Messing around with some QX5252f (the IC that drives LEDs with one AA battery)

rngwn · 2019-07-27T09:13:10.000Z

I have been trying so long to find myself a neat way to drive a 5mm LED with single AA battery. After several years, I stumbled upon the QX5252f that can do exactly just that with one extra inductor. Well, I know that this IC has been out there for quite some time, but it's exciting to experience it first-hand.

Here is the protoype:

The schematics I used is the typical one I found on the internet (sans the solar cell). One of these are shown here:

The LEDs used in this prototype. It's supposed to be able to handle more current than the standard 5mm ones. The actual specs for these types are all over the places, however.

The setup in action.

I swapped out the 47 uH inductor to 33 uH for more LED drive current (in the image above: 70ma from 1.5v source).

The circuit could easily be converted into the "emergency light" that lights up at the loss of the mains power. All I need to do is probably to use 3v mains adapter in place of the Solar Cell and add the Ni-MH battery. I might experiment more on this later on.

Barkuti · 2019-07-28T02:00:44.000Z

You should also test stuff in the worst possible conditions, like for example the output voltage from a depleted Ni-MH or alkaline cell: 0.8 - 0.9V.

Cheers :-)

Lightbringer · 2019-07-28T02:27:19.000Z

My bobofett light (Inland R22) uses a similar IC and will draw down to 0.5V or less from an alkaleak. It needs higher voltage to start, though, but once it’s going it’ll wring out every bit of juice and pulp that it can.

Output gets dimmer and dimmer as voltage drops, of course, but it’s still hella interesting and useful.

With a LFP cell, it’s quite nice and bright. I wouldn’t try it with a fully-charged Li-ion, though.

rngwn · 2019-07-28T02:31:52.000Z

I did tested 0.8v with the PSU. That’s when the current start plummeting. The interesting find is that once the IC stops pulling current, it doesn’t turn back on even when I ramped the voltage back up to 1.5v.

Since I have like 50 of these, I plan to do stupid things with some of these. Example would be trying to run these in parallel.