Ode To The TL431, And A LiFePO4 Battery Charger

January 8, 2016 by Elliot Williams 85 Comments

Nerd Ralph loves cheap and dirty hacks, and for that we applaud him. His latest endeavor is a LiFePO4 battery charger that he made out of parts he had on hand for under $0.50 US. (Although we think he really made it for the fun of making it.)

The circuit is centered around a TL431 programmable shunt regulator, which is an awesome and underrated chip in its own right. If you don’t know the TL431 (aka LM431), you owe it to yourself to fetch the datasheet and pick up a couple with your next electronics part order. In fact, it’s such a great chip, we can’t resist telling you about it for a minute.

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Better Batteries For Electronic Gadgets

September 6, 2015 by Brian Benchoff 46 Comments

We’re not using 9 Volt batteries to power our projects anymore; the world of hobby electronics has moved on to cheap LiPo batteries for most of our mobile power storage. LiPos aren’t the best solution, evidenced by hundreds of YouTube videos of exploding batteries, and more than a few puffy cells in our junk drawer. The solution? LiFePO4, or lithium iron phosphate cells. They’re a safer chemistry, they have low self discharge, and have more recharge than other chemistry of lithium cells.

LiFePO4 cells aren’t easy to deal with if you’re working with breadboard electronics, though. Most of that is because there aren’t many breakout boards for these cells. [Patrick] is working on changing that with his LiFePO4werd USB charger.

The concept is simple: use an off-the-shelf part for LiFePO4 batteries – in this case an MCP73123 – and make a board that charges the batteries with a USB port. It’s exactly the same idea as the many USB LiPo chargers out there, only this one uses a better battery chemistry.

[Patrick] is using a 550mAh battery for this project, but there’s no reason why it couldn’t be upgraded to a 18650-sized cell with more than 2000mAh stuffed inside. Add a boost converter to the circuit, and he’ll have the perfect power source for every portable electronics project imaginable.

Hacklet 39: Battery Power

March 27, 2015 by Brian Benchoff 8 Comments

[robin] has a Red Camera (lucky!), an absurdly expensive digital video camera. As you would expect the batteries are also absurdly expensive. What’s the solution? Battery packs from cordless drills.

Cordless drills are interesting pieces of tech that can be easily repurposed; there are huge battery packs in them, big, beefy motors, and enough hardware to build an Automatic Cat Feeder or a motorized bicycle.

What if those old Makita batteries don’t charge? That usually means only one or two cells are dead, not the whole pack. Free LiIon cells, but you need to charge them. Here’s a single cell charger/boost converter that will do the trick.

A problem faced by amateur radio operators around the world is the lack of commercial power. Plugging a portable shack into a wall will work, but for uninterrupted power car batteries are everywhere. How do you combine wall power and car batteries for the best of both worlds? With an In-line battery backup module.

All of the projects above rely on charging a battery through wall power, and sometimes even that is impossible. Solar is where we’re headed, with solar LiPo chargers, and solar LiFe chargers. That’s more than enough to keep a smartphone charged, but if you want to go completely off the grid, you’re going to need something bigger.

[Michel] has been off the power grid 80% of the time since he installed his home PV system a few years ago. How’s he doing it? A literal ton of batteries, huge chargers, and a 5kW inverter.

Electric Bubblegum Board

October 20, 2014 by Marsh 17 Comments

The Mini Maker Faire in Atlanta was packed with exciting builds and devices, but [Andrew’s] Electric Bubblegum Boards stood out from the rest, winning the Editor’s Choice Award. His boards first emerged on Endless Sphere earlier this summer, with the goal of hitting all the usual e-skateboard offerings of speed, range, and weight while dramatically cutting the cost of materials.

At just over 12 pounds, the boards are lightweight and fairly compact, but have enough LiFePO4’s fitted to the bottom to carry a rider 10 miles on a single charge. A Wii Nunchuck controls throttle, cruise control, and a “boost” setting for bursts of speed. The best feature of this e-skateboard, however, is the use of 3D-printed parts. The ABS components not only help facilitate the prototyping process, but also permit a range of customization options. Riders can reprint parts as necessary, or if they want to just change things up.

[Andrew’s] board is nearing the 11th hour over at his Kickstarter page, so swing by to see a production video made for potential backers, or stick around after the break for some quick progress and demo videos.

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MSP430 Alarm Clock Project

July 15, 2013 by Mike Szczys 17 Comments

[Markus] turn his breadboard LED matrix tinkering into an alarm clock which wakes him each morning.

Don’t be fooled by how clean his assembly work is. That’s not a fabbed PCB, it’s a hunk of green protoboard which a lot of point-to-point soldering on the back side. It’s driven by the MSP430 G2452 which is oriented vertically in this image. The two horizonal ICs are 595 shift registers which drive the LED modules.

We already mentioned the cleanliness of his assembly, but there’s one other really cool design element. On the back of the unit is what looks like a battery holder for two AA cells. He’s using just one Lithium Iron Phosphate battery (3.2V) which is in the upper of the two cavities. This let him cut the lower part of the holder at an angle to act as a stand for the clock.

Don’t miss the video which walks us through the user interface. It has what you’d expect from an alarm clock. But there is a really bright white LED which mimics a sunrise clock and it does more than just buzz one note when the thing goes off.

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LiFePO4 Batteries Work Much Better In A Camera Than NiMH

March 23, 2013 by Mike Szczys 13 Comments

SAMSUNG

We agree with [Zapmaker] that Canon cameras chew through nickel metal hydride batteries. But we’re not going to use Alkaline because we think it’s wasteful. His solution is to use a battery that has a higher voltage rating. What you see here is a single lithium iron phosphate cell paired with a dummy cell to increase life between charges.

The reason that NiMH batteries don’t last very long is that they’re only rated at 2.4V. It won’t take long for that voltage to drop below the camera’s cutoff threshold since they didn’t start very high to begin with. But a single LiFePO4 cell has the same form-factor but produces 3.2V and maintains voltage well through it’s discharge cycle.

The size is right, but using one cell won’t work by itself. He built a filler for the other slot which is just a wood dowel with a screw all the way through it. The point was ground down and a bit of foil added to ensure a proper connection. We’d be interested to hear back about how this performs over the long term.

Electric Mountain Board With Glove Control

October 10, 2011 by Brian Benchoff 18 Comments

Last summer, we saw [Andres Guzman]’s electric mountain board tearing around the University of Illinois campus. He’s back again, only this time the board isn’t controlled with a PlayStation controller. [Andres] built a wireless glove to control his mountain board.

An Arduino and power supply is mounted to the glove. A 2.4GHz transceiver serves as the comm link between the glove and board. The speed control is handled by this flex sensor from Sparkfun. With the flex sensor held between the middle and ring fingers, all [Andres] needs to do to apply power is slightly bend his fingers.

There’s also a number of safety features built into the board. To enable power to the boards motor, there’s a dead man switch on the glove underneath the thumb. If [Andres] were to take a nasty spill, he would release the switch and the board would come to a stop. [Andres] also made sure the board would shut down if the wireless link was interrupted. The build seems pretty safe, even if he is tearing around his campus in the video below.

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