I wondered if I could run a little project by you folks and try and get some feedback on how I'm going to do it?
First a bit of back-ground on what I'm up to:
A few years back when I was working in the dairy industry as a technician, I was sent to a job in a 10 year old dairy shed that had electronic cup-removers on each of the 40 bales.
What bought me to the job was that the owner of the shed had had a bit of a muck around with the electrical systems under the rotary platform and had cooked the circuit boards in all of the cup-remover units, by putting 230VAC through what should have been a 24V DC system
I ended up replacing all of the boards in each unit and on each unit is a 10mm dual colour LED, to indicate various states of operation and programming status.
Being the sort of guy that doesn't like to see anything go to waste, I asked the guy if I could please keep the LED's for my own use, he said no worries.
Jump forward to now, I've had these LED's sitting in one of my draws here in the workshop and a bit of an epiphany struck me the other night.
I have the idea of making some sort of a lighting source for use in here at night when I'm operating my ham gear.
Making up some sort of a mount for the LED's is not a problem at all, what is troubling me is how am I going to power this.
I got one of the LED's and hooked it up (with no current limiting resistor, I might add) and something sounds a bit strange about the current draw results I got.
With the Red PN junction connected, I got a current draw of 230mA @ 3VDC.
With the Yellow PN junction connected, I got just over 100mA @ 3VDC.
These measurements were taken with a FET driven analouge meter.
I also tried a variable resistor in series with the LED on both junctions and while the brightness more or less fell off very quickly (almost exponentially), the current draw between full brightness and quite dim only reduced by about 40-50mA.
Now, if I am to use 30 of these LED's, we are talking quite a bit of current, 7 amps on Red and 3 amps on Yellow.
See folks, this is what I'm on about, if it was a common voltage, it wouldn't be an issue, but 3V power supplies are few and far between, especially at this sort of current capacity and also having (reasonably smooth) DC output.
Had this been a few years ago, I would probably have wound up a custom transformer, however, I've now run out of bits to make a decent transformer.
Any and all input will be taken into account, there is never any such thing as a silly idea when you are designing something.