Shopping in Aldi, Hexham on Friday spotted their "Lightway", 15 LED SMD, 120 lm, PIR, battery lights at £4.99 each inc 3 x AA batteries. Bought a couple. Trying out they are very bright, spots before the eyes bright, too bright for a "see where you're going" light during a power cut. They would also come on when the room lights where on, so a fairly high light level.
Opened one up (4 small screws) traced out circuit. All 15 LEDs are in parallel fed via a single 2R4 resistor. SPDT switch connects battery -ve either to this resistor (for ON) or the source of a FET, the drain goes to the resistor (for AUTO). The FETs gate is connected to pin 5 of an unmarked 8 pin chip. Ambient light level detection is a photodiode in series with a 820K resistor across a 3.3 V regulated supply. The juction between photodiode and 820K resistor is high with the photodiode illuminated and falls with light level and is connected to pin 6 of the chip. A PIR module is across the 3.3 V supply and its output goes to pin 7 of the chip. PIR module output goes high for about a second when it detects movement. Pins 4 and 8 of the chip are connected to -ve. Pin 1 +3.3 V. Pins 2 and 3 don't appear to be connected to anything either visually or trying continuity from them to elsewhere on the board.
Two simple mods bring the brightness down and make the "dark level" lower. Brightness is just replacing the 2R4 with something higher. I used 100R, might be a bit too big but still enough light to see by and with AA rather than AAA batteries they should last a very long time. "Dark level" I swapped the 820K for 1M, they no longer come on when the room lights are on.
Slight niggle is that the photodiode is partly shaded by the plastic tunnel for one of the LEDs so ambient light sensitivity is directional. Light sensitivity is also very quick to react. At lowish ambient light level waving an arm/hand nearby but not shadowing the photodiode the light doesn't switch on. Let the arm/hand shadow pass quickly over the photodiode and it does. I guess a small capacitor across the 1M resistor would slow the response down if this becomes an annoyance.
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