A small battery-driven portable "bench" power supply

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Blue Smoke Electronics is proud to present a new type of power supply. Ember is a small sized, battery-driven power supply with the features you normally would expect in a traditional bench power supply.

Why do I need a bench power supply?

Engineers and scientists use bench power supplies when working with low-voltage DC electricityTwo features make a bench power supply very useful: adjustable voltage and current limits.

As a voltage source

Adjustable output voltage means a power supply can be used as a voltage source, which is part of almost all electronic circuits. It also means that you can use Ember instead of different kinds of batteries.

As a current source

The power supply is a current source when the current limit is applied. While less common than voltage sources, they are used in many electronic circuits. For instance, you need a current source when lighting up a LED.


Setting the current limit just above what you expect is common practice when testing new circuits. That way, the chance of something being damaged is reduced if something is wrong.

Why portable?

As the name suggests, traditional bench power supplies are designed to be stationary on your workbench. This is fine for most projects, but for some projects, you must take out an extension cord and a trolly to bring your power supply into the field. Blue Smoke Electronics has designed a portable version to make this process easier. You don't need an extension cord; the power supply fits in your pocket.

Outdoor projects

Need to repair something in your car? Are you not allowed to fly drones indoors? Homemade firework display? Some projects are not a good idea inside your home, and you can power your projects up outside with Ember.

Work from home?

Sometimes we have to work on weekends. Wouldn't using your prototype on your living room table be better than going to the lab to test the new firmware patch?

Around the house

Let's say you are setting up a servo that automatically opens a window. Then you can hide an Ember behind a curtain until you can get your permanent wiring done.

On the train

Do you have a long commute? Then Ember is perfect for your portable lab suitcase.

Store it in a drawer

Do you have your own space dedicated to electronics at home? Do your kids? If this is more of a hobby to you, choose a power supply that is easy to stove away when not in use.

Benefits of a battery

Not needing to be connected whit a cable all the time is one of many benefits of having a battery internally in Ember.

Energy buffer

The battery acts as a buffer. It stores energy over time and can deliver high-power bursts when necessary. A weak power source like a USB port can then be used to drive devices that sometimes have a high energy need. Servo-motors are great examples of components that need a lot of energy when moving and, otherwise, nothing.  This allows the battery to charge back up when the motor isn't moving.

True isolation from the grid

For some RF-sensitive measurements, you want to be sure that no noise is coupled from the power grid into your electronics. Disconnecting completely is an excellent way to ensure no signal is coming from the grid. Physically being disconnected also eliminates the possibility of ground loops.

No risk of electrocution

The voltage levels in the device are, at most a few volts. This makes getting a dangerous electric shock impossible, even if you do something foolish like taking it with you for a swimDon't use a power supply connected to 230V when testing RC boats in the bathtub.


A complete list of specifications can be found here. The most important specs are:

  • Voltage from 0-15V
  • Current from 0-1A
  • 7.0 Wh battery life
  • Charging via USB-c
  • Controllable via USB-serial interface
  • Dimensions: 85x75x40mm
  • Weight: 150g


Mechanical drawing of binding post, used to turn your own binding posts

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Standard Tesselated Geometry - 153.01 kB - 06/28/2023 at 12:54


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  • Battery Under voltage Corner cases

    Simen Sollihøgda07/07/2023 at 07:06 0 comments

    Ember's battery, a li-ion batteries doesn't like to be completely drained. At least not below 2.5V; so the datasheet says. The software in the mcu, a RP2040, stops the battery from being drained by monitoring an ADC and disconnecting when the battery voltage gets below 2.85V. I do trust the mcu, but  I also really don't want the battery to be explosively mad. That's why I decided to run a few tests to see what happens when the undervoltage shutoff code is disabled. 

    One Ember laying naked(no enclosure) on my desk with two other Embers trying to keep it alive. One connected to the battery terminal gradually decreasing the voltage, the other connected to the USB port, simulating a charger. It sure is nice to have a loot of power supplies around when working on a power supply.   

    At around 2.7V bad things started to happen. The display suddenly darkened and the power draw from the battery(simulated) tripled. I also noticed, the hard way, that the 4.2V booster was hot. Not hot enough to instantly cause blisters, but hot. The 4.2V booster powers the backlight for the display and that why when it stopped working, the display darkened. The MCU is also powered by the 4.2V booster, and this is how I found the second bug of the day. 

    When the booster stops working, and the voltage to the mcu drops everything freezes. The display stops updating and input is not registered, not even from the power off button. This is bad, the device should power off when the battery is low. RP2040 has a feature, it stops the code execution and gives an  error message. This is great for debugging when you want to know what just happened, not so great when you are battery powered and the mcu just sitting there waiting for someone to read the error message, slowly is destroying the battery. 

    "Woff! Woff!" The watch dog timer does still work when the processor stops execution. When enabled the watchdog can be used to reset the mcu and power off the device. Enabling the watchdog timer took only a few lines of code and I think it may save me from other unexpected bugs as well. 

    As for the 4.2V booster issue, I was using a inductor with a too small current rating and I think it go saturated. Replacing the inductor with one a higher current rating did at least fix the problem. 

  • Constant current indicator implemented

    Simen Sollihøgda06/30/2023 at 12:22 0 comments

    It can be it can be easy to overlook that the power supply is in current limiting. I have therefore added a small indicator in the display that shows up whenever the power supply is in current limiting mode. The indicator is the two letters "cc" that shows up on the side of the current limit setting. 

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  • 1
    1. Order pcb
    2. Order non jlcpcb parts
    3.  Turn the binding posts 
    4. Solder on parts
    5. 3dPrint enclusure
    6. uploading software
    7. Assembely 
    1. 2
      Order pcb from JLCPCB

      Download gerber, cpl and bom files to your computer

      go to and select PCB Assembly

      upload gerber file

      The Dimentions should automaticly update to 80 x 65 and number of layers to 4. leave all other choices as default. 

      Enable PCB assembely and select standard and both sides. 

      When asked about PCB Size Requirment click OK 

      Then you will be asked to upload bom and clp files, do so

      You will then get a list of all parts in the project that are going to be assembled. 

      There may be some parts that is out of stock. What I have done in that case is that I have ordered the missing parts from and soldered them on manually. 

      The 618 part is the display, and I always solder them manually. That's also the case with the 6.35mm_mounting_hole witch is where the binding posts will be attached.  

      To reduce cost of the assembly I also leave the 1043 battery connector unassembled at do that by hand later. 

      Next is component placements. It could be fine to leave this as is, but take a look to see that it looks like all the parts are in the right place. 

      The components that is missing is the components that was out of stock. 

      At last you get a summary of the cost of the assembly. Click save to cart and you should be able to pay for the board. 

      Using the PCB assembly can be quit expensive when you only need a single board. If you have some skill with a soldering iron and some spare time you could order the pcb from JLCPCB and the parts from Digikey, and then assemble the board yourself. 

    2. 3
      Order non jlcpcb parts

      You will need a few more parts to complet you assembly. 

      • A 18650 li-ion battery rated for 20A+. I am using  Sony 18650 VTC5.
      • 4x m2 threaded brass inserts
      • 4x m2 22mm screw with hex head 
      • a 2.4" display from adafruit, partno 618
      • A 12mm brass rod
      • black and red paint

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