# How to get a 1.6 times higher supply voltage

I trying to build a UV exposure box so I can do my own PCB at home. The problem is I don't have a power brick that can output 32V @ 1A. the matrix consists of 10 columns $\times$ 10 rows.

The power brick am using is 20V @ 4A. Be much easier to buy one but I thought this might be good exercise to do.

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Where are your current-limiting (and sharing) resistors? –  Connor Wolf May 28 '12 at 9:40
@Fake - they were out of stock. –  stevenvh May 28 '12 at 12:57
Why not just build a Constant current driver. That is the way led are driven these days. –  user10030 May 29 '12 at 18:51
@Richard - I see this was an answer first, and you're lucky, because I would have downvoted it :-). A constant current driver doesn't answer OP's question. You'll still have to deal with a supply voltage, and the 20V still isn't sufficient. You also don't explain what to do with the 10 parallel branches. The upvote for your comment is ridiculous. –  stevenvh May 30 '12 at 4:11
@kevlar1818: What's hostile about a downvote if the answer is no good? With a constant current driver alone the circuit won't work! 20 V isn't enough. Also just applying 1A from a constant current source won't guarantee that all branches get the same current. This would have been a bad answer, and now is a bad comment. –  Federico Russo Jun 13 '12 at 5:23
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If the current is 100mA (you talk about 1A for 10 strings) R would be 40$\Omega$. Make that 1W resistors. Total power is 20V $\times$ 20 LED-strings $\times$ 100mA = 40W.