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We're running an exhibition that uses lots of 1.5V battery LED torches, which will be on for long periods, and their high-brightness means that using batteries is problematic (continual replacement). I'd like to use a PSU to power them, but don't want to have multiple supplies (or at least, I want to minimise the number of supplies used).

Is there an IC/circuit that can take as input, say, a 12V high-current dc supply, and present as output multiple independent 1.5V sources (each drawing approx 0.7A)?

I can't simply chain the torches I've been given in series, because each one has integral circuitry to run in full/dim/flashing mode according to button pressses, and in series they get very confused...

I even considered buying in my own high-brightness LEDs instead, but the torches (with lenses off) produce very sharp images -- they're being used to project shadow patterns in a gallery -- and so far I haven't been able to find a workable substitute. (It's bad enough, incidentally, trying to find a high-current 1.5V supply!)

I searched for similar questions, but none seemed to match exactly what I was looking for.

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  • \$\begingroup\$ Youu could try a reasonably high power supply and parallel the torches. You may need to get a post-regulator though. \$\endgroup\$ – Peter Smith Apr 8 '17 at 15:43
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    \$\begingroup\$ An exhibition sounds like long wiring to me. Perhaps consider a small custom buck converter (such as, but not necessarily, the TPS62510) for 1.5 V at each one or two LED locations. Alternately, something with higher current capability if more LEDs are nearby each other with short wiring. But either way using a higher voltage distribution system. But perhaps I'm thinking this is large when it's smaller than I'm imagining. So, off-hand, how many of these LED devices are you planning? How much wiring? \$\endgroup\$ – jonk Apr 8 '17 at 16:58
  • \$\begingroup\$ How many is "a lot"? How much do they cost each? Buy more and don't waste your time is my gut-opinion. \$\endgroup\$ – Andy aka Apr 8 '17 at 18:42
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FYI Many proprietary LED lighting systems I've seen use 24v DC supplies to distribute power; low enough voltage to be safe, high enough to provide sufficiently efficient transmission without needing excessively thick cables. However, it's all relative: practically, it has an upper limit on what it can power before using mains voltage makes more sense.

As Jonk suggested, use buck converters, one for each set of LEDs. Ebay has many such modules for $1- $2 each that you could use. I just searched for "buck module adjustable" and searched by ascending price, and for $1 inc postage found one that accepts input of 4v-35v and output adjustable 1.25v to 30v. (Maximum input current 3A, I presume this should suffice), it is based on the LM2596 IC.

Using this approach has a major advantage: long wires are unlikely to be of concern: each buck module will happily take less than the 12v (reduced by cable losses) and maintain your preset output voltage). If not, simply use a higher supply voltage, say 24v, thicker wiring where necessary - but for safety reasons, consider heat produced by the wiring (and everything else). Installations may be legally required to be installed by an electrician; even low voltages, partly for this reason).

At the same time, PSUs (wall warts) are so cheap, I'd have recommended you just buy one for each LED unit assuming nearby sockets - except getting ones with 1.5v output is rare AFAIK and might incur a premium. But since you seem willing to consider various alternatives, and time less critical than other factors, I would suggest, as an alternative to my above suggested solution that you reconsider alternatives to the torches; they don't seem compellingly compatible with your overall requirements.

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