Giving A Crank Flashlight A Super Capacitor Overhaul

June 21, 2013 by Mike Szczys 25 Comments

crank-flashlight-supercap-overhaul

[Caleb] was given a tiny LED flashlight which has a crank used to charge it. Unfortunately it wasn’t holding a charge, and constant cranking didn’t work very well either. He cracked it open to find a single lithium button cell. Instead of using a drop-in replacement he soldered in his own super capacitor.

The stock device is remarkably simple. It uses a standard DC motor as the generator. It’s connected to the crank using a set of gears, with the two red wires seen above connecting it to the control board. Four diodes make up a bridge rectified and apparently feed directly into the battery. No wonder that cell went kaput!

But this orientation isn’t bad for using capacitors. They can be charged directly and the switch which attaches the LEDs to voltage doesn’t interfere with their operation. The last problem was making room for them in the case. [Caleb] considered a few different approaches, but ended up just heating the plastic enclosure until it could be deformed to make room for the additional parts.

Making Graphene With A DVD Burner

December 21, 2012 by Mike Szczys 64 Comments

A group of researchers have figured out how to produce graphene using a DVD drive. This discovery helps clear the path for mass production of the substance, which was discovered in the late 1980’s. More recently, the 2010 Nobel Prize for Physics was awarded to a team that produced two-dimensional graphene; a substance one just atom thick. One method of doing so used Scotch tape and is mentioned in the video after the break as a technique that works but is not feasible for large-scale production.

The process seen here starts with graphite oxide because it can be suspended in water. This allows a lab technician to evenly distribute the substance on a plastic surface. Note the use of optical discs. The second part of the process involves hitting the dried layer of graphite oxide with a laser. It just so happens that this can be done with a consumer DVD drive. The result is graphene that can be used in circuits and may have potential as a fantastic super-capacitor.

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Print Your Own Supercaps

March 20, 2012 by Adam Munich 125 Comments

[Gil] recently wrote in to tell us about some awesome research going on at UCLA. Apparently by layering some oxidized graphite onto a DVD and tossing it into a lightscribe burner, it’s possible to print your own super capacitors; some pretty high capacity ones at that.

For those that are unaware, supercapcaitors are typically made using two electrolyte soaked, activated carbon plates separated by an ion permeable film. Since activated carbon has an incredible surface area huge energy densities can be reached, in some cases 1kJ/lb.

Laser-formed graphite sponge replaces the activated carbon in the researchers’ printed capacitors. A video after the break discusses the whole process in moderate detail, meanwhile greater detail can be found in their two papers on the subject.

First one to print a transistor gets a bag of mosfets!

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Supercap Lights Your Way In Times Of Need

February 10, 2012 by Mike Szczys 46 Comments

You won’t find [Antoine] stumbling around in the dark. He just finished working on this LED flashlight which draws power from a super-capacitor (translated). He realized that lighting a high-efficiency LED takes so little power that there are many benefits in play when deciding to move away from batteries. When compared to a super capacitor, batteries have a shorter life span, are heavier, and take up more space.

The biggest drawback of a super capacitor in this situation is the low voltage operation. The output will start at 2.7V and drop as the current is discharged. [Antoine] used one of our favorite simple circuits to overcome this issue, the Joule Thief. That circuit is commonly seen paired with an LED in order to boost input voltage to a usable level. That’s precisely what’s going on here.

The final hack in his circuit is the addition of that red LED which you can see in the middle of the board. This takes the place of a Zener diode and drops the charging voltage to a safe level. That indicator light will not come on until the cap is fully topped off. This way it tells you when the device is done charging.

Hackaday Links: November 6th, 2011

November 6, 2011 by Mike Szczys 16 Comments

Build details for Raspberry Pi prototype

With the launch of Raspberry Pi approaching the development team released the details about the prototypes from about five years ago. The board was originally based on an ATmega644 and built on some perfboard.

‘Zero Energy Device’ challenge

We call BS on the title of this one, but the goal of finding devices that don’t use disposable energy sources is a good thing in our book. For instance, can we get more stuff that uses long-life capacitors instead of batteries?

Command adhesive for mounting bulletin boards, etc.

This seems like a no-brainer, but we’ve been using nails to mount bulletin boards and white boards for year. The problem is, when you stick a push-pin in one side, the other side pops off of the nail. [Zhanx] is using adhesive from 3M Command Hooks to keep his stuck to the wall.

Servo-driven gripping hand

[Navic] has been hard at work on this robot hand. There’s few details but he shows it can grip objects under one pound and he’s been taking amperage measurement during testing.

Emergency cellphone charging

It might not have been an emergency this time, but [Chris] did figure out a way to charge his cellphone after the snow storm in New England knocked out his power. He connected to lantern batteries to a 7805 regulator, then patched that into a USB hub to get his phone connected. Not bad in a pinch!

Variable Super Capacitor Battery Provides Power On The Go

April 15, 2011 by Mike Nathan 27 Comments

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Instructable user [EngineeringShock] got sick of buying batteries for his devices all the time and has instead opted to build himself a super capacitor bank that can be used to power common household items.

His “forever” rechargeable capacitor bank is made of two large super capacitors rated at 400 farads apiece. It is charged through a LM317-based charging circuit that is adjustable to allow for slow or fast charging, the latter of which he admits, is slightly dangerous.

Since the super caps are only rated at 2.7 volts, they are wired through a DC-DC booster circuit that allows him to adjust the output voltage from 4.3 v to 34 v. The adjusted voltage is then passed through a digital display that allows him to see what the output voltage is at any time.

He says that the super cap bank can power his computer’s speakers for about two hours before requiring a recharge, which takes just a few short minutes, depending on how he is charging them.

While it’s not exactly cheap, the capacitor bank could be useful for those requiring quick portable power for relatively short periods of time. If we were to build one ourselves, we would likely fit all of the components into a small project box to protect the caps from accidental discharging, and top it off with a couple of solar cells to charge it for free during the day.

Keep reading to see a quick video demonstration of his super cap “battery” in action.

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Add Supercaps To Your Exercise Routine

October 8, 2010 by Mike Szczys 26 Comments

Many exercise machines generate electricity as you pedal or climb in order to run the on-board electronics. Unfortunately if you stop or even slow down too much the juice will die and your exercise program will reset. Wanting to improve on this gotcha, [Mike] cracked open his exercise bike and added some super capacitors.

On the circuit board he found an ATmega128 was in charge of the user interface. He probed the board a little bit and couldn’t find how it was connected to the power regulators. After some additional snooping he found it has its own SOIC regulator separate from the ones that run the display and peripherals. He takes us through the calculations he made before choosing his parts. What he ended up with is a set of three supercaps in series that add about two minutes of juice before the levels drop and the chip resets. The design of the board helped a lot as the high-load electronics (like the LCD screen) are on a separate power bus than the processor.