Re: Light for a gun safe

John Woodgate wrote:

I read in sci.electronics.design that John Smith <bill.gates@xxxxxxxxxxxxx> wrote (in <d3dfbd$7jp$1@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx>) about 'Light for a gun safe', on Mon, 11 Apr 2005:


"Chris W" <1qazse4@xxxxxxx> wrote in message
news:OZp6e.268$yO2.130@xxxxxxxxxxxxx

I want to put a light in my gun safe that will come one when I open the
door. Since running power into the safe is more than I want to deal
with, it will have to be battery powered, I was thinking 2 to 4 AA
alkalines. Four LEDs should give me the amount of light I want. I also
want an automatic dimming, where the darker it is in the room the
dimmer the LEDs will be. Since this is going to run on batteries, I
want it to be as efficient as it can be. I went looking at data sheets
and found this,

http://www.catalyst-semiconductor.com/documents/32.pdf

I was thinking of putting a photo cell in parallel with a pot to get the
value for Rset right Does this sound like a good plan or does someone
have a better suggestion? I am just getting into electronics as a hobby
so I'm not too familiar with what all is out there, I mostly just look
through the Mouser and Digikey catalogs.

Also it is my understanding that they are making LED's more efficient
all the time, can some one give me a good source for some of the newest
most efficient LED's?  I only need 4 for this project, but I have
another project that will need a lot (around 100) and I don't want to
spend more than I have to.  Also, both run on batteries, so the more
lumens per watt the better.  Specifically I am looking for 5mm white,
red and green with a viewing angle of 45 to 60 degrees with maybe some
of the whites having a viewing angle of 30 degrees.

--
Chris W

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Try this:
http://www.technologystudent.com/elec1/ldr1.htm


With your chosen device, what were you going to do with SHDN (the PWM
input)?


He says he wants to use it for dimming, using a photocell and a resistor. But the impedances are wrong for a CdS cell. He will need to add at least a transistor (a FET would be indicated, because of the high impedance of the CdS cell at low light levels) and associated resistors to do that.

How would I hook up the transistor to that chip? Can you recommend any part numbers with data sheets I can look at?

--
Chris W

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