43oh

# ToF

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## Reputation Activity

1. ToF reacted to roadrunner84 in Hi from Weimar, Germany
Energy efficiency will be low indeed, but if I need to install one SMPS instead of 6 throughout a room, that will more than make up for the inefficiency of the optical energy transport

I'm Dutch, which you may know is very similar to German. Also, we were required to attend German (and French) classes in secondary school.
2. ToF reacted to bluehash in Hi from Weimar, Germany
Good intro! Welcome to 43oh. Energy harvesting is a good topic. It's catching up slowly.
3. ToF reacted to roadrunner84 in Hi from Weimar, Germany
Guten tag, wilkommen auf diesem Forum.

I am able to get meself understood in German, but I don't write it that good

Energy harvesting is a cool subject, I'm currently brainstorming about powering and connecting small nodes via fiber; have the node powered by the energy emitted in the light pulses also used for communication.
4.
USB chargers convert 12V to 5V and can supply at least 500mA. They must be using switching regulators, otherwise the heat would be excessive. They have the necessary protection circuits. And they cost about \$5...

I would really recommend getting one and then either try to change the output to 3.3V like cde suggested, or just use your LM317 to go the last step to 3.3V. I would suggest the latter, because it gives you a nice and smooth supply, something a cheap china-made charger might not provide.
5.
You're regulating 12 volts down to 3 volts. Thats 9 volts difference. Let's assume you draw 20mA (I don't know exactly how much power a Launchpad draws, or all the logic you need to power from 3 volts). This means you need to convert 180mW to heat (9V*0.02A). The LM2937 in TO220 case has, according to the datasheet, a thermal resistance of 53K/W (page 8), meaning its temperature will rise about 10 degrees (celsius) above ambient. If you draw 40mA, it will rise 20 degrees. 100mA would mean nearly 50 degrees above ambient, enougt to burn your fingers. (The TO-263 and SOT223 cases have an even higher thermal resistance, meaning the will get even hotter with the same load)
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