Exposure box for alternative photography

Discussion in 'General Electronics Chat' started by bainsk8, Apr 14, 2012.

  1. bainsk8

    Thread Starter New Member

    May 31, 2011
    25
    0
    Hi all, I am planing on making said exposure box in the post title.

    So far I have created a digital count down timer using PIC 16F690 which when reaches zero (0) will knock off power, (240v AC supply) via a solid state relay to the UV lamps.

    My idea was to modify a sun lamp to incorporate the timer and relay, all of which I have at hand.

    My question is 240v AC will enter the sun lamp unit and obviously the digital timer is powered by 5vdc. Could and would it be safe to use an old switching power adaptor to power the timer and relay? Would it be also wise to put a 1amp fuse on the positive side of the 240v supply before feeding the said switching power adaptor and the UV lamps? Are there any other things I need to consider to make this a safe unit?

    I hope it makes sense of what I would like to do, if not I will try my best to draw it and post it up.

    Best wishes
    Darron
     
  2. bainsk8

    Thread Starter New Member

    May 31, 2011
    25
    0
    I take it that 188 hits and no replies must mean that what I propose to do above is safe??
     
  3. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,770
    970
    Why a 1 Amp fuse..seems low but I have no idea if your "sun lamp" is a 400W bulb or a 5W bulb? What is the rating of the sun lamp/ballast?

    As for using a typical wall wart to power your electronics side of the project thats fine assuming the power adaptor is regulated.. If not 5V might not be 5V (7V or more even)..
    Many people use an unregulated power supply and then place a typical voltage regulator (like a LM7805 or similar) with its associated components on the circuit board to provide a fixed/regulated 5V supply to the micro.

    As long as you keep the 240V isolated from your pic/timer side (via the SSR) all "should" be fine. Be safe
     
    bainsk8 likes this.
  4. bainsk8

    Thread Starter New Member

    May 31, 2011
    25
    0
    Thank you for your reply. The lamps are 4 x 15 watts and I thought a 1amp fuse should be enough not to blow unnecessary but to give protection against a surge. That said I did not consider the ballast rating as they do draw extra current on start up, thank you for drawing this to my attention.

    The wall wart is regulated at 12v which I plan to use for a fan to keep things cool and also fix/regulate 5v from it for the timer.

    Thank you again for your help, it is mostly appreciated.
     
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