Useless Power Indicator

Energy can travel around the world but still can't go through a simple LED

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The humble power indicator LED. It gives you confidence that your device is actually receiving power so the reason it's not working is definitely a mistake you've made. It's the most basic element on a PCB only requiring an LED and a current limiting resistor that you just expect to work. Simple and straightforward and really useful.

A complicated way to design an indicator is to store and get data from the internet of whether the the device is receiving power and whether the LED should be on or not. This is potentially even helpful in the case of IoT to know over the internet that your device is actually operating.

But since this is a useless LED why not just get the RSS feed to decide if the LED turns on. Maybe the indicator might actually turn on for a while unless someone decides to post an article which is guaranteed to make debugging that little bit harder.

  1. Insert working SIM card
  2. Plug in power at the input
  3. Plug in your project at the output.
  4. Turn on? the switch
  5. ???
  6. LED lights up to show your project is powered?

Features a large novelty LED that makes it 100% both more AND less clear if your project is receiving power.

x-csrc - 6.59 kB - 08/06/2019 at 14:29


Useless Power Indicator.sch

Kicad Schematic

x-kicad-schematic - 25.74 kB - 08/06/2019 at 15:05


x-kicad-pcb - 129.70 kB - 08/06/2019 at 14:29


  • 1 × ATtiny87 Microprocessors, Microcontrollers, DSPs / Microcontrollers (MCUs)
  • 1 × MCP1700-330 Power Management ICs / Linear Voltage Regulators and LDOs
  • 1 × MIC29302A Power Management ICs / Linear Voltage Regulators and LDOs
  • 1 × SIM5320

  • Project complete

    Autofix08/06/2019 at 14:41 0 comments

    Added large novelty LED and adjusted layout to fit.

    Changed some 3d models to the best of my ability.

    Completed C code that should connect the SIM5320 to a mobile network, connect to and retrieve the RSS feed, and then based on that decide if the LED should turn on or not.

  • PCB layout in progress

    Autofix07/26/2019 at 16:41 0 comments

    I've laid all all the components, but exact positioning/board size is still up for change,

    I also tried out Kicad StepUp plugin with Freecad to make some missing 3D models, but I still need to work out blender for adding the correct surface textures.

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Ken Yap wrote 07/26/2019 at 23:00 point

>Electrons can travel around the world

Back in high school one of the questions at the back of a chapter in a physics book asked us to use the electron density of metal and the amount of charge in a battery to work out if an electron could make it from the negative pole to the positive pole over a wire within the lifetime of the battery. Answer was it could not. In reality electrons only travel a short distance. What is traveling is really the charge "pressure" (for my lack of the correct technical term). But we can continue to imagine they travel long distances as electrons have no individual identity. The electron that came off this end of the wire is as good as the one that went in the other end.

Fascinating fact for today. 😉

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Autofix wrote 08/06/2019 at 14:33 point

You're definitely correct. I felt it was more entertaining to talk about something physically traveling around the world, but I've changed to energy which more technically correct.

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