Emergency or Inverter Bulb Working Principle

Some of you may have seen these bulbs in your home. At first glance, they seem like your regular LED bulbs, with a string of LEDs powered by AC input. But here’s the twist: they hide a rechargeable battery inside, often an 18650 lithium cell. When the power goes out, this battery springs into action, illuminating a subset of LEDs.

You can get a pretty good idea of what’s packed inside these LED bulbs. It typically includes a standard bridge rectifier and an LED driver for the regular lighting component. There will be a battery charge controller, ensuring the battery gets juiced up during operation. When the power goes out, the battery takes the wheel, supplying power to the LEDs. It’s a straightforward setup, nothing too complex

But here in lies the interesting part, how will the LED know to turn ON when there is no power? Because it can also be that its switch to it is turned OFF. How does it differentiate? It uses a clever mechanism, it can turn ON only when the input AC terminals Live and neutral provide a momentarily closed path. This cannot happen in the normal case and can occur only if another load in the same circuit is also turned ON. It could be any device. This will provide a path for the battery to turn ON power to LED till the actual AC power kicks in.

Consequently, you can perform a seemingly magical feat by merely touching the LEDs with your hands (a reasonable resistance between the AC input pins triggers the battery to power the circuit). It’s a neat party trick that can impress your guests when you effortlessly illuminate an ordinary-looking LED bulb with no external power source, using just your hands! ?

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Rant: The USB Type C Cable Chaos

USB Type C Breakout Board

Recently, I misplaced my OnePlus phone’s charging cable and resorted to a Type A to Type C USB3 cable with their original charger. Voila, OnePlus’s superfast charging didn’t kick in with the alternate cable, even though it was of better quality than their official one. This is not a new dilemma; I was curious about how they detect the cable change. Looking at the Type A end of the cable, it appeared similar to a regular USB2.0 Type A connector with the standard four lines: VBus, D+, D-, GND. Interestingly, there was an exposed middle GND-Drain line, which seemed odd. My hunch was that they might be employing some non-standard 1-wire communication over that line.

To delve deeper, I attempted to use a USB TypeC Breakout and probed each pin on the Type C end, but the GND-Drain pin wasn’t connected anywhere. This strongly hinted at the use of an eMarker chip in the cable head. These minuscule chips play a pivotal role in communication between devices and chargers, and that’s where the conundrum arises.

USB Type C cables were intended to establish uniformity and standards, but the industry has managed to turn it into a colossal mess. The market is flooded with seemingly identical Type C cables that differ drastically in performance. And that’s just the physical design part – add to it the proprietary charging protocols introduced by each company. From Apple to Samsung, Qualcomm to Xiaomi, and OnePlus/Oppo, every brand is pushing its unique charging approach, accompanied by flashy names like QuickCharge, Dash/Warp Charge, SuperCharge, and PD fast charging. Just to figure out the Voltage and Current needed.

What’s preventing companies from adhering to a universal standard? The lucrative $50+ billion cable and accessories market. If you purchase a device, you better buy its specific cables or risk a drop in performance due to vendor lock-ins. This issue becomes even more vexing today as companies often exclude chargers and cables when you buy a phone.

This mess won’t be sorted out anytime soon, with USB4 introducing more confusion. Wired cables will be weird in the years to come.

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