This project allows any user to charge a smartphone via a micro-USB cable by converting mechanical energy into electrical energy using a small 5 V DC motor.
Nowadays smartphones and phones are daily use gadgets for most people and the necessity to charge it at least 2 times a day might be present if the user requires many functions of the phone,they also charge using micro-USB connections with 5V DC ,so one of the main objectives is to generate 5 V and enough current to charge a battery. We are using is a 3.7 V DC battery which presents no problems to charge at 5V and a circuit to rise the voltage to 5V ,since this battery has a good discharge rate it is also excellent to charge a smartphone.
IMPORTANT NOTE: the project presented via this instructable is a PROTOTYPE, the final version is currently in development
Step 1: Mechanical Features
The power generator mechanism uses the next
1 - High Power 100:1 motor.
2 - 2 gears with the diameter proportion 2:1 between each.
The small gear has to be mounted to the motor, in such way that it turns double as fast as the big one when they are in contact. The big gear is fixed to place to withstand the strong forces that will be handling the rotating lever. Finally, a lever is mounted to the big gear with a somewhat long arm in order to reduce the force that it is necessary to rotate the system.
The body of the system needs to be made of a strong material, strongly glued to its place, allowing the gear to rotate properly and denying it from moving to any direction.
Step 2: Electronic Features
This project consists of a real simple electronic circuit in order to charge our rechargeable battery (and with it, our phone)
By producing mechanical energy, the DC motor provides an output voltage, and therefore, an output current. We know because of testing and some research that with a 5 V potential and 100 mA a rechargeable battery can be charged. The electronic circuit acts as a filter and signal conditioner.
- 4 rectifier diodes (or an integrated diode bridge)
- 1 3.7 Volts rechargeable battery
- 1 ceramic capacitor
- 1 5.1 Volts zener diode (optional)
- two USB A-Type female connectors
- one USB to micro-USB cable
The diodes rectifier eliminates any chance of having negative voltages and harming the battery. The capacitor supresses voltage peaks and the zener diode regulates the output voltage so that the battery does not receive voltage values larger than 5 Volts.
Step 3: Setting it together
Setting the entire system is relatively simple, provided you have a knack for building things and have previously tried soldering. Essentially assembling the PCBs (Printed Circuit Boards) or manually soldered boards is relatively easy considering the circuits utilised have few components
. Furthermore Using multiple USB sockets allows you to maintain capability with the circuits integrated to the portable battery. To do this, simply solder together the corresponding VCC to VCC and GND to GND ports together while soldering the D+ and D- pins to one another on each socket. The + and - terminals from the voltage regulator circuit that is connected to the generator should be connected between the USB sockets (as to charge the battery like if the generator where a USB cable).
Additionally, more components like solar panels may be soldered in the same way to charge the portable battery circuit. Once all components have been properly connected, place the resulting system in a secure container, preferably made from durable material like wood, metal (be sure to leave no exposed wiring in this case) or plastic.
On Step 5 of this instructable the full system performance can be observed in a video.
Step 4: Battery Level Indicator (extra)
For this part the LM3914 Dot-Display integrated circuit is added. This circuit has a supply voltage and a reference voltage, which in this case, is going to be the battery's voltage. The battery used for the project reaches a maximum voltage of 3.7 Volts.
The selection of resistors cause the circuit to turn ONE led on when reference voltage is between 0.7 Volts and 1.6 Volts, TWO leds when 1.7-2.6 and THREE for 2.7-3.7 Volts.
The system is finally connected to a push button on IC's pin #3, which acts as a normally open switch, when the button is pressed, the system turns the corresponding number of leds. It is also important to mention that pin #9 is connected to VCC for the circuit to act in 'bar' mode, this is, all outputs that correspond to the treshold's level or lower turn on. In the other mode (dot) only the 'most significant output' receives a logic '1'.
This part can be included as a bonus simply for knowing the status of your rechargeable battery without usign a multimeter.
Schematic image taken from LM3914 Datasheet
Step 5: Testing
This video shows the system charging the battery (this can be observed on the red indicator LED) and then providing enough enery to charge a Nexus mobile phone.