Powering my Raspberry Pi with the BeagleJuice, 2nd Gen Battery

My Raspberry Pi finally showed up today! Naturally, an unboxing event was in order…

I haven’t gotten around to setting up my SD card yet, but I just wanted to see if it would power on with the BeagleJuice sitting on my desk. In theory, it should work, since the BeagleJuice outputs 5V from each of the 2-pin molex connectors.

I took the micro USB cable that I spliced last week and plugged it into the Raspberry Pi…

…then I connected the other end to the BeagleJuice.

And voila! The Raspberry Pi powers on, as indicated by the red power LED next to the audio jack. Just for kicks, I plugged in the BeagleBone to the BeagleJuice as well (with a 5V barrel jack) to make sure they both run simultaneously, and they do :-)

3 Useful Things to Know about the BeagleJuice, 2nd Gen

I got a few very good questions about the BeagleJuice, 2nd Gen from earlier this week, so I thought I’d answer them in post form.

What are the specs on the I2C pins on the BeagleJuice?

The I2C pins (GND, Vext, SDA, and SCL) are exposed for custom headers or wiring. After bugging Chris several times, he decided to just draw me a schematic instead. The range of operation is 1.8V to 3.3V. Currently, there are drivers coded for Android/Linux and OMAP, but it could be hacked to anything that talks I2C.

What else can I power with the BeagleJuice?

The BeagleJuice comes standard with the 2.1mm barrel plug, which works just fine with the 5V barrel jacks on the Arduino, BeagleBoard C5 and xM, PandaBoard, as well as the BeagleBone.

That said, it is in fact just a 2-pin molex connector at the end, so Matt spliced up his own USB micro cable, put some heat-shrink on the tip, and voila! The BeagleJuice now charges anything that takes 5V – my phone, or even the Raspberry Pi (when mine finally arrives!).

What’s with the strips of LEDs?

Aside from the fact that LEDs are always fun, they actually serve a purpose.

The ones on the left are battery charge status indicators, which were inspired by Chris’ Macbook Pro battery meter. (Sorry the picture is a little blurry – I tried to catch it as the lights were moving up!)

There are a couple more “easter eggs” on the BeagleJuice, 2nd Gen – mostly holdovers from things Chris, Mike and I were working on here at the lab. Post your thoughts or guesses to the comments, or just send me a note – justin dot huynh at liquidware dot com

Introducing the BeagleJuice, 2nd Generation: Laptop-Grade Power Management for the BeagleBoard

Last week, I took a trip through some of the battery boards and power management systems we created for the Arduino, BeagleBoard and Amber. The development of the 2nd generation BeagleJuice was inspired mostly by requests for a “standalone Amber backpack”.

Sort of…I took a little artistic license with the picture above! The Liquidware Amber power supply and BeagleJuice, 2nd Gen were both built with advanced power management principles in mind.

(Edit: I got a few questions about this - the BeagleJuice, 2nd Gen comes with the standard 5V barrel jack cable to charge any 5V device that fits the jack, like the BeagleBone or PandaBoard. For the adventurous, it's not a huge stretch to wire your own cable to the 2-pin Molex connector...)

The 2nd Generation BeagleJuice is a modern, laptop-grade power supply that implements smart charging technology to manage multiple cells in series to deliver higher charge capacity, as well as high-power output. It’s optimized for 2-cell, 3-cell, and 6-cell configurations to deliver 2800, 4200, or 8400 mAh of capacity.

Onboard LEDs provide multiple status readouts as well as charge information. Advanced features can be accessed over I2C pins directly, or via a Zero Insertion Force (ZIF) ribbon connector. Here at the lab, I’ve used the 2nd Gen BeagleJuice as a primary power supply for several BeagleBoard units concurrently – which centralizes the power management system for remote installation clusters. The high-capacity BeagleJuice provides quad 5V outputs via discrete 2-pin Molex connectors.

I’ll cover some details on charging cycles in the next blog, but in addition to smart charging and power input management, the heavy-duty power supplies that the BeagleJuice is modeled after also focus on being fault tolerant and providing an added measure of battery preservation. This “safety” logic protects the battery from:

• over current charge/discharge
• over temperature charge/discharge
• over voltage charge/discharge
• cell charge/discharge imbalances

While no system is perfect, taking these issues into consideration is a big step closer to advanced power management and portable power supplies, useful for hobbyist and embedded prototyping projects with the BeagleBoard alike. Since the BeagleJuice, 2nd Gen comes with 2 5V barrel jacks connectors, it can actually power the PandaBoard and Arduino, as well as my phone with a custom-spliced USB connector. Here’s a quick shot of the new BeagleJuice in action:
This is Part 2 of 3 on portable power management for prototyping embedded systems. The next post will walk through some of the charging algorithms and explain some of the complexity around charge management ICs - justin dot huynh at liquidware dot com