Pure Siesta Mi UPS (Uninterruptible Power Supply)

Introduction: Pure Siesta Mi UPS (Uninterruptible Power Supply)

As these alarm clocks use Mini USB for their power supply, you can construct a very simple UPS using parts available on the likes of eBay. This is possible on both the Series 1 (pure in top left corner & Siesta Mi in top right corner of front) & Series 2 (pure written below screen) version.

Parts you will need

  1. A battery pack (e.g. A battery pack which charges from USB and gives you a USB port for powering/charging a device). It also needs to be capable of outputting around an Amp (at least 800mAh) of power to be able to supply the alarm clock at full consumption.
  2. A USB A male to USB Mini A male cable. These are very common (on most hard drives, cameras, card readers & etc) and are likely available in your local Pound shop. Note: Some very cheap cables are of a poor quality and can't carry necessary current.
  3. If your battery has a Micro USB socket for charging (mine does), you will need a Mini A USB female to Micro A USB male adapter. These can be bought on eBay easily. NB: Photo does not feature this, as mine hadn't arrived yet. I used another generic Micro USB phone charger temporarily.


  1. Disconnected the clock's power connector from the under-side of Pure Siesta Mi (the alarm clock will turn off).
  2. Connect the Mini USB connector of your USB A male to USB Mini A male to the power connector of the alarm clock. You may turn the alarm clock back the right way up when this is done.
  3. Connect the A connector of the above cable to the battery pack. If there is charge in the battery, the alarm will likely turn on now.
  4. Now connect the Mini A USB female to Micro A USB male adapter to the alarm clock's power supply.
  5. Lastly, you can connect the adapter above (with the power supply connected) to the power-in socket on the Battery Pack.
  6. Make sure it's plugged in and turned on at the wall. Otherwise the battery will run out!
  7. Fin.


There are a few possible issues which you may encounter.

  1. When the alarm clock is in standby mode, the power goes off completely. This may occur if the power pack has circuitry which detects whether something is connected to it, but doesn't detect the low load of the alarm clock in standby mode. In this instance, you will have to keep trying different battery packs until it works for you. I've had success with a Dynamode Power Bank (around £5), but I think they have discontinued making them.
  2. The battery pack runs out while listening to radio. In this case you may want to invest in a more "beefy" power supply that can power the alarm and charge the battery at the same time. I suggest a Mains Adapter of at least 5V 1Amp (or 1000mAh), this should give you enough headroom for both.
  3. The batter pack / mains supply gets hot. It will, these devices are not 100% efficient and will give off the rest of the power as heat. You can upgrade the battery / power supply to one with a higher power rating to try and fix this.
  4. Lower Signal Strength on DAB. I encountered this, but using a shorter cable between the battery and the alarm clock improved it, though I don't know why!



While the alarm remembers all of it's settings at a power loss (including alarms & preset stations) and reacquires the time from the DAB/FM signal. I felt that as it was such a simple hack, it was certainly worth doing. Plus, being self employed, I could loose a lot of business for being late, even if only being late once!

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    2 Discussions


    5 years ago on Introduction

    Generally the battery packs either discharge or charge, but not both. How did you select a battery pack that acts like a UPS?


    5 years ago on Introduction

    This is an awesome project. Smart gadget hack, decent text layout, helpful instructions... but it could really use some process photos. I send projects like this to the homepage all the time, but this one has too few process photos.