[Thomas] and his friends wanted to ring in the new year by setting off some fireworks. To keep a safe distance and have a little fun they built this network controller launcher (translated).
the image on the left shows the build in its unused and pristine state. But by the end of the celebration it look a bit melted and burnt. Still, for the first revision of the system it ended up working pretty well.
We’ve seen several remote fireworks launchers that burn up resistors to light the fuses. But this system is much more reusable. The image on the right shows the heating elements which light the fuses. Younger readers might have no idea what they’re looking at, but every automobile used to come with at least one of these electric cigarette lighters. Just drive 12V through them and they get burning hot relatively quickly. That’s where the car battery on the base comes into play. It is connected to the lighters using some mechanical relays.
In the food container attached to the side of the launcher you’ll find a Raspberry Pi which provides the web connection for the system. [Thomas] wrote code which uses a webpage with some bomb icons as buttons. Check out the video after the break to see him demonstrate how fast one of these lighters will glow red after pressing a button on his smart phone.
Continue reading “Network-controlled fireworks launcher”
This tiny little scratch-built electric tricycle is a insanely powerful. Some might think you don’t need a crash helmet for testing a trike, but seeing the video after the break where [Ben Katz] is flying through a parking garage while slaloming between the support beams proves that this ride has some pep to it.
Looking through the presentation post linked above is fun, but when we started digging though the six build log posts we felt ourselves getting sucked into the project. It’s a delight every step of the way. It started with an aluminum box which will host the two rear wheels, drive train, motor, and battery. [Ben] decided to go with A123 Lithium cells, and after testing to see how many he could fit in the space available he started making choices on the motor and driver circuit. When he finally got his hands on the actual cells for the project he took on the fascinating process of constructing his own battery. Dozens of them were hot glued, then soldered together before being encased by placing them in soda bottles and hitting the plastic with a heat gun. And we haven’t even gotten into the bicycle hub-gear transmission system, disc brakes, differential, chain-drive, and motor… you see what we mean about sucking you in.
Oh, and in case you’re wondering this is not [Ben's] first electric vehicle build. Last year he was showing off his all terrain scooter.
Continue reading “Electric tricycle build log is like hacker crack”
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.
[Kenneth Finnegan] took the focus of a great design and redirected it to solve his own problem. What results is this lead acid battery charger based on the 555 timer. It’s not a top-of-the-line, all the bells and whistles type of charger. But it gets the job done with a readily available IC and no need to code for a microcontroller.
The original idea came from a solar battery charger entered in the 555 timer contest. The main difference in application between that and [Kenneth's] application is the source. A solar array or wind turbine is limited on how much juice it can produce. But mains power can push a shocking (har-har) amount of current if you’re not paying attention. Herein lies the alterations to the circuit design. To control this he’s using a Laptop power supply as an intermediary and only implementing the constant current portion of the tradition 3-stage lead acid charging profile (those stages are explained in his write up).
He did a talk on the charger at his local radio club. You can see the 90-minute video after the break.
Continue reading “555-timer charges lead acid batteries”
Most of what people call batteries are actually cells. All of the common disposable alkaline batteries from AAA to D are single cells. The exception is the 9v battery which actually has six smaller cells inside of it. [Tom] took a look inside three different batteries to see what cells they’re hiding. Since he no longer uses the batteries for their intended purposes the individual cells may find a new life inside of one of his upcoming projects.
The six volt lantern battery on the left has four cells inside of it. This is no surprise since each zinc-carbon cell is rated for 1.5V. There’s not much that can be done with the internals since each cell is made of a carbon rod and zinc electrolyte ooze (rather than being sealed in their own packages).
Moving on to the rechargeable PP3 battery in the middle he finds the 8.4V unit is made up of seven 1.2V nickel-metal hydride cells. Many of them were shot, but we’d love to see one of the intact cells powering something small like a bristlebot.
The final component is an old laptop battery. Inside are an octet of Lithium Ion cells. The majority register 0V, but a few have 0.4V left on them. This is not surprising. We’ve seen power tool packs that have a few bad cells spoil the battery. It’s possible to resurrect a battery by combining good cells from two or more dead units.
[Doctor Bass] needed to do some welding on his electric bicycle. The problem is that he’s never welded before and doesn’t have any tools for it. As you can see, that didn’t stop him. He used a bicycle battery made from reclaimed DeWalt A123 cells to power his diy welding rig.
He has a huge adjustable resistor which is responsible for limiting the current. 80 Amps seems to work the best with the welding rods he’s chosen. It is worth noting that when he shows off each part of the welder (see the clip after the break) the color of the wire used for positive and negative leads is opposite of convention. His positive wiring is black while his ground connection is red.
To get the welding under way he connects a jumper-cable-like clamp to his work piece which serves as the positive electrode. To hold the welding rod he drilled a hole in a pair of vice grip pliers and bolted on the negative lead. This way the end of the welding rod can be clamped in the vice grips while his other hand guides the tip. So far he’s still practicing, but it looks like he’s nearly ready to take on the job at hand.
Continue reading “Welding with over a hundred A123 Lithium cells”
This is a scratch-build meter for measuring the internal resistance of Lithium Polymer cells. [Bleuer Csaba] uses the LiPo cells for RC vehicles and thet take quite a beating from the motors they’re supplying. This means that he only gets about 100-200 cycles out of each cell. To figure out where one is in its life cycle you can measure the internal resistance where a rising resistance indicates greater age. [Bleuer] mentions that you can buy a meter to do this for you, but what fun is that?
Since he’s rolling his own tool he defined his own parameters for the readings. After experimenting with different loads driven for different test periods he was able to extrapolate an equation that estimates the resistance measurement. As you can see in the clip after the break, this happens very fast. All he has to do is connect the cell and press one button. The measurements are made and various data points are displayed on the quartet of 7-segment displays.
Continue reading “LiPo internal resistance measurement tool”