Wednesday, June 17, 2015

USB Current Monitor - Part 1

I, like a lot of other people, enjoy toying around with electronic components and in other ways making powered projects. While just setting up the circuit is fun in itself, I usually want to power it up once I'm done with the wiring. Unfortunately, I don't own any nice power supplies, so my computer's USB port ends up powering whatever I'm currently working on most of the time, through an Arduino or other microcontroller. One of the crucial aspects of any electronics project is how much current it draws, both for diagnostic purposes and power consumption predictions (think battery powered), but if I'm conveniently powering the project from a USB port, there isn't exactly a nice way to stick an ammeter in between the USB port and the connected device to measure the current draw.

So, thus brings rise to the USB Current Monitor project, a device that will allow easy and structured current draw measurements for other USB devices. I saw online that there were plenty of el-cheapo USB current measurement devices, but they all had physical displays on them, which seemed a little silly to me since they are plugged into a computer after all. My device will give accurate measurements, but more importantly they will all get logged on the PC they are attached to, all without interrupting the communications between the computer and the device being measured.

Also, since we are talking about hobby electronics, short-circuits are inevitable. Most computers have built-in protections against this, but if you're like me, you'd rather not risk your expensive laptop's USB port playing around with a few ICs. The USB Current Monitor will also feature a computer controlled current-overload protection circuit, so the device will automatically cut power to the USB port whenever the current draw exceeds a user-controlled threshold (such as would happen in a short-circuit).

This project is just beginning, but here are a few shots of the initial PCB layouts

Those sinkscreens that extend off the board will not be there in the final draft, I promise 

Cinematic isometric view

With the previous project I posted here being done with Eagle, let me just say that Altium Designer is an absolute DREAM to work in. The library structure is easy to work with, from creating schematic diagrams to automatically generating standard footprints with 3D bodies. Oh, and the whole 3D board view just might be the coolest thing ever.

I put in the order for all of the components to begin prototyping today and Digi-Key told me it already shipped! Good on ya, Digi-Key. Can't wait to get my hands on those components!

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