Flashlight Dynamo

An adult in reasonable physical shape can generate the equivalent of 120 to 150 watts of electric bicycles, as a professional athlete is able to generate double that. If we used that energy to light LEDs, could illuminate an entire house.

Although not very practical to use with stationary dynamos to generate electricity (unless you want to be riding all day), using muscle energy to power small devices is a promising branch.The best example is the lights and taillights using dynamos to charge the battery.

They are a risky buy because the quality varies greatly. Many break down quickly or usebatteries that failed to control the quality of the manufacturers (they need to go somewhere, the Chinese do not throw anything out, export all ...;) which hold low.

However, if you can find a model of good quality, can be a good buy. An example of this is $ 5 (sku 3383 in dealextreme).

Here the dynamo is driven by a rope and carries a small battery NI-MH, 3.6V and 80 mAh. LEDs consume only 30 milliwatts each, so the battery lasts more than two hours when fully charged.

The dynamo is capable of generating about 0.2 milliwatt-hours per pull, which means you need about 120 drawn (about 2 to 3 minutes, according to the rush) to load enough for 15 minutes of light and a 1500 pulled (half hour) to get a load almost complete.

At first it seems pretty bad, but in practice until it works, because you end up using the flashlight for a few minutes at a time, which is equivalent to a few pulls. In general ends up being more useful than using a common flashlight with rechargeable batteries (which lose their charge over time), since it is always ready to use.

Another similar idea, but that does not work so well are the chargers USB, where the dynamo is used to power a USB port, where you can connect several shippers. An example of this charger is $ 3 (24036th of DX sku).

The idea is not bad: use the dynamo load cell or pair mp3players via USB without having to use the outlet. The big problem is that the dynamo generates only 0.1 amps of current with a voltage ranging between 4.5 and 6V, according to the speed of rotation.

It has a rudimentary circuit voltage regulation (eliminating the risk of burning the gadgets to burn), but you have to turn the crank with a rotating stable for at least 2 or 3 minutes to be able to increase the battery of a cell in just 1%, or be literally all afternoon to get a full charge.

Perhaps a larger dynamo, which included a small internal battery would work better, but in miniature chargers like this are a waste of time. You can use it to light LEDs or move fans (a good way to show how electricity is generated for children), but if you want an emergency charger, it will be better served by a charger to the battery as the # Useful Gadgets 4.

Unmounting a mini bluetooth transmitter: I spoke earlier of the mini transmitters Bluetooth,which is only slightly larger than the actual USB connector serving as a good option for notebooks without integrated Bluetooth.

However, you may have been curious to understand how they can be as small as a Bluetooth transmitter is a component of relatively complex, with a controller signals, radio, antenna and other components. Past, manufacturers were proud to be able to produce transmitters the size of a matchbox.

The secret of these transmitters in miniature is the use of a circuit board and thin, with the components distributed on both sides. This allows the board to be installed within the connector, using all available space.

Typically, the transmitter would include a metal roof against electromagnetic interference, but as there would be plenty of room for this, the designer opted to simply use your own USB connector metal as a shield.

On one side of the PCB there is only the quartz crystal, the status LED and a handful of resistors, and connector pin USB.

The other side hides the components really interesting. The largest chip, the CSR41B13 is the Bluetooth chipset, which is the real miracle of engineering "in the mini-transmitter. It incorporates the controller, signal processor, radio and other components on a chip that costs less than two dollars. He has worked with voltage of 5V, which enables it to be powered by the USB port itself, without a voltage regulator. The second chip just below it (24BC16) is a chip EEPROM, which stores the firmware. In the corner we have the antenna.

These mini-transmitters impressed not only by the small size, but also by cost. If purchased in retail stores such as the DX they start at $ 2.50, but when purchased in bulk, they can cost $ 1.50. This figure is remarkably low, considering that in theory only the chipset CSR41B13 cost more than that.

How can you sell at that price and still make money? This is a good question.