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Forum Index : Electronics : PCBs U/V LEDs
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Dave Newbie  Joined: 01/02/2015 Location: New ZealandPosts: 5 |
Hi guys. Firstly let me say hello to all of you - I'm a great supporter of this type of forum; you just can't beat experience and it's great to have a place like-minded and creative people can gather to share their ideas and projects. I find it all very inspiring. I've just read the article on making PCB's. I've used my own flouro-lamp based exposure box for years now and it's getting a bit long in the tooth. The advantage of it is I know exactly how long to expose the (Kisten) board for; the disadvantage is that it takes about 10 minutes to expose a board and it is about time I got with the program and updated to U/V LEDs. I did a quick but of research a while back and ran out of steam with the idea and thought no more about it until I read Pete's article on making PCBs and he describes using his C&C U/V LED system to expose his boards. While that fancy and well-made rig is a little over the top for my simple needs, I would appreciate if someone who knows more about this sort of thing could post a diagram for a U/V LED driver board or similar as a starting point for me to convert my exposure box to use LEDs. My system is essentially a recycled flat-bed scanner (donated by one of my computer-repair company clients) with the guts removed and a couple of 300mm flouro tubes mounted in it long-ways with foil wrapped around the bottom and sides of the case for better light dispersion and reflection. I use a solid-state, transistor-based circuit with a hand-wound transformer to drive the lights and connect that to an interval timer with four pre-set times. As it turned out I only need one of those settings; the lights turn on with a momentary push of a micro-switch and the timer automatically turns the lamps off when the pre-set time is up. A reclaimed CPU fan runs to keep everything cool in the electronics bay. What I'd like to do is put an array of U/V LEDs in instead of the flouros and wire the driver of that to the timer. I'll obviously have to remove the flouro's, the inverter and any other components associated with those lamps and replace it with the LED equivalents as well as change the time(s) but that's a small matter of changing the values of a few resistors. If someone has a circuit for a suitable driver or a similar system I could check out for inspiration, I'd really appreciate seeing or reading about it. Thanks and all the best Dave Thompson, Christchurch, New Zealand. Dave T. Christchurch, New Zealand. |
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| Gordz Regular Member  Joined: 10/08/2013 Location: AustraliaPosts: 55 |
Hi Dave, there is nothing too special about using UV LEDs (constant current mode and series connection is optimum)except that you need to select the correct wavelength and power for your application. LED drivers are cheap and plentiful on Ebay if you don't want to cook your own. |
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Downwind Guru  Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Glade you like my article, im unsure how its over the top if you extract the basics for your needs. All you need is the general UV leds that is sold on ebay, its been a while so i dont recall the wave length, but i just used the standard ebay cheap UV leds. The important part is requiring about 100mm between leds and PCB to allow the light to spread wide enough or you will get dots and not full coverage. That is a problem with using a scanner, you need the 100mm distance, although easy to elevate the PCB above the scanner. There is another thread i done with converting and old bubble jet printer as a UV scanner should you do a search. EDIT...... Found it http://www.thebackshed.com/forum/forum_posts.asp?TID=2303 Pete. Sometimes it just works |
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| Dave Newbie Joined: 01/02/2015 Location: New ZealandPosts: 5 |
Hi Pete and Gordz and thanks for the replies. Pete, I meant over the top as far as C&C scanning etc, the basic information is excellent and what I was looking for. Also a good tip about keeping distance to avoid spotlighting - I'll keep that in mind. All the best, Dave T. Christchurch, New Zealand. |
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| Gordz Regular Member Joined: 10/08/2013 Location: AustraliaPosts: 55 |
Yes forgot to mention spacing. I would power an LED up and hold it over a sheet of paper to see the spread of the light to work out the spacing at the height. Cure power drops of sharply so test before final mounting and assembly. |
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