Tag Archives: USB

Powering a Ham Radio with USB Power Delivery

A while back, I built a cable to power 12V devices (in my case a Kenwood TH-D74 HT) using the QuickCharge standard available in some USB power adapters. This allowed me to use a USB charger to charge my HT rather than bringing a dedicated wall wart which helped save some space when I traveled. While my homemade cable was electrically simple and worked as expected, it was a bit clunky. Also, QuickCharge is largely being replaced by USB Power Delivery (USB-PD), and since my laptop chargers using USB-PD, I found that I could consolidate my charging needs further by getting an adapter that works with USB-PD. 

Of course, I’m not the first person to try to adapt USB-PD for other purposes, so I was able to find a few products that partially solved this problem. I quickly came across a line of small adapter boards that negotiate the USB-PD protocol and provide an adjustable or preset voltage based on the standard. These are available on Amazon (affiliate links on this page) but can also be found even cheaper on eBay if you’re willing to wait for shipping from China.

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USB Quick Charge 2.0 Adapter for 12V Non-Quick Charge-Enabled Devices

As I got interested in roving more for satellite operations, I was looking for ways to slim down the equipment I needed to carry, particularly on trips that require a flight. While packing one night, I noticed I had a Tronsmart WC2F USB power adapter that supports the Qualcomm Quick Charge 2.0 protocol. This is one of several protocols that let devices use higher voltages and currents over a standard USB A connector. There are a few versions, but in short, this protocol allows for the USB power adapter to supply 12V at 1.5A, among other less interesting voltages (to me anyway). This seemed like a perfect way to charge my 12V devices – my Kenwood TH-D74, Ailunce HD-1, and Yaesu FT-817ND – without having to bring along an additional wall wart.

After digging a bit, I found an article on Hackaday where someone made a custom power adapter using Digispark, a modified regulator, and some simple handshaking code. Going down into the comments, Sam Mallicoat mentions the handshake can simply be done with a couple resistors and a momentary switch. Even better, Horst Leykam replied that a regular old latching SPST could work instead of a momentary switch. Aha! Since I was trying to keep this compact, this seemed like a great option compared to adding a microcontroller to the system. My plan was to made a cable adapter with an in-line switch that contained the resistors. A USB A male connector on one end and 2.1mm barrel connector on the other would give me good compatibility with my devices.

12V Enable Circuit for USB QuickCharge 2.0

For the switch, I ended up buying a simple Leviton in-line lamp cord switch which is large enough to hold the resistors inside and can be found online or a hardware store. I unfortunately didn’t take photos at the time, and I admit it wasn’t pretty inside; I had to use some hot glue to keep wires where I wanted them and rip out the regular lamp cord contacts. But still, it was not too difficult of a project.  As this uses a SPST switch, the operation is as follows:

 

    1. Plug USB cable of adapter into Tronsmart
    2. Cycle the adapter switch to off (if it’s not off already)
    3. Switch adapter on
    4. Voila! After a moment, 12V will be coming out on the barrel connector

Note that this switch does not control power entirely; when the switch is in the off position and before cycling it, it will still be outputting 5V. This is likely not an issue for a 12V device, but of course, proceed at your own risk!

While I know my adapter could be prettier, I’ve been happy with it so far. I have 2.1mm y-splitter cable which allows me to charge two devices at a time, usually my D74 (with a small connector adapter) and HD-1 or D74 and 817ND. While it could actually run one of those devices at a time based on its current capability, the inexpensive switching regulator in the Tronsmart is expectedly noisy, so this really should only be used as a charger. Since the Tronsmart is a dual USB port charger, I can bring this adapter to charge my radios and iPhone or iPad all from the same outlet at the same time.