![]() At the far right is a buffer which then drives the previously mentioned large serpentine transistor to the LED pad. Near the left is misc logic, then two shift rigisters, then an EXOR gate, then five additional shift register cells. Region three has several cells wired as shift registers. The second horizontal region has several EXOR gates (center) which combine outputs from the divides chain, along with various outputs from region three below. Additionally various taps from the divider chain are used in the second horizontal region. The upper band (just below the GND pad and extending across to the LED pad) is a 9-stage divider chain along with miscellaneous logic at right. The middle of the chip has three horizontal bands. The drive transistor is center bottom with four T-flip-flop divider stages repeated to the lower left of the chip. With the serpentine resistor connected to the upper left of this pad, this, forms the on board RC oscillator. In the lower region, to the left of the VCC pad, is a similar pad which forms a capacitor. To the left of the LED output pad is the large serpentine LED driver transistor.īetween the GND pad and serpentine transistor is Power on Reset with the metal plate the capacitor and a long trace loop to form a resistor for an RC time constant. Not the best chip photo, but consider the circumstances. Might keep em out of your hair for a little while! But if you made this looking nice it’d be a cute thing to have for xmas and probably impress a few little kids. ![]() I suppose if you wanted it super safe you could make the match itself out of an LED on a stick. Perhaps a half-litre / 1-pint bottle would be good. ![]() The candle-carrier in the one I saw was a cut-up plastic milk bottle, with the LDR mounted on the upper part of the handle, cut off there while the guts go in the bottom bit. If you wanted to make this using LEDs instead of a bulb, you’d either need to include a constant non-flickering LED, or a capacitor to store a bit of voltage to keep it switched on for the milliseconds while the LED flickers. The bulb starts out dark, but lighting a match and bringing it to the LDR “lights” the candle! To extinguish it, you blow it out, subtly cupping it so your hand breaks the beam going to the LDR. The LDR faced the bulb directly, mounted in a sort-of pewter candle carrier thing, the thing Victorians took to bed. While the lamp shone, the LDR kept conducting, which kept the lamp shining. ![]() An LDR controlled the bulb through a simple transistor switch. One I heard about ages ago (which actually used a torch bulb, back when they existed. Posted in LED Hacks Tagged AVR, candle ficker, linear shift feedback register, pseudorandom Post navigation took the lessons learned and wrote an implementation of the algorithm for AVR. It turns out a blinking LED can be quite complex, and this takes a deep look into it by analyzing the signal. determined that a linear feedback shift register was most likely used to generate a pseudeorandom bitstream, and some shaping was applied to make the LED look more like a real candle. This control signal looked like pulse width modulation, with some randomness to the duty cycle. By connecting this resistor to a logic analyzer, the control signal could be observed. To analyze the circuit, which is potted into the LED itself, a shunt sense resistor was connected to the LED. took a deep look into reverse engineering one of these LEDs. They contain both a yellow LED and a control chip that modulates the light to create a candle effect. Candle flicker LEDs are a one part replacement for a real candle.
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