Created Thermal considerations (markdown)

Thermal-considerations.md

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+Even though LEDs consume far less energy than incandescent bulbs, these devices contain more complex circuitries and sometimes they still produce more heat than they can handle.
+The produced heat is proportional to the LED intensities, and if it builds up faster than how it dissipates from the chassis, then the temperature will rise.
+
+The circuitries usually (but **not necessarily**) contain some last-resort countermeasure that shuts down the device when it is critically overheated, but it shouldn't be relied upon.
+
+When testing the device for the first time, especially at higher light intensities, **monitor its temperature for some time**, like for at least half an hour, and if it rises rapidly, then please consider:
+
+- Reducing the overall brightness
+- Using only one of the light sources (i.e. either the color LEDs, or the high-power white ones)
+
+During this check please also consider that a bulb standing on your desk in a test socket has considerably better cooling than one in a closed armature right below your ceiling, so try to 'model' the operating conditions in which you plan to use the device.
+
+If you have found a solution that keeps the temperature stable, don't forget to **configure a limit in your home automation system** so you (or anyone else) won't accidentally set the device to overheating when it'll be already installed.
+
+Some of the devices' original firmwares do contain such software throttling, but as the thermal behaviour differs from one model to another, there is no generic way to apply the *right amount* of throttling that would be both required and enough for everyone, so "your mileage may vary".
+
+
+## Technical background
+
+Light bulb circuitries consist of 3 main stages:
+
+- A small power supply unit that converts the 230V or 110V mains to approx. 20V for the LEDs and 3.3V for the controller
+   This is a small switching-mode power supply, but usually of a parsimonius design, so it's usually barely adequate for the **average** power requirement, and sometimes not enough for the **maximum**.
+
+   The main problem is not the transformer, but the voltage regulators: they produce heat proportionally to the current that's drawn through them, and **they aren't connected to the heatsink**, so all their heat goes just into the air within the bulb.
+
+- The controller module, usually a SoC that contains the CPU, memory, flash and wifi.
+   It is a logic circuit, its heat production is negligible compared to the other stages.
+
+- The LED circuitry, meaning the LEDs themselves and their driver chips, usually on a separate board.
+   They produce a lot of heat, but they are always connected to the chassis via either thermal grease or thermally conductive glue, so they have a cooling.
+
+So the problems are:
+- Voltage regulators produce heat proportional to light intensity
+- Their thermal coupling to the chassis is terrible: via a huge air gap
+- The chassis is not an effective heatsink (for aesthetic reasons it can't be)
+- The overall system is designed for the average conditions and not for the maximum.
+
+
+## Measured Values
+
+These were measured on a SYF05 (Fcmila/Sunyesmart) bulb with full intensity on all LEDs:
+
+Chassis Temperature
+
+- At start: 23.4°C
+- After 10 minutes: 39.2°C (warm)
+- After 20 minutes: 47.7°C (hot)
+- After 30 minutes: 52.6°C (barely touchable)
+- After 40 minutes: 54.8°C
+
+At this point the thermal protection has shut the device down, and the local temperatures were:
+- Chassis: 55°C
+- RGB LED driver chip: 73°C
+- White LED driver chip: 76°C
+- Controller module: 76°C
+- Transformer: 85°C
+- Area around the voltage regulator: 91°C