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Archive for the ‘wall wart’ Category

USB chargers are everywhere and it is the responsibility of every hacker to use this commonly available device to its peak potential. [Septillion] and [Hugatry] have come up with a hack to manipulate a USB charger into becoming a variable voltage source. Their project QC2Control works with chargers that employ Quick Charge 2.0 technology which includes wall warts as well as power banks.

Qualcomm’s Quick Charge is designed to deliver up to 24 watts over a micro USB connector so as to reduce the charging time of compatible devices. It requires both the charger as well as the end device to have compatible power management chips so that they may negotiate voltage limiting cycles.

In their project, [Septillion] and [Hugatry] use a 3.3 V Arduino Pro Mini to talk to the charger in question through a small circuit consisting of a few resistors and diodes. The QC2.0 device outputs voltages of 5 V, 9 V and 12 V when it sees predefined voltage levels transmitted over the D+ and D- lines, set by Arduino and voltage dividers. The code provides function calls to simplify the control of the power supply. The video below shows the hack in action.

Quick Charge has been around for a while and you can dig into the details of the inner workings as well as the design of a compatible power supply from reference designs for the TPS61088 (PDF). The patent (PDF) for the Quick Charge technology has a lot more detail for the curious.

Similar techniques have been used in the past and will prove useful for someone looking for a configurable power supply on the move. This is one for the MacGyver fans.

Filed under: Arduino Hacks, hardware

Don’t buy a cheap plugpack…

ebay, education, learning electronics, plugpack, repair, voltage converter, wall wart Commenti disabilitati su Don’t buy a cheap plugpack… 

Hello readers

Now and again in the quest to save money, or to buy something that you need when you are short on cash, you inevitably end up trawling through eBay for what you need. Last month I needed some 20V DC 1 amp plugpacks to test my bbboost prototypes with, so naturally after scoping out retail prices eBay found itself on my web browser. Considering a local alternative costs $38, it was worth a shot. As these were for ‘internal use only’, that is for myself and nobody else, it is ok for me to buy the cheaper option. Well it used to be.

These suckers were found for $5.20 delivered from Taiwan…

No C-Tick or electrical authority approvals on this plug pack…

The first problem was the plug – these were advertised as having Australian plugs, however it was the US-style with adaptor. Naturally the adaptor didn’t fit, and I had to disassemble and rearrange the contacts inside for it to accept the flat pins. Second problem was the heat – this little monkey would run hot, even without a load. I asked it for around half an ampere and it really cooked. Ouch!

In the words of Dave Jones – “it’s a piece of sh*t!”

So what else was there to do? Wait for it to cool down, and pull it apart!

Wow – what a mess. Even through the electrolytic capacitors looked normal, there was a layer of brown, rusty goop all over the back of the 2n60C MOSFET. Where did that come from? The mind boggles. Everything else looked normal, the PCB was soldered nicely and the capacitors weren’t bulging or leaking. There were holes for a 1k0 resistor and an LED, but they were unused. What else to do? I cut the DC lead from the housing and soldered a 9v PP3 battery snap on the end – perfect for using an Arduino away from the desk for prototype testing…

So the exercise was a not a total waste… the DC plug is worth $2 locally, and the wire was probably worth about fifty cents. The plastic housing might be useful later on.

From now on I think it will pay to fork out for an approved, locally-sourced adaptor. No more eBay! So remember, quality is remembered long after price is forgotten.

High resolution photos are available on flickr.

As always, thank you for reading and I look forward to your comments and so on. Please subscribe using one of the methods at the top-right of this web page to receive updates on new posts!

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