Didier Stevens

The Dutch government is telling people to prepare to be self-sufficient for at least 72 hours in case of a major emergency when many services (electricity, water, internet) could be unavailable. This campaign is called “Denk Vooruit” (Think Ahead). An emergency booklet has been mailed to all inhabitants. The Belgian authorities are voicing similar concerns, but no emergency booklet has been mailed.

The booklet advises people to have a radio in their emergency kit, specifically one that works without mains power, like a battery-powered or hand-crank radio.

I have a battery-powered FM radio, and I wanted to know if I could power it with a USB powerbank and a USB trigger board (I have several high-capacity powerbanks).

It works: the radio has a 12V barrel jack connector, and I can power it with this USB trigger board/cable, without soldering connectors:

I’ll probably still solder a cable with a fixed 12V USB trigger board, because this setup is prone to accidentally pushing the button of the USB trigger board, and delivering 15V or 20V to the radio (a voltage that is too high, and might destroy the radio).

Although this setup is portable, it’s not very handy to carry around when you go away from home. So I looked around on Aliexpress for a small & cheap FM radio and selected a Junus J-555. It can be powered by two alkaline AAA batteries or by its built-in Li-Po battery. That Li-Po battery can be charged via a USB-C connector, and the radio also works while charging. But what is most important: it has a good reception of FM and AM stations when operating inside my home.

In blog post “Quickpost: USB Electric Razor” I mention USB trigger boards.

A USB trigger board is a small electronic device that receives power via a USB-C connector, and delivers power with a voltage that it negotiates with the USB power source.

This one for example is set to deliver 12V:

Left you have the USB-C connector, right you have positive and ground soldering pads with 12V between them.

Here is one that can be configured with DIP-switches (5V, 9V, 12V, …):

The USB-C connector is on the left, and you have screw connectors on the right for the output.

Here is one with cables, and a display and switch that lets you cycle between 5V, 9V, 12V, 15V and 20V.

The USB-C cable is on the right, and a cable with a barrel jack connector is on the left, delivering 12V in this example.

And here is one that is even more configurable:

A USB-C connector on the left, and a USB-A connector on the right with a USB-A cable with barrel jack connector. It’s configured for 5V.

This one can not only negotiate fixed voltages (5V, 9V, 12V, …), but also arbitrary voltages via Programmable Power Supply, provided your USB power source supports PPS. For example, one can request 5.5V, and also limit the current, to say 0.1A.

And finally, I also have this Fnirsi DPS-150, a portable power supply that can also be powered via a USB-C connector:

It’s not a USB trigger board, but more like a lab power supply. It is limited by the power it receives from the USB power supply. For example, on the picture above, you can see that it negotiated 20V (20.07V) with the USB power source, it is set to deliver 20V (Vset), and delivers 19.83V (unloaded). The dial button can be used to set a voltage between 0V and 19.83 (in this example). The maximum current can also be set (Iset).

These boards allow me to power devices with various power requirements, and be mobile.