it with a monochromator
> from an old spectrometer. The monochromator reads correctly within 1nm
> for both a 532nm green laser and for the 404.7nm mercury emission line,
> so I think my reading is reasonably accurate. Half power was +/- 6nm.
>
> When I wrote my first message I thought this was probably the same as an
> identical-looking device for which there is a little more data:
>
>
> http://www.leds-global.com/ultra-violet-380nm-high-power-led-modules-p-7.html
>
> 375 to 385nm
> 1050mA
> 10 to 12V
> 400 to 500mW output
>
> However, there is a serious mismatch in the specified output.
>
> This LED runs at almost 10 volts with 1 amp, which matches the eBay
> specification exactly, but would be at the low end of the range for the
> p-7 device above. The shorter the wavelength the higher the voltage, so
> this is consistent with the eBay specification being for a LED with a
> longer wavelength than "380 to 385nm".
>
> I think the eBay LED is a closer match for this one:
>
> http://www.leds-global.com/uv-10w-390395nm-high-power-led-p-146.html
>
> 390 +/- 5nm
> 1050mA
> 9 to 10V
> 800 to 1000mW
>
> I don't have a chart for the wavelength sensitivity of Riston - I was
> referring to:
>
>
> http://www2.dupont.com/Imaging_Materials/en_US/assets/downloads/datasheets/mm500series.pdf
>
> which states that the "peak response" of the material is 350nm
> (nanometre) to 380nm.
>
> I was keen to get a high powered LED with as short a wavelength as possible.
>
> While I may have paid more than I needed to for a 395nm LED, the good
> news is that Riston seems to respond just fine to 394nm.
>
> Searching eBay for UV LED 10W 395nm I find various cheaper LEDs, but
> 395nm is not their center wavelength - they are typically 395 to 405.
>
> There are likely to be uncertainties regarding the actual wavelength of
> LEDs vs. how eBay seller advertise them. However, if a 3 minute
> exposure is OK at 30cm, which is fine for small PCBs, then I think a 3W
> 390 to 395nm LED would be a good, inexpensive, choice.
>
> For instance, this supposedly 3W 390 to 395nm LED:
>
>
> http://www.ledfedy.com/products/1-500w-led/3w-led/3w-uv-led-390-395nm-double-chips-with-star-pcb-1492.html
>
> costs USD$4.69 - not counting postage.
>
> A LED like this would be easy to run - just get a 12 regulated power
> supply and choose a resistor which drops (12 - 3.3) volts at 0.7A = 12
> ohms. The LED would need a heatsink and the resistor would dissipate
> about 6 watts.
>
> - Robin
>
>
>
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